tyler8611 5/29/2018 7:05 PM
Deluxe Reverb problem
Hi, I've built a deluxe reverb clone and have hit a snag. My screen and plate voltages on the 6v6s are both only 153v. I get a zero reading on pin 8 (through 1 ohm resistors), both mA and mV. I measured and set the negative bias voltage at -35. It's not a tube problem- already swapped another pair with same results.

B+ is 440, then the second node drops all the way down to the 153v. The remaining power caps measure about as they should.

Obviously there's no output, unless I dime channel 1 and get faint crackling notes. Vibrato channel is silent all the way up.

Does this seem like a power cap or maybe transformer problem? I've checked the wiring and solder joints thoroughly.
 
Leo_Gnardo 5/29/2018 7:14 PM
Quote Originally Posted by tyler8611 View Post
Does this seem like a power cap or maybe transformer problem?
Neither. There's a choke between the main B+ and the second power supply node that feeds the 6V6's screen grids. There would have to be something awful wrong with that choke for the screen grid voltage to drop all the way to 153V. Let's measure the resistance between those choke leads. Power OFF of course.

Also possible the hi voltage nodes are wired in an out-of-order way.
 
The Dude 5/29/2018 7:23 PM
I'm confused. You say, "B+ is 440". Then you say, "My screen and plate voltages on the 6v6s are both only 153v" The output tube plate node (B+) is before the choke and goes through the OT directly to the plates. You almost have to have something wired wrong.

[ATTACH=CONFIG]48992[/ATTACH]
 
tyler8611 5/29/2018 7:25 PM
Quote Originally Posted by Leo_Gnardo View Post
Neither. There's a choke between the main B+ and the second power supply node that feeds the 6V6's screen grids. There would have to be something awful wrong with that choke for the screen grid voltage to drop all the way to 153V. Let's measure the resistance between those choke leads. Power OFF of course.

Also possible the hi voltage nodes are wired in an out-of-order way.
Ok I'll do that and report back. Also will check the doghouse again.
 
tyler8611 5/29/2018 7:28 PM
Quote Originally Posted by The Dude View Post
I'm confused. You say, "B+ is 440". Then you say, "My screen and plate voltages on the 6v6s are both only 153v" The output tube plate node (B+) is before the choke and goes through the OT directly to the plates. You almost have to have something wired wrong.

[ATTACH=CONFIG]48992[/ATTACH]
I meant the voltage from pin 8 of the rectifier to the first power cap node. That is 440 and the second node feeding the screens is 153. The OT plate voltage is also 153.
 
tyler8611 5/29/2018 7:33 PM
Quote Originally Posted by Leo_Gnardo View Post
Neither. There's a choke between the main B+ and the second power supply node that feeds the 6V6's screen grids. There would have to be something awful wrong with that choke for the screen grid voltage to drop all the way to 153V. Let's measure the resistance between those choke leads. Power OFF of course.

Also possible the hi voltage nodes are wired in an out-of-order way.
Between the leads is 154 ohms.
 
The Dude 5/29/2018 7:35 PM
Yes. I understand. If you look at "pin 8 of the rectifier to the first power cap node", follow it up through the OT. It connects directly to the tube plates. If you measure 440VDC there, you should also measure it on the plates, unless you have a horribly bad, hot, melted standby switch. Measure DC on both sides of the standby switch. Is it the same on both with the switch closed?
 
tyler8611 5/29/2018 7:36 PM
Quote Originally Posted by tyler8611 View Post
I meant the voltage from pin 8 of the rectifier to the first power cap node. That is 440 and the second node feeding the screens is 153. The OT plate voltage is also 153.
Voltages to ground of course.
 
tyler8611 5/29/2018 7:43 PM
Quote Originally Posted by The Dude View Post
Yes. I understand. If you look at "pin 8 of the rectifier to the first power cap node", follow it up through the OT. It connects directly to the tube plates. If you measure 440VDC there, you should also measure it on the plates, unless you have a horribly bad, hot, melted standby switch. Measure DC on both sides of the standby switch. Is it the same on both with the switch closed?
True and everything is wired correctly. Weird problem.
 
Leo_Gnardo 5/29/2018 8:02 PM
Quote Originally Posted by tyler8611 View Post
True and everything is wired correctly. Weird problem.
True that. It's very weird to have 440V at one end of that choke and 153V at the other. If that's really the case it should be shooting flames. I'm still holding out for a mis-wiring. If you have an electronically knowledgeable friend have them give it a look-see. Sometimes a different set of eyes can pick out what's amiss.
 
The Dude 5/29/2018 8:11 PM
IMO, the problem is before the choke. According to post #1 the plate voltage is also low. The plate voltage is derived "pre-choke". I'd like to know if the same DCV exists on both sides of the standby switch. Then, if we're good there, we see what the voltage is on the OT primary CT. It should be easy to follow the voltage and see where it's not. The B+ caps should be the same electrical point as the plates as far as DC is concerned, yet we have 2 different voltage readings, so I agree- something is not connected properly.
 
galaxiex 5/29/2018 9:17 PM
Don't know if this is your problem, but I replaced the filter caps in the dog house on my 78 SFDR.

When I powered up, something was not right, I never measured any voltages and nothing smoked... but I knew something was "off".

Powered down and checked my work... one of the cap leads I soldered into the eyelet was a bit long, and it missed the insulating card and shorted to the chassis.

Maybe have a look in that area.
 
tyler8611 5/29/2018 10:15 PM
Quote Originally Posted by The Dude View Post
IMO, the problem is before the choke. According to post #1 the plate voltage is also low. The plate voltage is derived "pre-choke". I'd like to know if the same DCV exists on both sides of the standby switch. Then, if we're good there, we see what the voltage is on the OT primary CT. It should be easy to follow the voltage and see where it's not. The B+ caps should be the same electrical point as the plates as far as DC is concerned, yet we have 2 different voltage readings, so I agree- something is not connected properly.
I forgot to mention that I discovered earlier that on standby, the voltage readings were actually normal. Drop happens when I take it off standby. The switch is wired correctly with the leads going exactly where they should. Very strange.

I also measured the resistance of the transformer and choke leads and they were fine. I drained the filter caps and measured those and the readings began around 90k and kept creeping upwards past 150k, so I'm not sure whether that's normal.

I ran a flashlight under the filter cap board- no shorts. I'll have to keep searching.
 
tyler8611 5/29/2018 10:18 PM
Quote Originally Posted by galaxiex View Post
Don't know if this is your problem, but I replaced the filter caps in the dog house on my 78 SFDR.

When I powered up, something was not right, I never measured any voltages and nothing smoked... but I knew something was "off".

Powered down and checked my work... one of the cap leads I soldered into the eyelet was a bit long, and it missed the insulating card and shorted to the chassis.

Maybe have a look in that area.
I thought that could be a possibility also so I looked under with a flashlight and saw nothing grounding out. It's a garolite board on standoffs so I was able to see.
 
The Dude 5/29/2018 10:23 PM
Quote Originally Posted by tyler8611 View Post
I forgot to mention that I discovered earlier that on standby, the voltage readings were actually normal. Drop happens when I take it off standby. The switch is wired correctly with the leads going exactly where they should. Very strange.
Are you saying that, when you have the standby switch closed, your 440V B+ drops at the filter caps?
 
tyler8611 5/29/2018 10:30 PM
Quote Originally Posted by The Dude View Post
Are you saying that, when you have the standby switch closed, your 440V B+ drops at the filter caps?
The 440 B+ doesn't drop, but the second power cap node, 6v6 screens and plates drop down from normal range, while on standby, to abnormally low when switched from standby to play.
 
The Dude 5/29/2018 10:34 PM
Again, please measure the voltage on both sides of the standby switch (switch closed) and tell us what you have. Then, measure the voltage on the center tap of the primary of the output transformer and report.
 
tyler8611 5/29/2018 11:04 PM
Quote Originally Posted by The Dude View Post
Again, please measure the voltage on both sides of the standby switch (switch closed) and tell us what you have. Then, measure the voltage on the center tap of the primary of the output transformer and report.
Ok the voltage to ground from the rectifier side is now 480. No idea why or how it jumped. Voltage on the other side, connected to the choke lead and OT center tap is 156. The remaining filter cap nodes are 127v for the PI and 111 preamp.
 
Enzo 5/29/2018 11:30 PM
Hi

When you check something, please don't tell us it is "fine", please tell us what you measured. We don't know what you consider fine, and we want to know specific values.

You have 440 at the standby switch? OK. What do you have at the OT CT?

To me "second node" is the downhill side of the choke, ie the screens. It bothers me you have the SAME voltage at both plates and screens, even though ther is a choke and transformer between those two places.

What voltages do you get there with power tubes removed?

The standby switch should be on at all times here. ON means closed, the operate position. You should have your 440v on both sides of that switch.
 
pdf64 5/30/2018 3:38 AM
It may be helpful to note that in a parallel thread on TAG, the OP has revealed a 'trickle bypass' mod to the standby arrangement Deluxe Reverb voltages - Page 2 - The Amp Garage
Hence standby mode is not as we would normally know it.
Most amps described as clones aren't; it's way better to provide an accurate schematic, rather than provide text descriptions of deviations to an existing design.

Quote Originally Posted by tyler8611 View Post
Ok the voltage to ground from the rectifier side is now 480. No idea why or how it jumped...
Maybe the mains voltage increased a few V? It's a good idea to monitor the mains Vac whilst undertaking such testing, as all voltages from the PT secondary will be a ratio of the primary voltage.
 
J M Fahey 5/30/2018 4:37 AM
Quote Originally Posted by The Dude View Post
Yes. I understand. If you look at "pin 8 of the rectifier to the first power cap node", follow it up through the OT. It connects directly to the tube plates. If you measure 440VDC there, you should also measure it on the plates, unless you have a horribly bad, hot, melted standby switch. Measure DC on both sides of the standby switch. Is it the same on both with the switch closed?
Quote Originally Posted by tyler8611 View Post
True and everything is wired correctly. Weird problem.
PLEASE-ANSWER-WHAT-YOU-ARE-ASKED
"True" is not an answer.
"everything is wired correctly" is obviously not the case.

EDIT:
PDF64 wrote:
It may be helpful to note that in a parallel thread on TAG, the OP has revealed a 'trickle bypass' mod to the standby arrangement Deluxe Reverb voltages - Page 2 - The Amp Garage
Is that so?
If so, why didnīt you mention it?
Please post the schematic of said "trickle bypass".

And remember:
"Standby ON means switch closed, passing current to the OT and power tubes"

"Standby OFF means switch open, NOT passing current to the OT and power tubes"

Nobody knows what trickle Bypass actually means but just from its name it looks like a BAD idea.
 
tyler8611 5/30/2018 6:47 AM
Quote Originally Posted by pdf64 View Post
It may be helpful to note that in a parallel thread on TAG, the OP has revealed a 'trickle bypass' mod to the standby arrangement Deluxe Reverb voltages - Page 2 - The Amp Garage
Hence standby mode is not as we would normally know it.
Most amps described as clones aren't; it's way better to provide an accurate schematic, rather than provide text descriptions of deviations to an existing design.


Maybe the mains voltage increased a few V? It's a good idea to monitor the mains Vac whilst undertaking such testing, as all voltages from the PT secondary will be a ratio of the primary voltage.
I've used the standby switch trickle bypass mod on a tweed deluxe build, tweed bassman build and princeton reverb build. Never had a single problem with it.

I will check and monitor the mains Vac and provide readings.
 
tyler8611 5/30/2018 6:49 AM
Quote Originally Posted by J M Fahey View Post
PLEASE-ANSWER-WHAT-YOU-ARE-ASKED
"True" is not an answer.
"everything is wired correctly" is obviously not the case.

EDIT:


Is that so?
If so, why didnīt you mention it?
Please post the schematic of said "trickle bypass".

And remember:
"Standby ON means switch closed, passing current to the OT and power tubes"

"Standby OFF means switch open, NOT passing current to the OT and power tubes"

Nobody knows what trickle Bypass actually means but just from its name it looks like a BAD idea.
This reminds me of that other forum. Jesus.
 
tyler8611 5/30/2018 7:11 AM
I'll be providing exact detailed measurements all at once asap. I appreciate you guys.
 
tyler8611 5/30/2018 7:52 AM
Quote Originally Posted by tyler8611 View Post
Ok the voltage to ground from the rectifier side is now 480. No idea why or how it jumped. Voltage on the other side, connected to the choke lead and OT center tap is 156. The remaining filter cap nodes are 127v for the PI and 111 preamp.
I think several of you guys may have missed this response. This is both sides of standby, switch closed. 480 on one side, 156 other.
 
tyler8611 5/30/2018 7:55 AM
And I can certainly remove the trickle bypass if anyone thinks it's making this more difficult. But like I said, I've always used it. I think it's a sensible, but obviously not mandatory mod.
 
pdf64 5/30/2018 7:59 AM
Quote Originally Posted by tyler8611 View Post
I've used the standby switch trickle bypass mod...
Have you made any other deviations from the DR AB763 schematic and layout? http://schems.com/schematicheaven.ne...b763_schem.pdf
Please take a bit of time and review it carefully against your build.
We'll assume that a grounded mains cable and chassis have been used, and the death cap and switch omitted, unless you say otherwise.

Quote Originally Posted by tyler8611 View Post
I think several of you guys may have missed this response. This is both sides of standby, switch closed. 480 on one side, 156 other.
There may be something wrong with the switch.
I suggest that it is removed from the circuit (at least that will remove terminology confusion), and that you then power up via a light bulb limiter.
 
tyler8611 5/30/2018 8:20 AM
Quote Originally Posted by pdf64 View Post
Have you made any other deviations from the DR AB763 schematic and layout? http://schems.com/schematicheaven.ne...b763_schem.pdf
Please take a bit of time and review it carefully against your build.
We'll assume that a grounded mains cable and chassis have been used, and the death cap and switch omitted, unless you say otherwise.


There may be something wrong with the switch.
I suggest that it is removed from the circuit (at least that will remove terminology confusion), and that you then power up via a light bulb limiter.
Deviations: 1 ohm resistors from pin 8 to ground on the 6v6s, a zener diode string to pull down an overvoltaged PT (also have zeners in my tweed deluxe), 100 ohm resistors on the pilot since my PT lacks a center tap, and copper bus preamp grounding.

I don't have a light bulb limiter but I probably do have another new switch that I can substitute. I will check my parts bin.
 
Leo_Gnardo 5/30/2018 8:59 AM
Quote Originally Posted by tyler8611 View Post
Deviations: a zener diode string to pull down an overvoltaged PT
Are those zeners between hi voltage winding center tap and ground? We had a recent thread where that arrangement caused the bias supply to overcharge = excessively high bias voltage. Why? because the current path through the bias supply presented a lower impedance than the current path through the zeners, causing the bias supply to act in an unexpected way. (If there was an entirely separate winding for the bias supply, not just a tap on a hi voltage winding, it wouldn't be a problem.) This isn't a problem with a tweed Deluxe because it is self-biased, iow has no negative voltage supply for fixed bias operation.

This may explain one reason for some of your Deluxe's misbehavior.

Another, if the meaning of "standby" is inverted, and you have a trickle resistor to partially charge the power supply, it would be expected to see 440V one side of the standby switch and some lower voltage say 153 on the other, when the switch is open. When the switch contacts are closed, the same voltage will exist on both switch terminals.
 
tyler8611 5/30/2018 9:39 AM
Quote Originally Posted by Leo_Gnardo View Post
Are those zeners between hi voltage winding center tap and ground? We had a recent thread where that arrangement caused the bias supply to overcharge = excessively high bias voltage. Why? because the current path through the bias supply presented a lower impedance than the current path through the zeners, causing the bias supply to act in an unexpected way. (If there was an entirely separate winding for the bias supply, not just a tap on a hi voltage winding, it wouldn't be a problem.) This isn't a problem with a tweed Deluxe because it is self-biased, iow has no negative voltage supply for fixed bias operation.

This may explain one reason for some of your Deluxe's misbehavior.

Another, if the meaning of "standby" is inverted, and you have a trickle resistor to partially charge the power supply, it would be expected to see 440V one side of the standby switch and some lower voltage say 153 on the other, when the switch is open. When the switch contacts are closed, the same voltage will exist on both switch terminals.
Yes, they're between center tap and ground. There is a separate blue 50v winding for the bias supply.

I hear what you're saying on the standby, but somehow the reverse is happening. Doesn't make sense because the standby wires are going to their proper lugs on the switch. I will have to try a new one.
 
Leo_Gnardo 5/30/2018 10:07 AM
Quote Originally Posted by tyler8611 View Post
Yes, they're between center tap and ground. There is a separate blue 50v winding for the bias supply.
Is that an entirely separate winding OR a tap on the hi voltage winding? Most transformers intended for Deluxe have the tap. I say most because I haven't seen 'em all, maybe somebody makes a Deluxe power transformer with an entirely separate bias winding.

I hear what you're saying on the standby, but somehow the reverse is happening. Doesn't make sense because the standby wires are going to their proper lugs on the switch. I will have to try a new one.
If the "sense" of the standby function is inverted then a new switch won't help. Easy enough to apply an ohmmeter & find out which direction to point the bat so that the switch is closed; when the meter reads zero ohms, that's the "operate" position and should allow current to pass thru the power supply to run the amp. Yes it's a bit confusing: Fender and lots of other companies print "standby" on the chassis so that when the bat is pointed to the lettering, that's the operate position, and bat away from the lettering is amp on standby, iow not passing signal. Might be all you need to do is invert the switch position and that's that.
 
pdf64 5/30/2018 10:46 AM
I think Leo's hunch is right, the zeners may be screwing up the bias supply.
I suggest to take them out of circuit and review.
I think that a light bulb limiter is second only to a multimeter as being most important resource on a tech's bench.
I suggest to build one before proceeding further.
 
g1 5/30/2018 12:44 PM
Quote Originally Posted by tyler8611 View Post
Doesn't make sense because the standby wires are going to their proper lugs on the switch. I will have to try a new one.
Don't go by the looks of the lugs on the standby switch, measure resistance. Zero ohms is the closed position.
 
tyler8611 5/30/2018 1:30 PM
Quote Originally Posted by Leo_Gnardo View Post
Is that an entirely separate winding OR a tap on the hi voltage winding? Most transformers intended for Deluxe have the tap. I say most because I haven't seen 'em all, maybe somebody makes a Deluxe power transformer with an entirely separate bias winding.



If the "sense" of the standby function is inverted then a new switch won't help. Easy enough to apply an ohmmeter & find out which direction to point the bat so that the switch is closed; when the meter reads zero ohms, that's the "operate" position and should allow current to pass thru the power supply to run the amp. Yes it's a bit confusing: Fender and lots of other companies print "standby" on the chassis so that when the bat is pointed to the lettering, that's the operate position, and bat away from the lettering is amp on standby, iow not passing signal. Might be all you need to do is invert the switch position and that's that.
It's the one here: Fender Power Transformer, Deluxe, Deluxe Reverb, Tweed Tremolux, 125P23B, 025130, 041316, 120V

And you were right about me stupidly forgetting the direction of the standby switch. Unbelievable. Haven't dealt with blackface amps in a long time. Totally slipped my mind!

Now, the problem is the bias is only 4 mA max. So the zeners may indeed be causing this to happen. Currently, the bias tail resistor is 10k. The range resistor, which I may try changing next, is the standard 470 ohm. I was thinking of upping it to 1.5k, which was the next highest metal oxide resistor I could find.

Then again, maybe I should go ahead and remove the zeners. I'll let you guys chime in.
 
tyler8611 5/30/2018 1:32 PM
Quote Originally Posted by pdf64 View Post
I think Leo's hunch is right, the zeners may be screwing up the bias supply.
I suggest to take them out of circuit and review.
I think that a light bulb limiter is second only to a multimeter as being most important resource on a tech's bench.
I suggest to build one before proceeding further.
Thanks I will look into that.
 
Leo_Gnardo 5/30/2018 2:26 PM
Quote Originally Posted by tyler8611 View Post
Then again, maybe I should go ahead and remove the zeners. I'll let you guys chime in.
Ring-a-ding-ding, chiming we are! Sounds like progress, good. Zeners in the hi voltage center tap line are almost certainly forcing the bias voltage to be greater than it should be. More negative voltage that is. You could bridge them with a clip lead instead of eliminating them, until you're sure of what you want to do. With the zeners out of the way I'll bet you can set your bias to some more normal current draw and that will pull your main hi voltage down to what it should be. If the amp starts behaving as we expect then it's time to nix the zeners entirely.
 
tyler8611 5/30/2018 7:03 PM
Quote Originally Posted by Leo_Gnardo View Post
Ring-a-ding-ding, chiming we are! Sounds like progress, good. Zeners in the hi voltage center tap line are almost certainly forcing the bias voltage to be greater than it should be. More negative voltage that is. You could bridge them with a clip lead instead of eliminating them, until you're sure of what you want to do. With the zeners out of the way I'll bet you can set your bias to some more normal current draw and that will pull your main hi voltage down to what it should be. If the amp starts behaving as we expect then it's time to nix the zeners entirely.
Ok cool so bridge or get rid of the zeners and not mess with the range resistor?
 
tyler8611 5/30/2018 10:26 PM
So I unsoldered and grounded the center tap and left the bias arrangement per schematic. Switched it on (standby open) and while I was at it took a measurement of the B+ coming off the rectifier. It eventually reached 497v, and a few minutes later, exactly 500.

I took it off standby and it immediately began motorboating and the tubes were glowing blue. They measured 17 mA. I turned the bias pot and there was no change in the reading. I figured that may be bad and have another to replace it.

Last thing I did was measure the B+ and it was 404v. I should have measured everything but I couldn't take the motorboating anymore. So next is change the bias pot and maybe the tail resistor, and if that doesn't work I'll try to see if it's the tubes.
 
pdf64 5/31/2018 2:03 AM
The bias pot operation should be able to be verified without the power tubes in place, or with them in but with the amp in standby mode, eg measure the Vdc on power tubes pin 5 whilst rotating the bias control over its range.
Motorboating should be able to be stopped by removing the tube in V6, the LTP phase splitter, with negligible effect on the power tube idle conditions.
 
tyler8611 5/31/2018 9:03 AM
Quote Originally Posted by pdf64 View Post
The bias pot operation should be able to be verified without the power tubes in place, or with them in but with the amp in standby mode, eg measure the Vdc on power tubes pin 5 whilst rotating the bias control over its range.
Motorboating should be able to be stopped by removing the tube in V6, the LTP phase splitter, with negligible effect on the power tube idle conditions.
Thanks I'll try it and report back.
 
tyler8611 5/31/2018 12:59 PM
Quote Originally Posted by pdf64 View Post
The bias pot operation should be able to be verified without the power tubes in place, or with them in but with the amp in standby mode, eg measure the Vdc on power tubes pin 5 whilst rotating the bias control over its range.
Motorboating should be able to be stopped by removing the tube in V6, the LTP phase splitter, with negligible effect on the power tube idle conditions.
Just now I took measurements with the tubes installed since they were already in there. Left it in standby and took pin 5 readings, which did change as I moved the bias pot. So it's working. I left it at -35v.

Now I'll remove the 6v6s and the phase splitter as you advised and then take the measurements with standby closed.
 
tyler8611 5/31/2018 1:29 PM
Quote Originally Posted by tyler8611 View Post
Just now I took measurements with the tubes installed since they were already in there. Left it in standby and took pin 5 readings, which did change as I moved the bias pot. So it's working. I left it at -35v.

Now I'll remove the 6v6s and the phase splitter as you advised and then take the measurements with standby closed.
I realized what you were saying about the phase splitter- take it out with the 6v6s in. Anyway, with all but 6v6s installed, I took voltage readings as follows:

B+: 480v
Screens: 477v
PI: 382v
Preamp: 317v

V1 pin 1: 211v
V1 pin 6: 221v

V2 pin 1: 199v
V2 pin 6: 192v

V3 pin 1: 469v
V3 pin 6: 469v

V4 pin 1: 202v
V4 pin 6: 191v

V5 pin 1: 393v
V5 pin 6: 471v

V6 pin 1: 215v
V6 pin 6: 252v

I checked the preamp cathodes and all except vibrato tube (no reading) and phase splitter (forgot to check) aligned with schematic voltages.

So next I will measure with the 6v6s installed and the phase splitter removed.
 
tyler8611 5/31/2018 8:17 PM
Quote Originally Posted by pdf64 View Post
The bias pot operation should be able to be verified without the power tubes in place, or with them in but with the amp in standby mode, eg measure the Vdc on power tubes pin 5 whilst rotating the bias control over its range.
Motorboating should be able to be stopped by removing the tube in V6, the LTP phase splitter, with negligible effect on the power tube idle conditions.
Ok just checked it with phase splitter removed. No motorboating, thankfully. The max current I could get was 17mA. That is with standard 10k pot/10k tail resistor and 470 ohm range. At this setting the negative voltage is -23. So I suppose some resistor changes are in order. And hopefully the motorboating issue will also be resolved.
 
tyler8611 5/31/2018 8:21 PM
Also, the B+ was 433, screens 429, PI 365, preamp 304. Preamp plates still running pretty high but maybe they'll drop when the bias is set right.
 
tyler8611 5/31/2018 9:28 PM
Would it be preferable to increase the range resistor value first? I have a 1.5k I can substitute.
 
Leo_Gnardo 5/31/2018 9:39 PM
Quote Originally Posted by tyler8611 View Post
Also, the B+ was 433, screens 429, PI 365, preamp 304. Preamp plates still running pretty high but maybe they'll drop when the bias is set right.
Yay, those voltages are much more in line with what we expect, even the preamp node. Last we saw, bias current was 17 mA which is just a pinch low but still good. OTOH bias voltage at -23V, if that is what you're measuring at pin 5 of your 6V6's, that is unusually low. Makes me think the 6V6's are way off in a far corner of the usual emissivity we expect. Either they're very "hard" tubes, or they've been baked to death by having been way overheated. I'd expect a bias voltage between -30 and -40V, current say 18 to 25 mA per 6V6. FWIW I find JJ's been making the toughest 6V6 for some years now. They seem to put up with use & abuse that wreck EH/TungSol or any China made ones.
 
g1 5/31/2018 9:40 PM
Are you sure about your 17mA idle current measurement?
You said this was with -23V bias. Fender schem. shows -35V bias and with lower plate voltage. To me, that seems it would give much colder bias than what you have.
Regardless, with 17mA and 430V plate, you are idling around 60% of the 12W rating for 6V6. How hot do you want to go?
 
tyler8611 5/31/2018 9:46 PM
Quote Originally Posted by Leo_Gnardo View Post
Yay, those voltages are much more in line with what we expect, even the preamp node. Last we saw, bias current was 17 mA which is just a pinch low but still good. OTOH bias voltage at -23V, that is unusually low. Makes me think the 6V6's are way off in a far corner of the usual emissivity we expect. Either they're very "hard" tubes, or they've been baked to death by having been way overheated. I'd expect a bias voltage between -30 and -40V, current say 18 to 25 mA per 6V6. FWIW I find JJ's been making the toughest 6V6 for some years now. They seem to put up with use & abuse that wreck EH/TungSol or any China made ones.
They're JJs rated 26. As I understand that's kinda lower than average. JJs are the only 6v6s I've ever gotten along with, besides the RCA blackplates in my tweed deluxe.

Do you think moving the range resistor value up is a good first move to try to get the bias current and negative voltage closer to normal?
 
tyler8611 5/31/2018 9:53 PM
Quote Originally Posted by g1 View Post
Are you sure about your 17mA idle current measurement?
You said this was with -23V bias. Fender schem. shows -35V bias and with lower plate voltage. To me, that seems it would give much colder bias than what you have.
Regardless, with 17mA and 430V plate, you are idling around 60% of the 12W rating for 6V6. How hot do you want to go?
Yep the hottest I could get was 17ma and the neg voltage was -23. 60-65% is probably the range I want to go. No more than 70 obviously. I will try to hit a sweet spot. I think the JJs are rated 14W but I'm not positive on that.
 
tyler8611 5/31/2018 10:08 PM
I was kinda concerned because I noticed earlier that my vib channel volume was for some reason up around 2-3, so I did this again just to be sure.

No phase splitter:

B+ 435
Screens 432
PI 368
Preamp 312

Neg voltage -23

Max bias: 13.8 and 14.2
 
tyler8611 5/31/2018 10:15 PM
Also concerning is the fact that B+ is going over 500v on standby- more than what the caps are rated for.
 
tyler8611 5/31/2018 10:23 PM
Quote Originally Posted by g1 View Post
Are you sure about your 17mA idle current measurement?
You said this was with -23V bias. Fender schem. shows -35V bias and with lower plate voltage. To me, that seems it would give much colder bias than what you have.
Regardless, with 17mA and 430V plate, you are idling around 60% of the 12W rating for 6V6. How hot do you want to go?
Using the weber bias calculator I get 43% dissipation, assuming the JJs are 14w.
 
Leo_Gnardo 5/31/2018 10:23 PM
Quote Originally Posted by tyler8611 View Post
They're JJs rated 26. As I understand that's kinda lower than average. JJs are the only 6v6s I've ever gotten along with, besides the RCA blackplates in my tweed deluxe.

Do you think moving the range resistor value up is a good first move to try to get the bias current and negative voltage closer to normal?
I'd rather see another pair of 6V6's. For the time being you could drop the bias voltage a bit by paralleling say a 47K resistor across the 10K to ground, but we're in scary low territory here. Be prepared to remove that parallel resistor for a different set of output tubes.

Agree with the 6V6 brand choices. Old Sylvanias can be pretty good too.

Rated "26" on somebody's test rig. Of course tube vendors don't much talk about what voltages they apply to tubes under test, that's par for the course. If 26 is well lower than average, find out what's average and get a pair of those. It's not right to panel-beat output tubes into yielding good current figures by running the bias so low. Doing so has other effects, including severely limiting your clean headroom.

When you get around to measuring output power, I've seen healthy Deluxes range between 13 and 22 watts at clip. Don't be disappointed if it's near the low end. If the amp sounds robust when played that's close enough for rock 'n roll.

Hi voltage over 500 on standby, hmmm, how much over. 5 or 10 V, no problem. Just don't leave it on standby for extended periods. There's a 5AR4/GZ34 rectifier, right? That's a slow warmup type - it's actually safe to skip the so called warmup on initial switch on. Hi voltage won't be up to full for 15-20 seconds anyway. The overvoltage problem will be in evidence when you switch to standby with the amp warmed up. Also, it might be half an idea to use a 5Y3 instead, a "real" one, not the Russian made ones that deliver too much high voltage. 5Y3 aren't as efficient as GZ34, they'll leave you with a lower B+, a more relaxed sound, less to worry about. A bit less power but no biggie unless you're determined to get every last watt you can.
 
tyler8611 5/31/2018 10:39 PM
Quote Originally Posted by Leo_Gnardo View Post
I'd rather see another pair of 6V6's. For the time being you could drop the bias voltage a bit by paralleling say a 47K resistor across the 10K to ground, but we're in scary low territory here. Be prepared to remove that parallel resistor for a different set of output tubes.

Agree with the 6V6 brand choices. Old Sylvanias can be pretty good too.

Rated "26" on somebody's test rig. Of course tube vendors don't much talk about what voltages they apply to tubes under test, that's par for the course. If 26 is well lower than average, find out what's average and get a pair of those. It's not right to panel-beat output tubes into yielding good current figures by running the bias so low. Doing so has other effects, including severely limiting your clean headroom.

When you get around to measuring output power, I've seen healthy Deluxes range between 13 and 22 watts at clip. Don't be disappointed if it's near the low end. If the amp sounds robust when played that's close enough for rock 'n roll.
Ok I have another healthy pair of JJs (labeled 23) that I can try. If that doesn't succeed, raising the tail resistor value would be the way to go? Parallel a 47k with the 10k?
 
tyler8611 5/31/2018 10:41 PM
Quote Originally Posted by Leo_Gnardo View Post
I'd rather see another pair of 6V6's. For the time being you could drop the bias voltage a bit by paralleling say a 47K resistor across the 10K to ground, but we're in scary low territory here. Be prepared to remove that parallel resistor for a different set of output tubes.

Agree with the 6V6 brand choices. Old Sylvanias can be pretty good too.

Rated "26" on somebody's test rig. Of course tube vendors don't much talk about what voltages they apply to tubes under test, that's par for the course. If 26 is well lower than average, find out what's average and get a pair of those. It's not right to panel-beat output tubes into yielding good current figures by running the bias so low. Doing so has other effects, including severely limiting your clean headroom.

When you get around to measuring output power, I've seen healthy Deluxes range between 13 and 22 watts at clip. Don't be disappointed if it's near the low end. If the amp sounds robust when played that's close enough for rock 'n roll.

Hi voltage over 500 on standby, hmmm, how much over. 5 or 10 V, no problem. Just don't leave it on standby for extended periods. There's a 5AR4/GZ34 rectifier, right? That's a slow warmup type - it's actually safe to skip the so called warmup on initial switch on. Hi voltage won't be up to full for 15-20 seconds anyway. The overvoltage problem will be in evidence when you switch to standby with the amp warmed up. Also, it might be half an idea to use a 5Y3 instead, a "real" one, not the Russian made ones that deliver too much high voltage. 5Y3 aren't as efficient as GZ34, they'll leave you with a lower B+, a more relaxed sound, less to worry about. A bit less power but no biggie unless you're determined to get every last watt you can.
It got up to 503v. I do have a NOS 5Y3 as well as a NOS 5U4GB, which the PT can handle.
 
tyler8611 6/1/2018 7:19 AM
Quote Originally Posted by Leo_Gnardo View Post
I'd rather see another pair of 6V6's. For the time being you could drop the bias voltage a bit by paralleling say a 47K resistor across the 10K to ground, but we're in scary low territory here. Be prepared to remove that parallel resistor for a different set of output tubes.

Agree with the 6V6 brand choices. Old Sylvanias can be pretty good too.

Rated "26" on somebody's test rig. Of course tube vendors don't much talk about what voltages they apply to tubes under test, that's par for the course. If 26 is well lower than average, find out what's average and get a pair of those. It's not right to panel-beat output tubes into yielding good current figures by running the bias so low. Doing so has other effects, including severely limiting your clean headroom.

When you get around to measuring output power, I've seen healthy Deluxes range between 13 and 22 watts at clip. Don't be disappointed if it's near the low end. If the amp sounds robust when played that's close enough for rock 'n roll.

Hi voltage over 500 on standby, hmmm, how much over. 5 or 10 V, no problem. Just don't leave it on standby for extended periods. There's a 5AR4/GZ34 rectifier, right? That's a slow warmup type - it's actually safe to skip the so called warmup on initial switch on. Hi voltage won't be up to full for 15-20 seconds anyway. The overvoltage problem will be in evidence when you switch to standby with the amp warmed up. Also, it might be half an idea to use a 5Y3 instead, a "real" one, not the Russian made ones that deliver too much high voltage. 5Y3 aren't as efficient as GZ34, they'll leave you with a lower B+, a more relaxed sound, less to worry about. A bit less power but no biggie unless you're determined to get every last watt you can.
Oh forgot to answer- yes it's a JJ GZ34. A rare new production rectifier that actually works well.
 
tyler8611 6/1/2018 11:23 AM
Quote Originally Posted by Leo_Gnardo View Post
I'd rather see another pair of 6V6's. For the time being you could drop the bias voltage a bit by paralleling say a 47K resistor across the 10K to ground, but we're in scary low territory here. Be prepared to remove that parallel resistor for a different set of output tubes.

Agree with the 6V6 brand choices. Old Sylvanias can be pretty good too.

Rated "26" on somebody's test rig. Of course tube vendors don't much talk about what voltages they apply to tubes under test, that's par for the course. If 26 is well lower than average, find out what's average and get a pair of those. It's not right to panel-beat output tubes into yielding good current figures by running the bias so low. Doing so has other effects, including severely limiting your clean headroom.

When you get around to measuring output power, I've seen healthy Deluxes range between 13 and 22 watts at clip. Don't be disappointed if it's near the low end. If the amp sounds robust when played that's close enough for rock 'n roll.

Hi voltage over 500 on standby, hmmm, how much over. 5 or 10 V, no problem. Just don't leave it on standby for extended periods. There's a 5AR4/GZ34 rectifier, right? That's a slow warmup type - it's actually safe to skip the so called warmup on initial switch on. Hi voltage won't be up to full for 15-20 seconds anyway. The overvoltage problem will be in evidence when you switch to standby with the amp warmed up. Also, it might be half an idea to use a 5Y3 instead, a "real" one, not the Russian made ones that deliver too much high voltage. 5Y3 aren't as efficient as GZ34, they'll leave you with a lower B+, a more relaxed sound, less to worry about. A bit less power but no biggie unless you're determined to get every last watt you can.
I also have an RCA 5V4GA. Not sure about the max input capacitance on that one though.

A bit less power is ok. As long as I get the tubes biased where they're supposed to be and the negative voltage closer to schematic.

Also hope the motorboating doesn't return. I guess that might indicate a bad coupling cap somewhere.
 
tyler8611 6/1/2018 10:09 PM
Quote Originally Posted by Leo_Gnardo View Post
I'd rather see another pair of 6V6's. For the time being you could drop the bias voltage a bit by paralleling say a 47K resistor across the 10K to ground, but we're in scary low territory here. Be prepared to remove that parallel resistor for a different set of output tubes.

Agree with the 6V6 brand choices. Old Sylvanias can be pretty good too.

Rated "26" on somebody's test rig. Of course tube vendors don't much talk about what voltages they apply to tubes under test, that's par for the course. If 26 is well lower than average, find out what's average and get a pair of those. It's not right to panel-beat output tubes into yielding good current figures by running the bias so low. Doing so has other effects, including severely limiting your clean headroom.

When you get around to measuring output power, I've seen healthy Deluxes range between 13 and 22 watts at clip. Don't be disappointed if it's near the low end. If the amp sounds robust when played that's close enough for rock 'n roll.

Hi voltage over 500 on standby, hmmm, how much over. 5 or 10 V, no problem. Just don't leave it on standby for extended periods. There's a 5AR4/GZ34 rectifier, right? That's a slow warmup type - it's actually safe to skip the so called warmup on initial switch on. Hi voltage won't be up to full for 15-20 seconds anyway. The overvoltage problem will be in evidence when you switch to standby with the amp warmed up. Also, it might be half an idea to use a 5Y3 instead, a "real" one, not the Russian made ones that deliver too much high voltage. 5Y3 aren't as efficient as GZ34, they'll leave you with a lower B+, a more relaxed sound, less to worry about. A bit less power but no biggie unless you're determined to get every last watt you can.
I paralleled the 47k with the 10k and bias current 14.3 max. Looks like the resistance has to even lower on the pot.
 
pdf64 6/2/2018 3:35 AM
I wonder if something is wacky; with respect to circuit common 0V, what are the actual measured Vdc at the power tubes' terminals 3, 4, 5 and 8 at idle, without a tube in V6 socket.
 
Tom Phillips 6/2/2018 9:03 AM
I sense a basic misunderstanding.
Quote Originally Posted by tyler8611 View Post
...As long as I get the tubes biased where they're supposed to be and the negative voltage closer to schematic...
.
You are saying that you want to bias your 6V6s hotter. I.e. more bias current. At the same time you say you are trying to make the bias voltage more negative. Those are incompatible goals. The -35V shown on the schematic is just a guideline reference value. Furthermore, it was based on the original tube brands used 50 years ago with the amp operating at the line voltages of the day. You need to set the bias voltage "less negative" to achieve hotter bias or use different power tubes.

As stated above I agree that 17ma at your plate voltage may be fine. How does the amp sound at that setting? Listen with your ears not your DVM.
 
tyler8611 6/2/2018 10:23 AM
Quote Originally Posted by pdf64 View Post
I wonder if something is wacky; with respect to circuit common 0V, what are the actual measured Vdc at the power tubes' terminals 3, 4, 5 and 8 at idle, without a tube in V6 socket.
I will check that again. I posted those values previously when there was only a 10k tail resistor on the bias pot.
 
tyler8611 6/2/2018 10:41 AM
Quote Originally Posted by Tom Phillips View Post
I sense a basic misunderstanding.
You are saying that you want to bias your 6V6s hotter. I.e. more bias current. At the same time you say you are trying to make the bias voltage more negative. Those are incompatible goals. The -35V shown on the schematic is just a guideline reference value. Furthermore, it was based on the original tube brands used 50 years ago with the amp operating at the line voltages of the day. You need to set the bias voltage "less negative" to achieve hotter bias or use different power tubes.

As stated above I agree that 17ma at your plate voltage may be fine. How does the amp sound at that setting? Listen with your ears not your DVM.
You're right, I gotcha. They are indeed incompatible. I was too focused on aiming for schematic range. Is there any harm in negative voltage that low?

I did play through both channels last night. The normal channel sounded good. Worked normally. Vibrato was low volume but I didn't have the reverb driver or recovery installed because I had traced the motorboating to the reverb recovery stage. So I will have to change caps there or simply touch up a solder joint, although they looked good to me. It's either the .1 coupling cap or cathode bypass. It's not the tube.

Just out of curiosity, how do you check caps for leakage in the circuit? I never got nailed that down for sure. Then again never had a leaky cap.

Oh just for laughs, last night I found out my tweed deluxe picks up bluetooth. Nice bonus feature. That'll be the next mission- finding out how to prevent that. I wonder if the same trick used to eliminate RF would work?
 
Leo_Gnardo 6/2/2018 10:50 AM
Quote Originally Posted by tyler8611 View Post
You're right, I gotcha. They are indeed incompatible. I was too focused on aiming for schematic range. Is there any harm in negative voltage that low?

- - - - -

Oh just for laughs, last night I found out my tweed deluxe picks up bluetooth. Nice bonus feature. That'll be the next mission- finding out how to prevent that. I wonder if the same trick used to eliminate RF would work?
With the bias voltage so low, you run the risk of trying to force the output tubes' control grids positive with a lower than normal signal level. That will result in early onset of clipping distortion. Might not be the worst thing in the world, "if it sounds good it is good" still works.

Yes, any of the usual RF suppression techniques can be used in your tweed Deluxe. Many of these have no shield on the back side of the amp, and even the ones that have metal inside the back cover, don't have that metal grounded. That's where I'd start. And these days it seems cell phone chatter finds its way into practically every amp somehow.
 
tyler8611 6/2/2018 11:34 AM
Quote Originally Posted by pdf64 View Post
I wonder if something is wacky; with respect to circuit common 0V, what are the actual measured Vdc at the power tubes' terminals 3, 4, 5 and 8 at idle, without a tube in V6 socket.
Did this just now. No V6:

Pin 3: 403, 405

Pin 4: 405

Pin 5: -20.9, -21

Pin 8: 15.9 mA (64.2 mV)
. 16.2 mA (65 mV)
 
tyler8611 6/2/2018 11:45 AM
Quote Originally Posted by Leo_Gnardo View Post
With the bias voltage so low, you run the risk of trying to force the output tubes' control grids positive with a lower than normal signal level. That will result in early onset of clipping distortion. Might not be the worst thing in the world, "if it sounds good it is good" still works.

Yes, any of the usual RF suppression techniques can be used in your tweed Deluxe. Many of these have no shield on the back side of the amp, and even the ones that have metal inside the back cover, don't have that metal grounded. That's where I'd start. And these days it seems cell phone chatter finds its way into practically every amp somehow.
Yeah, as long as it sounds good and is operating like it should, I'm happy. But I wanna try to identify whether there's an issue with the bias circuit that should be corrected. Maybe it's the PT 0V wiring for instance, as someone mentioned. We'll see.

The interference - I used to have an apple but switch to samsung just for the hell of it. This never happened with the apple. I was thinking of installing in the tweed deluxe a suppressor at the input, but I'd have to look up the best way to do that.
 
tyler8611 6/2/2018 11:47 AM
Quote Originally Posted by tyler8611 View Post
Yeah, as long as it sounds good and is operating like it should, I'm happy. But I wanna try to identify whether there's an issue with the bias circuit that should be corrected. Maybe it's the PT 0V wiring for instance, as someone mentioned. We'll see.

The interference - I used to have an apple but switch to samsung just for the hell of it. This never happened with the apple. I was thinking of installing in the tweed deluxe a suppressor at the input, but I'd have to look up the best way to do that.
I checked and it does have grounded shielding on the back.
 
tyler8611 6/2/2018 6:56 PM
I have an isolated problem with the V4 reverb recovery circuit causing motorboating. I substituted all the coupling caps and cathode bypass cap associated with V4. Nothing worked and I've tried four different 12AX7s- all the same result. I went in resoldered every point in the circuit.

Could it be a bad filter cap?
 
Tom Phillips 6/2/2018 7:21 PM
Yes. Most likely a bad fiter (decoupling) cap or bad grounding.
 
tyler8611 6/3/2018 7:58 AM
 
tyler8611 6/3/2018 11:53 AM
Quote Originally Posted by Tom Phillips View Post
Yes. Most likely a bad fiter (decoupling) cap or bad grounding.
Thought so. I'll replace that particular power cap and check the grounding joints.
 
Tom Phillips 6/3/2018 12:43 PM
Quote Originally Posted by tyler8611 View Post
Thought so. I'll replace that particular power cap and check the grounding joints.
Don't jump straight to "replace." Troubleshoot first including connections & grounding. In this case just clip a new cap across the one in the circuit. If that makes no difference then the existing cap is not the problem.
 
tyler8611 6/3/2018 12:47 PM
Quote Originally Posted by Tom Phillips View Post
Don't jump straight to "replace." Troubleshoot first including connections & grounding. In this case just clip a new cap across the one in the circuit. If that makes no difference then the existing cap is not the problem.
Went straight to replace and the cap ended up not being the problem. I did have to touch up the heater pins on this socket earlier. I guess I should be checking every connection.
 
tyler8611 6/3/2018 1:56 PM
Went though and resoldered all the associated pins. Still motorboating from the reverb recovery. I traced the problem to V4. Tries Tried multiple tubes, changed all caps, same result.
 
tyler8611 6/4/2018 6:48 AM
I'm not actually sure if it's motorboating per se, but its definitely a loud low rumble. Never experienced before.
 
tyler8611 6/4/2018 7:05 AM
I wonder now whether the problem relates to the grounding of the 2nd filter cap. I tied it along with the PI and preamp filter caps, with a wire connecting to the copper bus. Perhaps I should have grounded it with the first stage at the PT bolt with the center tap.
 
Randall 6/4/2018 12:21 PM
I just built a DR, I connected C and D to a copper preamp ground bus, and the first three caps to chassis next to the PT. Mine is as quiet as a mouse.
 
tyler8611 6/4/2018 12:58 PM
Quote Originally Posted by Randall View Post
I just built a DR, I connected C and D to a copper preamp ground bus, and the first three caps to chassis next to the PT. Mine is as quiet as a mouse.
I'll certainly have to try it. And I need to verify the pots are working correctly. I've tried about everything else.
 
tyler8611 6/4/2018 4:48 PM
Quote Originally Posted by tyler8611 View Post
I'll certainly have to try it. And I need to verify the pots are working correctly. I've tried about everything else.
Tried it- no difference. Resoldered everything. V4 had 170v and 160v on the plates. Reverb red center tap: 395v. Cathode 1.3. Only thing I havent checked is the heater wiring from that tube. Touched up the joints but the pair could be shorted.
 
tyler8611 6/5/2018 2:57 PM
Quote Originally Posted by Randall View Post
I just built a DR, I connected C and D to a copper preamp ground bus, and the first three caps to chassis next to the PT. Mine is as quiet as a mouse.
Where did you ground the copper bus? Mine is near the input. It turns out I already had the grounds wired the way you're describing. First two stages to the center tap ground, others to the buss. So unless the opposite may be true for my amp, I have no idea what's causing this.
 
pdf64 6/6/2018 9:51 AM
It may be helpful to record a clip of the motorboating issue, along with the effect adjusting any controls may have on it. Upload to youtube etc and provide a link.
 
tyler8611 6/6/2018 10:21 AM
Quote Originally Posted by pdf64 View Post
It may be helpful to record a clip of the motorboating issue, along with the effect adjusting any controls may have on it. Upload to youtube etc and provide a link.
Good idea.
 
tyler8611 6/6/2018 10:24 AM
I thought I'd had it traced down to the fact that my V4 to V5 heater pair was out of phase, but correcting that didn't cure it. All I have left to try is the V3 to V4 pair, which checks out good on continuity.
 
pdf64 6/6/2018 10:48 AM
With a balanced heater system, there a tiny theoretical benefit from arranging p-p power tube heaters in like polarity, but for the rest of the amp, I think it's immaterial; rather the guideline of lining up heater polarity for all the sockets seems akin to a good luck charm that everyone clings to because they don't want their amp to hum
As there's a global NFB loop, the LTP phase splitter is really part of the power amp.
To help get your head around HT - 0V hum considerations, see The Valve Wizard
BF 0V arrangements are kinda random really, the fact that generally it works well may have been down to trial and error and good luck; hence it may be a good idea to review where your amp's 0V arrangement differs from a real BF.
 
tyler8611 6/6/2018 11:34 AM
Quote Originally Posted by pdf64 View Post
With a balanced heater system, there a tiny theoretical benefit from arranging p-p power tube heaters in like polarity, but for the rest of the amp, I think it's immaterial; rather the guideline of lining up heater polarity for all the sockets seems akin to a good luck charm that everyone clings to because they don't want their amp to hum
As there's a global NFB loop, the LTP phase splitter is really part of the power amp.
To help get your head around HT - 0V hum considerations, see The Valve Wizard
BF 0V arrangements are kinda random really, the fact that generally it works well may have been down to trial and error and good luck; hence it may be a good idea to review where your amp's 0V arrangement differs from a real BF.
Thanks I'll look into this.
 
g1 6/6/2018 12:13 PM
Quote Originally Posted by tyler8611 View Post
Pin 8: 15.9 mA (64.2 mV)
. 16.2 mA (65 mV)
Sorry to go back to the bias thing again, but these readings don't make sense. And the mV reading for a 1 ohm cathode resistor indicate a very hot bias that may explain why the pin5 voltage is so far from norm (-20V vs -35V)
Heavy loading of the supply could also account for other odd issues.

How are you doing the current measurement (mA) ? Are you disconnecting the cathode resistor to do it?
Are the cathode resistors actually 1 ohm and do you measure around 65mV across each at idle with no signal?
 
tyler8611 6/6/2018 12:21 PM
Quote Originally Posted by g1 View Post
Sorry to go back to the bias thing again, but these readings don't make sense. And the mV reading for a 1 ohm cathode resistor indicate a very hot bias that may explain why the pin5 voltage is so far from norm (-20V vs -35V)
Heavy loading of the supply could also account for other odd issues.

How are you doing the current measurement (mA) ? Are you disconnecting the cathode resistor to do it?
Are the cathode resistors actually 1 ohm and do you measure around 65mV across each at idle with no signal?
Yes I'm measuring at idle, no signal. Not disconnecting. They are definitely 1 ohm and soldered between pin 8 and grounding tabs. These are the readings I get. Meter set to lowest range on both mA and mV (200).
 
tyler8611 6/6/2018 12:31 PM
Just a reminder, the normal channel plays fine with V4 removed. The rumbling goes away. But no sound from vib channel at any setting.
 
tyler8611 6/6/2018 12:38 PM
Quote Originally Posted by g1 View Post
Sorry to go back to the bias thing again, but these readings don't make sense. And the mV reading for a 1 ohm cathode resistor indicate a very hot bias that may explain why the pin5 voltage is so far from norm (-20V vs -35V)
Heavy loading of the supply could also account for other odd issues.

How are you doing the current measurement (mA) ? Are you disconnecting the cathode resistor to do it?
Are the cathode resistors actually 1 ohm and do you measure around 65mV across each at idle with no signal?
What's the typical range for mV across the resistor?
 
tyler8611 6/6/2018 4:25 PM
I've recorded it but I don't know how to post it on here.
 
tyler8611 6/6/2018 4:59 PM
I had hooked it up to a different speaker that I could hear better. Definitely motorboating.
 
g1 6/6/2018 6:08 PM
You have to disconnect the cathode resistor if you want to measure mA current directly. Current measurement must be done with the meter in series. The point of having the 1 ohm cathode resistors is so you don't have to 'break in' to the circuit and can just measure voltage in mV across the resistor.
So your mA numbers are not valid. Your measurement of 65mV across the resistor is what you should go by. 65mV divided by 1 ohm equals 65mA idle current. At 400V plate, you are idling those tubes around 26watts. If you are lucky they may still be ok.
Somewhere around 20mA is probably more appropriate, which will measure as 20mV across the 1 ohm resistor.
 
tyler8611 6/6/2018 6:46 PM
Quote Originally Posted by g1 View Post
You have to disconnect the cathode resistor if you want to measure mA current directly. Current measurement must be done with the meter in series. The point of having the 1 ohm cathode resistors is so you don't have to 'break in' to the circuit and can just measure voltage in mV across the resistor.
So your mA numbers are not valid. Your measurement of 65mV across the resistor is what you should go by. 65mV divided by 1 ohm equals 65mA idle current. At 400V plate, you are idling those tubes around 26watts. If you are lucky they may still be ok.
Somewhere around 20mA is probably more appropriate, which will measure as 20mV across the 1 ohm resistor.
Plate is 411 and 409 and power tube bias is 15.9 and 16.4. Reading for mV is 66.6 and 64.5. I put the voltage and current numbers in the weber bias calculator and got 50% dissipation.

So this way of measuring across the 1 ohm is invalid and the resistor would have to be pulled from ground?
 
Leo_Gnardo 6/6/2018 7:00 PM
Quote Originally Posted by tyler8611 View Post
Plate is 411 and 409 and power tube bias is 15.9 and 16.4. Reading for mV is 66.6 and 64.5. I put the voltage and current numbers in the weber bias calculator and got 50% dissipation.

So this way of measuring across the 1 ohm is invalid and the resistor would have to be pulled from ground?
About the 1 ohm resistor, it's not an invalid method, it's an either-or situation. Either you trust the resistor to be reasonably close to 1.00 ohm and then 1 mV measured across the resistor indicates 1 mA of bias current. OR break the connection from output tube's cathode and connect one lead of your milliammeter to that cathode and the other to ground, then you'll read milliamps directly thru the meter.

Something's not right about the math also, 411V x .0666A = 27.4W, way in excess of a 6V6's 12W plate dissipation rating. We might expect that if the bias voltage on the control grid is -15.9V. Quite a lot less than the -35ish volts that's expected. Similar for the other 6V6. At that rate they should be glowing orange, ow!
 
tyler8611 6/6/2018 7:09 PM
Quote Originally Posted by Leo_Gnardo View Post
About the 1 ohm resistor, it's not an invalid method, it's an either-or situation. Either you trust the resistor to be reasonably close to 1.00 ohm and then 1 mV measured across the resistor indicates 1 mA of bias current. OR break the connection from output tube's cathode and connect one lead of your milliammeter to that cathode and the other to ground, then you'll read milliamps directly thru the meter.

Something's not right about the math also, 411V x .0666A = 27.4W, way in excess of a 6V6's 12W plate dissipation rating. We might expect that if the bias voltage on the control grid is -15.9V. Quite a lot less than the -35ish volts that's expected. Similar for the other 6V6. At that rate they should be glowing orange, ow!
I think that calculator subtracts the screen current from the bias number and then multiplies that by the plate volatage. That's 6W, according to them.

One of them is glowing blue, but that's it.
 
g1 6/6/2018 8:10 PM
Quote Originally Posted by tyler8611 View Post
So this way of measuring across the 1 ohm is invalid and the resistor would have to be pulled from ground?
Yes, if you want to use the current range of your meter (mA) you must remove the resistor or break a connection and install the meter in series. Right now, you are measuring the current in parallel with the 1 ohm resistor. Some current goes through it, and some goes through your meter. This gives you an incorrect mA reading.
If you want to leave the 1 ohm resistor in circuit, you can only do voltage (mV) measurements with your meter.
Turn down the idle current till you have 20mV across the 1 ohm resistors. What is now the grid voltage at pin5 of the power tubes? What is the plate voltage at pin3?
Is it still motorboating?
 
Enzo 6/6/2018 8:18 PM
I don't worry about the 1 ohm diode accuracy. I think I bought 1% ones just for the form factor. But so what if they are off 5%? If we have say 30ma current, a 5% margin is just a milliamp and a half.
 
tyler8611 6/6/2018 8:55 PM
Quote Originally Posted by g1 View Post
Yes, if you want to use the current range of your meter (mA) you must remove the resistor or break a connection and install the meter in series. Right now, you are measuring the current in parallel with the 1 ohm resistor. Some current goes through it, and some goes through your meter. This gives you an incorrect mA reading.
If you want to leave the 1 ohm resistor in circuit, you can only do voltage (mV) measurements with your meter.
Turn down the idle current till you have 20mV across the 1 ohm resistors. What is now the grid voltage at pin5 of the power tubes? What is the plate voltage at pin3?
Is it still motorboating?
Turned it down til I had 20mV. Pin 5 - 35v. Pin 3 on both is 458. Still motorboating from having V4 in.
 
g1 6/7/2018 12:16 PM
That sounds much better for idle current. You are now at about 9watts or 65% dissipation. You can see how much the heavy current had been pulling down the plate voltage. And you are at -35V at the grids just like the schematic (rather than the -20V you reported earlier).

Does the normal channel function properly with V4 pulled?
 
tyler8611 6/7/2018 2:39 PM
Quote Originally Posted by g1 View Post
That sounds much better for idle current. You are now at about 9watts or 65% dissipation. You can see how much the heavy current had been pulling down the plate voltage. And you are at -35V at the grids just like the schematic (rather than the -20V you reported earlier).

Does the normal channel function properly with V4 pulled?
Yes normal works fine with V4 pulled.

Vibrato channel- can only hear scratchy notes with volume at max. Vibrato does not kick in, even though the roach blinks, tube is good and voltages look normal.
 
g1 6/7/2018 5:46 PM
Ok. Motorboating and tremolo are not that far off from eachother.
Can you try disconnecting the wire that goes from the intensity pot to the .1uF/220K junction?
 
tyler8611 6/7/2018 6:34 PM
Quote Originally Posted by g1 View Post
Ok. Motorboating and tremolo are not that far off from eachother.
Can you try disconnecting the wire that goes from the intensity pot to the .1uF/220K junction?
Yes I'll try that. The yellow wire.
 
tyler8611 6/7/2018 8:42 PM
Quote Originally Posted by g1 View Post
Ok. Motorboating and tremolo are not that far off from eachother.
Can you try disconnecting the wire that goes from the intensity pot to the .1uF/220K junction?
Motorboating gone. Some hiss and a good amount of hum. Reverb permanently on.
 
tyler8611 6/7/2018 8:46 PM
Quote Originally Posted by g1 View Post
Ok. Motorboating and tremolo are not that far off from eachother.
Can you try disconnecting the wire that goes from the intensity pot to the .1uF/220K junction?
It was playing at full volume, like the normal channel.
 
g1 6/7/2018 9:19 PM
I'm not sure if you mean the reverb and volume pots are not working? Or everything is functional except no trem? (aside from hum and hiss issues)
 
tyler8611 6/8/2018 5:15 AM
Quote Originally Posted by g1 View Post
I'm not sure if you mean the reverb and volume pots are not working? Or everything is functional except no trem? (aside from hum and hiss issues)
Volume and tone are working. Trem isn't
Reverb is always in the signal in a very heavy amount. Neither turning rhe pot nor pushing the footswitch changes the reverb in an any way. It's always on, a lot of it.
 
g1 6/8/2018 1:39 PM
It would help if you could post some clear pictures of the board, pots, etc. so we can check the layout & wiring.
 
tyler8611 6/8/2018 2:25 PM
Quote Originally Posted by g1 View Post
It would help if you could post some clear pictures of the board, pots, etc. so we can check the layout & wiring.
Ok I'll do that asap.
 
tyler8611 6/8/2018 3:33 PM
Quote Originally Posted by g1 View Post
It would help if you could post some clear pictures of the board, pots, etc. so we can check the layout & wiring.
Ok I have 11 pics and a recording of the motorboating but I don't know how to post them on here. Any tips?
 
g1 6/8/2018 5:45 PM
When you have the reply box open, click on 'go advanced' (below the box). Then scroll down to 'manage attachments' and click on it. From there you should be able to add what you want.
 
tyler8611 6/8/2018 5:48 PM
Quote Originally Posted by g1 View Post
When you have the reply box open, click on 'go advanced' (below the box). Then scroll down to 'manage attachments' and click on it. From there you should be able to add what you want.
Thanks I'll see if it works.
 
tyler8611 6/8/2018 6:04 PM
Going to have to make my files smaller.
 
tyler8611 6/8/2018 10:37 PM
[ATTACH=CONFIG]49202[/ATTACH][ATTACH=CONFIG]49201[/ATTACH][ATTACH=CONFIG]49200[/ATTACH][ATTACH=CONFIG]49199[/ATTACH][ATTACH=CONFIG]49198[/ATTACH][ATTACH=CONFIG]49197[/ATTACH][ATTACH=CONFIG]49196[/ATTACH][ATTACH=CONFIG]49195[/ATTACH][ATTACH=CONFIG]49194[/ATTACH][ATTACH=CONFIG]49202[/ATTACH][ATTACH=CONFIG]49201[/ATTACH][ATTACH=CONFIG]49200[/ATTACH][ATTACH=CONFIG]49199[/ATTACH][ATTACH=CONFIG]49198[/ATTACH][ATTACH=CONFIG]49197[/ATTACH][ATTACH=CONFIG]49196[/ATTACH][ATTACH=CONFIG]49195[/ATTACH][ATTACH=CONFIG]49194[/ATTACH]
 
tyler8611 6/8/2018 10:47 PM
[ATTACH=CONFIG]49203[/ATTACH]
 
tyler8611 6/9/2018 6:38 AM
I have one more pic of the inside, showing the output components, tube sockets and PT- facing the back of the chassis. Wouldn't let me post for some reason. It's under 3mb. I'll keep trying.
 
tyler8611 6/9/2018 6:43 AM
[ATTACH=CONFIG]49207[/ATTACH]
 
tyler8611 6/9/2018 6:45 AM
That's all I took. Not the neatest work, obviously and I can't believe I forgot to put the twisted pair from the vib channel input grid through the proper hole. But I can always fix it later.
 
tyler8611 6/9/2018 6:52 AM
V4 Motorboating clip
[ATTACH]49208[/ATTACH]
 
g1 6/9/2018 11:33 AM
That big orange drop cap connected to the tremolo bug, what value is it? (and why?).
Does it make any difference it it is removed or disconnected at one end?
 
tyler8611 6/9/2018 11:36 AM
Quote Originally Posted by g1 View Post
That big orange drop cap connected to the tremolo bug, what value is it? (and why?).
Does it make any difference it it is removed or disconnected at one end?
That's a .022 to ground. Supposed to prevent ticking. Makes no difference at all otherwise.
 
g1 6/9/2018 11:44 AM
Ok. It looked bigger to me. I thought maybe it was a .1uF. So you tried with it lifted and no difference?
And you did say that you could see the bulb flashing?
 
tyler8611 6/9/2018 11:46 AM
Quote Originally Posted by g1 View Post
Ok. It looked bigger to me. I thought maybe it was a .1uF. So you tried with it lifted and no difference?
And you did say that you could see the bulb flashing?
Didn't try it lifted yet but I will now. I just put it in after reading about it as a tip.
 
tyler8611 6/9/2018 11:47 AM
Quote Originally Posted by tyler8611 View Post
Didn't try it lifted yet but I will now. I just put it in after reading about it as a tip.
Yes can see the bulb flashing.
 
Tom Phillips 6/9/2018 1:02 PM
tyler8611,
You posted really nice high resolution photos. Would you please include at lease one photo that shows the whole gut shot as a single view?
Cheers,
Tom
 
tyler8611 6/9/2018 1:33 PM
Quote Originally Posted by Tom Phillips View Post
tyler8611,
You posted really nice high resolution photos. Would you please include at lease one photo that shows the whole gut shot as a single view?
Cheers,
Tom
Sure, no problem.
 
tyler8611 6/9/2018 1:41 PM
Quote Originally Posted by tyler8611 View Post
Sure, no problem.
[ATTACH=CONFIG]49210[/ATTACH]


Had to crop it to get it under 3mb.
 
galaxiex 6/9/2018 3:03 PM
Quote Originally Posted by tyler8611 View Post
[ATTACH=CONFIG]49210[/ATTACH]


Had to crop it to get it under 3mb.
Just a FYI....

I use BUZZ 3D Media converter to convert images and reduce file size.
It works great but you are limited to 1280X1024 PNG or JPEG output.
Not really a problem as far as size goes, still decent.
It's an older program... there may be better/newer ones out there.
Oh ya, it freeware.

http://www.tucows.com/preview/510875
 
shortcircuit 6/9/2018 5:09 PM
Here's a stacked image of a working 65 deluxe reverb (bottom photo) , compared to your build , hope it helps , g1 in#117 asked my first question, orange drop (is that the new LIKE)[ATTACH=CONFIG]49222[/ATTACH][ATTACH=CONFIG]49223[/ATTACH]
 
dstrat 6/9/2018 5:32 PM
disregard
 
tyler8611 6/10/2018 1:15 AM
Quote Originally Posted by shortcircuit View Post
Here's a stacked image of a working 65 deluxe reverb (bottom photo) , compared to your build , hope it helps , g1 in#117 asked my first question, orange drop (is that the new LIKE)[ATTACH=CONFIG]49213[/ATTACH]
Thanks for that comparison. The orange drops are mostly PS series in there right now. Just one or two 715p.
 
tyler8611 6/10/2018 11:46 AM
Touched up the pots and grounds and eliminated the cap on the roach. Going to see if it makes ant difference.
 
tyler8611 6/10/2018 2:18 PM
Well guys, it's fixed! The last few things I did were touch up the pots and grounds, and I removed the .022 cap from the trem roach, which may well could have been the cause. I appreciate you all giving advice along the way!

Got it biased at 20mV with 444 plate voltage. Sounds excellent.
 
tyler8611 6/11/2018 7:21 AM
Now I need to find the cause of this ratty distortion that's like a tearing sound that I get when vibrato channel is on 10. It's not the speaker and not V1 or V2. Maybe one of the other preamp tubes. I already swapped JJ 6v6s and it made no difference. Aside from that, the amp is running just fine and sounds really good!
 
SoulFetish 6/11/2018 10:38 PM
Quote Originally Posted by tyler8611 View Post
Didn't try it lifted yet but I will now. I just put it in after reading about it as a tip.
Yes, this is a common technique for reliably removing any audible tick. Although, I always implement it in a slightly different way than you did. I bypass the 10M resistor with a .047ĩF cap. The reason I do it this way is that I have an large surplus of little white with box caps with leads just long enough to bypass the resistor. Since the power supply and ground are at the same potential for AC, it's six in one – half dozen in the other.
The important thing to remember when making this alteration is this: In order to maximize the mojo, use an inexpensive and reliable economy cap for this.
[ATTACH=CONFIG]49253[/ATTACH]
 
tyler8611 6/12/2018 4:35 PM
Quote Originally Posted by SoulFetish View Post
Yes, this is a common technique for reliably removing any audible tick. Although, I always implement it in a slightly different way than you did. I bypass the 10M resistor with a .047ĩF cap. The reason I do it this way is that I have an large surplus of little white with box caps with leads just long enough to bypass the resistor. Since the power supply and ground are at the same potential for AC, it's six in one – half dozen in the other.
The important thing to remember when making this alteration is this: In order to maximize the mojo, use an inexpensive and reliable economy cap for this.
[ATTACH=CONFIG]49253[/ATTACH]
Wow cool mod. Makes sense. I'll definitely give it a try.
 
tyler8611 6/12/2018 6:27 PM
Quote Originally Posted by g1 View Post
You have to disconnect the cathode resistor if you want to measure mA current directly. Current measurement must be done with the meter in series. The point of having the 1 ohm cathode resistors is so you don't have to 'break in' to the circuit and can just measure voltage in mV across the resistor.
So your mA numbers are not valid. Your measurement of 65mV across the resistor is what you should go by. 65mV divided by 1 ohm equals 65mA idle current. At 400V plate, you are idling those tubes around 26watts. If you are lucky they may still be ok.
Somewhere around 20mA is probably more appropriate, which will measure as 20mV across the 1 ohm resistor.
Is 20 mA (mV) good with 451 on the plates?
 
g1 6/12/2018 6:33 PM
Yes, that should be fine.
(edit) That's about 9W idle which is about 70% of the 12W that 6V6 are rated at.
(65% of the 14W a JJ 6V6 is rated at)
 
SoulFetish 6/12/2018 6:37 PM
Quote Originally Posted by tyler8611 View Post
Is 20 mA (mV) good with 451 on the plates?
If you have 20mA of cathode current, figure about 2mA of quiescent screen current and 18mA for your plate, you at 70% dissapation. Without drawing up a load line, i’d say your probably fine.
 
SoulFetish 6/12/2018 6:40 PM
I’ve seen 6V6s rated for both 12W and 14W. The 70% figure I quoted was at 12W.
 
g1 6/12/2018 6:50 PM
Quote Originally Posted by SoulFetish View Post
I’ve seen 6V6s rated for both 12W and 14W. The 70% figure I quoted was at 12W.
I think your 12W figure is correct. The 14W is for the newer JJ type which seems more of a 6V6/6L6 hybrid.
I've edited my previous post for the 12W version. If he's using JJ's, he can use the 9 over 14 = 65% figure.
 
tyler8611 6/13/2018 7:48 AM
Thanks for the help guys. The only issue I have now is this sound like speaker cone tearing (though it isn't) when I dime the vibrato channel. It is a ripping sound that spurts around after sustaining a chord. Happens with or without the effects. I've changed V2 and it's still there. Again, only happens on 10.

The 6v6s are almost new JJs. The one nearest the rectifier has a slight blue glow around one of the spacers and the blue actually intensifies when I play a note or chord on 10.

Guess it's either that power tube or something internal. I swapped preamp tubes and also hooked up to a different speaker with the same result.
 
pdf64 6/13/2018 8:01 AM
Quote Originally Posted by tyler8611 View Post
Thanks for the help guys. The only issue I have now is this sound like speaker cone tearing (though it isn't) when I dime the vibrato channel. It is a ripping sound that spurts around after sustaining a chord...
Issues that occur when gain is increased may be due to oscillation; closely examine the precise placement of wires in a real BF and review your lead dress against that.
 
tyler8611 6/13/2018 8:11 AM
Quote Originally Posted by pdf64 View Post
Issues that occur when gain is increased may be due to oscillation; closely examine the precise placement of wires in a real BF and review your lead dress against that.
Ah that may be it! I do need to go back and recheck the lead dress anyway. Thanks, I'll see what happens, maybe take some pics and report back.
 
tyler8611 6/13/2018 3:15 PM
I will note that, with the chassis out of the cab, it doesn't exhibit any tearing sound. I warmed the bias back up from 18 mA to 20, so it's either that or the cab that's causing it perhaps.
 
tyler8611 6/13/2018 3:27 PM
I did barely tuck the wires into proper place but not much. They were good already. Who knows. I have it back in the cab so we'll see.
 
tyler8611 6/13/2018 3:45 PM
The cab is causing it, apparently. That's when it returns.
 
tyler8611 6/13/2018 3:47 PM
[ATTACH]49299[/ATTACH]
 
g1 6/13/2018 6:22 PM
I can't really make out the bad noise from the soundfile, but I don't have much for speakers.
Often, a fault that shows up only in cabinet is due to vibration. Could be a bad tube, bad tube/socket connection, bad solder joint, dirty pot, etc.
I would try applying a constant signal with the chassis out of the cab, then tap around the chassis with a chopstick or rubber mallet or something and see if you can recreate the problem.
 
tyler8611 6/14/2018 7:44 AM
Quote Originally Posted by g1 View Post
I can't really make out the bad noise from the soundfile, but I don't have much for speakers.
Often, a fault that shows up only in cabinet is due to vibration. Could be a bad tube, bad tube/socket connection, bad solder joint, dirty pot, etc.
I would try applying a constant signal with the chassis out of the cab, then tap around the chassis with a chopstick or rubber mallet or something and see if you can recreate the problem.
Sorry, should have had my phone closer to the amp. It's a quick tearing sound distinguishable from the natural distortion. Happens during sustained chords. I found last night it begins to occur at about 8 on volume.

I'll go back in and do a more thorough check. I didn't observe anything odd when I poked around the lead dress previously. Would it more likely be caused by V2 or the 6v6s?
 
g1 6/14/2018 1:59 PM
It could be any tube. When it's doing it in the cab you can hold the tubes with a clean rag (don't burn your hand!) one at a time and see if you can make it stop. You can use a clean oven mitt too.
 
tyler8611 6/14/2018 2:23 PM
 
tyler8611 6/14/2018 2:26 PM
Quote Originally Posted by g1 View Post
It could be any tube. When it's doing it in the cab you can hold the tubes with a clean rag (don't burn your hand!) one at a time and see if you can make it stop. You can use a clean oven mitt too.
Playing with the chassis out of the cab, the rca 7025 i had in there was still causing it. Substituted a tung sol, which doesn't have the problem, at least not out of the chassis. We'll see what happens in the cab.
 
jmaf 6/14/2018 2:43 PM
Quote Originally Posted by tyler8611 View Post
Playing with the chassis out of the cab, the rca 7025 i had in there was still causing it.
Remember we're blind-helping you here. So if you tell us the problem does not happen out of the cab then you find that it does, you've thrown us off. First thing I'd tell you it's the tubes but if it didn't happen out of the cab then obviously not, glad you found that.

One other thing: if this is getting worse in the cab, means that when the tubes are upside down it gets worse, then there can be mechanical problem in the tubes.

Also tubes are microphonic, they can be obnoxious when in a cabinet, the speaker shakes the tubes which replicate the vibration in the output, this matches what you describe when you play a chord, the underlying vibration.
 
tyler8611 6/14/2018 2:47 PM
Quote Originally Posted by jmaf View Post
Remember we're blind-helping you here. So if you tell us the problem does not happen out of the cab then you find that it does, you've thrown us off. First thing I'd tell you it's the tubes but if it didn't happen out of the cab then obviously not, glad you found that.

One other thing: if this is getting worse in the cab, means that when the tubes are upside down it gets worse, then there can be mechanical problem in the tubes.

Also tubes are microphonic, they can be obnoxious when in a cabinet, the speaker shakes the tubes which replicate the vibration in the output, this matches what you describe when you play a chord, the underlying vibration.
Could it be a mechanical problem in any tube? Meaning all the ones having to do with V2?
 
jmaf 6/14/2018 3:10 PM
Quote Originally Posted by tyler8611 View Post
Could it be a mechanical problem in any tube? Meaning all the ones having to do with V2?
Don't know what you mean by having to do with V2?

What you describe, above volume 8 on sustained chords clearly sounds like feedback through the tubes, chassis vibration coming back through the tubes, etc. Could be a bunch of things.
 
tyler8611 6/14/2018 3:27 PM
Quote Originally Posted by jmaf View Post
Don't know what you mean by having to do with V2?

What you describe, above volume 8 on sustained chords clearly sounds like feedback through the tubes, chassis vibration coming back through the tubes, etc. Could be a bunch of things.
I'll be tube swapping shortly.
 
g1 6/14/2018 3:32 PM
Quote Originally Posted by jmaf View Post
Don't know what you mean by having to do with V2?
He's only getting the bad sound on the vibrato channel, so V2 or any other tubes that channel goes through, like V4, V6, and power tubes.
 
jmaf 6/14/2018 7:16 PM
Quote Originally Posted by g1 View Post
He's only getting the bad sound on the vibrato channel, so V2 or any other tubes that channel goes through, like V4, V6, and power tubes.
Oh, gotya. Thanks.

Once he swaps tubes I guess we'll get a better idea.
 
tyler8611 6/17/2018 10:41 AM
Hey just wanted to finally update, busy weekend. The problem was solved by a swap. It was either the tremolo tube or phase splitter, since I did those at the same time. No more harsh ripping!
 
Tone Meister 6/17/2018 8:02 PM
Quote Originally Posted by tyler8611 View Post
Hey just wanted to finally update, busy weekend. The problem was solved by a swap. It was either the tremolo tube or phase splitter, since I did those at the same time. No more harsh ripping!
Really? After all that you'd swap two tubes at a time and forego the opportunity to pinpoint the issue? I'd have to know, but that's just me. Glad you got it sorted out, but I'd have to KNOW.
 
Steve A. 6/17/2018 11:28 PM
Quote Originally Posted by Tone Meister View Post
Really? After all that you'd swap two tubes at a time and forego the opportunity to pinpoint the issue? I'd have to know, but that's just me. Glad you got it sorted out, but I'd have to KNOW.
Good point but my guess would be the phase inverter. After 157 posts (just here on MEF!) I certainly hope that all of the problems have been solved.

Steve A.
 
tyler8611 6/18/2018 5:28 AM
Quote Originally Posted by Tone Meister View Post
Really? After all that you'd swap two tubes at a time and forego the opportunity to pinpoint the issue? I'd have to know, but that's just me. Glad you got it sorted out, but I'd have to KNOW.
I can easily reinsert the previous tubes, recreate the problem and find out which was causing it, and I will. I was simply tired of doing one tube at a time and didn't think the trem tube would make a difference because several different tubes had already been in there while the problem was occurring. I had never changed the phase inverter until yesterday, mainly because it's a JAN blackplate. So I'm quite certain that was the one. But you never know.

I'll reinsert the old phase inverter and trem tube and find out for sure. Honestly I just felt like playing once I heard the ugly distortion had gone. Thanks guys!
 
tyler8611 6/18/2018 5:30 AM
Quote Originally Posted by Steve A. View Post
Good point but my guess would be the phase inverter. After 157 posts (just here on MEF!) I certainly hope that all of the problems have been solved.

Steve A.
I think so too, but I'll find out for certain and report back.
 
1ampman 6/18/2018 6:55 AM
Lack of high voltage is caused by open equalizing resistors under the circuit board under the dog house. You need to flip over the cap circuit board to get to them 220K 1W
 
Tone Meister 6/18/2018 3:36 PM
Quote Originally Posted by tyler8611 View Post
I can easily reinsert the previous tubes, recreate the problem and find out which was causing it, and I will. I was simply tired of doing one tube at a time and didn't think the trem tube would make a difference because several different tubes had already been in there while the problem was occurring. I had never changed the phase inverter until yesterday, mainly because it's a JAN blackplate. So I'm quite certain that was the one. But you never know.

I'll reinsert the old phase inverter and trem tube and find out for sure. Honestly I just felt like playing once I heard the ugly distortion had gone. Thanks guys!
Sorry if I came across like I was busting your chops because that wasn't my intention. But I had been watching this thread pretty closely and watched as each issue got sorted out and its root cause identified. I'm a novice, so I pay attention to these threads and learn what I can from them, which many times keeps me from having to start a thread of my own. For every thread I've started here on MEF, I have easily solved dozens more issues on my own by searching for previous instances of the same problem I was having.

This place is a cornucopia of in-depth technical knowledge. The best-of-the-best techs, designers, and engineers in the world unselfishly offer their assistance on this site, and I think we owe it to the next guy to clearly show the resolutions in our threads, including info on hard to find parts and non-conventional problem solving. In the end, it saves bandwidth and many times keeps the pros here from answering the same questions multiple times.

So yes, please do swap those tubes back in there (hope you know which one went where ) so you can put a lid on this one.
 
tyler8611 6/20/2018 7:56 AM
Quote Originally Posted by Tone Meister View Post
Sorry if I came across like I was busting your chops because that wasn't my intention. But I had been watching this thread pretty closely and watched as each issue got sorted out and its root cause identified. I'm a novice, so I pay attention to these threads and learn what I can from them, which many times keeps me from having to start a thread of my own. For every thread I've started here on MEF, I have easily solved dozens more issues on my own by searching for previous instances of the same problem I was having.

This place is a cornucopia of in-depth technical knowledge. The best-of-the-best techs, designers, and engineers in the world unselfishly offer their assistance on this site, and I think we owe it to the next guy to clearly show the resolutions in our threads, including info on hard to find parts and non-conventional problem solving. In the end, it saves bandwidth and many times keeps the pros here from answering the same questions multiple times.

So yes, please do swap those tubes back in there (hope you know which one went where ) so you can put a lid on this one.
No problem at all! I'm very grateful to you guys for helping and keeping me on the right path so I could find the problem and solve it. I hope this can be helpful for anyone who experiences the same or similar issues.

I'm finally going to have time today to swap the tubes back in one at a time in order to find out for sure which was the problem and report back.

I've had maybe two or three hours to play it since I sorted the problem. Sounds really great. No noise problems or grounding issues. All settings work properly, the effects are flawless. I'll see if I can record a clip through my interface or phone.

Not sure if I posted pics of the tubes or transformers, but I'll go over that. PT is from Classictone. It's running 25-30v over schematic voltages. Maybe a mojotone would have produced a lower voltage but from the spec sheet, the classictone looked like it would. Choke and OT are mojotone.

V1: rca 7025
V2 : rca 7025
V3: jan philips 12at7
V4: rca 7025
V5: EHX 12ax7 (replaced tung sol)
V6: mullard ecc81(replaced jan 12at7)
V7 and V8: JJ 6v6
V9: JJ GZ34

Speaker is a Weber 12F150 25w, no dope.
 
tyler8611 6/20/2018 4:10 PM
Just did a swap and confirmed it was the previous phase inverter tube causing the bad distortion.