bigdrums925 2/24/2018 3:15 AM
Marantz 18 receiver needs help
The listen test is that both sides are distorted, and the right channel is weak.
Voltages to the power transistors are +/- 37V both channels.
Can anyone tell me how to upload & post the .pdf service manual to here already stored on my computer?
Or can I even do that in .pdf?
Here are the schematics:
[ATTACH]47287[/ATTACH]
The service manual is available at hifiengine as well as the service bulletin.


There was a post below this one that had a correct copy of the service manual but that post has since disappeared
 
Pedro Vecino 2/24/2018 5:13 AM
Is this? [url]http://akdatabase.org/AKview/albums/userpics/10004/Marantz%20Model%2018%20Service%20Manual.pdf[/url]
 
bob p 2/24/2018 5:19 AM
Quote Originally Posted by bigdrums925 View Post
Can anyone tell me how to upload & post the .pdf service manual to here already stored on my computer?
Or can I even do that in .pdf?
You can upload a PDF to the board as if you were positing a photograph. Click on the link above that looks like a framed photograph, follow the directions. You will probably need to have javascript running on your browser for things to work.

[IMG]http://music-electronics-forum.com/attachment.php?attachmentid=47286&d=1519474950[/IMG]
 
olddawg 2/24/2018 12:12 PM
Before you do anything clean the tape monitor switches.
 
bigdrums925 2/24/2018 10:37 PM
starting with the P/S I found a diode CR5 pn 35-1015 (Marantz number) bad
one end tied to C11 the 10uf 575v cap, the other end ties the red/grn secondary.
Can anyone hazard a guess at what the CR5 ratings need to be, better yet a common diode number as I have quite a few?
All the list says is its a rectifier diode. Would a 1N2070 work?
C11 & CR5 are only shown on pg 1 of the schematics posted in my opening post above
 
Jazz P Bass 2/25/2018 9:43 AM
It looks as if CR5 diode is for that goofy front panel meter (o scope).

That should have nothing to do with the amp sounding bad.

1N2070 is only a 400 volt part.
I would not use it.
 
bigdrums925 2/25/2018 11:48 PM
I found a parts request page on the Marantz pages so I see if they can enlighten me or provide the proper diode.
Funny that the o-scope seemed to be working properly though with the open diode.
Thanks for the response Jazz P Bass
I have now cleaned the tape switches and pots/switches, thanks olddawg
 
Jazz P Bass 2/26/2018 12:07 AM
1N4007 would work fine.
 
bigdrums925 2/27/2018 2:10 AM
I put in a 1N4005 which seems to be working ok
Tracing the distorted signals back to the point where they are no longer distorted, I find myself at the tone amp board
Shown on pg 8 of the schematics, I find -36 v is at -42 v. The 12 v supply is 14 v but past 15k resistor R804,
the +1 v on the schematic is really - 4.4 v
R804 does measure 15k so what else could make the +1v be negative?
 
bigdrums925 3/1/2018 4:26 PM
Anyone?
 
nickb 3/1/2018 5:18 PM
What's the voltage on the base of Q803?
 
bigdrums925 3/1/2018 8:02 PM
This project has been sitting for a few days but:

This time the -4.4 v past R804 measures +2.5

Base voltage on both Q803 & Q807 is about 1.1 v (where its supposed to be +.2)
Emitter on both is about 3.3 v (where it's supposed to be +.8)
Collector on both is about -30.5 v (where its supposed to be - 27)

Pic of the output on the tone board:
[ATTACH=CONFIG]47375[/ATTACH]

What does the scope pattern tell me?
I can see the negative swing is badly clipped but why?
The same pattern is shown on the other channel as well.
 
nickb 3/2/2018 1:36 AM
Don't worry about the off voltages in sheet 8. I see that the voltage depends critically of the gain of the two transistors as it relies on the bias current thru R810. What you have there is not unexpected.

We need to know the vertical scale in order to really interpret the scope shot - you might simply be giving t too big a signal. Since you have a scope probe the collector of Q802 and the base of Q801.
 
bigdrums925 3/2/2018 2:54 AM
The signal going into the aux inputs is 2v P-P and about 1.5v coming into the tone board
collector of Q802 shows an undistorted sine wave of 25v P-P
base of Q801 shows and undistorted sine wave of 1.5v P-P
I did roll off the gain just a bit and all tone controls are at center
But the vertical scale is 5v per division in sheet 11
Output negative swing distortion of the tone board is the same, just a little smaller gain on the scope now
 
nickb 3/2/2018 3:05 AM
Quote Originally Posted by bigdrums925 View Post
The signal going into the aux inputs is 2v P-P and about 1.5v coming into the tone board
collector of Q802 shows an undistorted sine wave of 25v P-P
base of Q801 shows and undistorted sine wave of 1.5v P-P
I did roll off the gain just a bit and all tone controls are at center
But the vertical scale is 5v per division in sheet 11
Output negative swing distortion of the tone board is the same, just a little smaller gain on the scope now
You are driving it with about 10x the signal you should be. That is why it's clipped.
 
bigdrums925 3/2/2018 3:42 AM
OK you are right, but why would it not clip on the positive swing also?

This eliminated the distortion on the amp board but not at the speaker outputs.
I'll try for that tomorrow, Thank you
 
nickb 3/2/2018 5:33 AM
It's not biased at the midpoint of the swing as it doesn't need to be.

With the smaller signal scope the output and the input to the power amp.
 
bigdrums925 3/2/2018 5:45 PM
Signal going into the amp from the driver board is normal on 10K, 10J, & 10G and about equal signal strength
Output at speaker jacks is normal until turned up past 1/2 way
then it looks like this:
[ATTACH=CONFIG]47382[/ATTACH]
Taken on the 1 v per division scale
What do you make of it?
 
olddawg 3/2/2018 8:39 PM
Quote Originally Posted by bigdrums925 View Post
Signal going into the amp from the driver board is normal on 10K, 10J, & 10G and about equal signal strength
Output at speaker jacks is normal until turned up past 1/2 way
then it looks like this:
[ATTACH=CONFIG]47382[/ATTACH]
Taken on the 1 v per division scale
What do you make of it?
Do you have any dc offset on the output terminals. If there is no dc offset, what does it sound like through speakers with program music? You may have it fixed and chasing your tail.
 
bigdrums925 3/2/2018 10:32 PM
About 1 mV DC offset, music thru sounds terrible and no gain after about 1/3 on volume
Pic of sine wave thru with speaker connected (load)
[ATTACH=CONFIG]47383[/ATTACH]
Also at 1v per division
Nope, not fixed. Doesn't even sound good at low volume
 
olddawg 3/2/2018 11:23 PM
Quote Originally Posted by bigdrums925 View Post
About 1 mV DC offset, music thru sounds terrible and no gain after about 1/3 on volume
Pic of sine wave thru with speaker connected (load)
[ATTACH=CONFIG]47383[/ATTACH]
Also at 1v per division
Nope, not fixed. Doesn't even sound good at low volume
The simple fact that both channels are distorted usually indicates a power supply problem since it’s common to both channels. I would go back to the power supply section and check all of the supplies. Make sure they are within reason, symmetrical, and have no ripple. Check any and all current limiting resistors. Use a multimeter to start.
 
nickb 3/3/2018 1:41 AM
^^ Def check this things that olddawg mentioned. If you remove the load completely what does the output look like?

Edit: Ah I see you already did that.
 
bigdrums925 3/4/2018 2:23 AM
Difficult to say for certain that all the voltages are there cause it's point to point wiring in the PS, But I think they are.
The ripple seems ok except on the terminal strip:
[ATTACH=CONFIG]47393[/ATTACH]
the voltages are ~220v and `-72v where the scope shots that follow were taken:
[ATTACH=CONFIG]47394[/ATTACH]
[ATTACH=CONFIG]47395[/ATTACH]
the rest of the power supply points show a flat line on the scope so I don't know what these are

the left speaker output
[ATTACH=CONFIG]47396[/ATTACH]
right speaker output:
[ATTACH=CONFIG]47397[/ATTACH]
 
nickb 3/4/2018 2:43 AM
All the scope shots are almost meaningless without knowing the vertical scale and the horizontal scale. On one the vertical scale is far to sensitive as the signal if off the edges of the screen.

Just get you DMM out and measure the volts on the emitters of Q11, Q12, Q13 and Q14, the associated resistors might be an easier test point. If any of those are significantly different from 36V then measure on the other side of the associated resistors.
 
olddawg 3/4/2018 1:01 PM
If you have a clean signal from the line out.. check your power supply voltages where they enter the output amp section. If something is off follow it back. I would recommend using a Multimeter or DVM if you are not totally familiar with using a scope for accurate AC/DC measurements.
 
bigdrums925 3/4/2018 6:56 PM
The voltage on the output devices are all closely matched at +/- 37.5 v
going back to my previous question regarding ripple, all the filtered PS voltages show a flat line on the scope
except the 2 in the post above and the 2 pics. Any one understand why I would see a static pattern on those 2 points on the terminal strip shown in pic 1?
 
nickb 3/5/2018 12:58 AM
You cannot interpret the scope shots without knowing (1) The Vertical scale (2) Where you are probing on the schematic. Sometimes the horizontal scale is needed too. "Terminal Strip" means nothing - i have no idea where that is on the schematic.

Remove Q11, Q12, Q13 and Q14 and test them. https://vetco.net/blog/test-a-transi...04-12-25-37-07
 
J M Fahey 3/5/2018 1:44 AM
Not really getting into this, sorry but very short of time, but one point which scratches me the wrong way is that each power amp is split into TWO boards, a "driver" one (11-1002) with the differential pair front end (Q1003/1005) up to Vas (the main voltage gain stage which generates the rail to rail swing) Q1006, its active load Q1002 and "to make things interesting" Q1002 which in most amps receives just some fixed bias (1 to 2V) here it is turned into a "current mirror" by getting out of plase current fed to its base, courtesy of Q1004, which is fed out of phase signal (out of phase relative to what Q1006 receives) courtesy of Q1003 .

This drive board generates the main rail to rail swing which is then current amplified by the "current gain transistors"
Left Positive : Q8/12
Left negative: Q7/11
Right Positive: Q9/13
Right Negative: Q10/14

To boot, driver and output blocks are NOT shown side to side, to further obscure a circuit which already suffers from overcomplication.
I would redraw driver and current halves on a single sheet and the usual way , so the standard power amp which is hidden in there is recognizable.

You show distorted output waveforms, one of them unsymmetrical, (**please always** state each peak to peak value, don´t make us count screen divisions and wonder where the multiplier switch is set), which worsen a lot when trying to drive a load, so I suspect:

* the driver board.
Check all transistors get supply voltage (they should, but check anyway) but mainly remember that:
a) all NPN transistors have Base some 0.6V more positive then Emitter. Never negative or, say, 5V away from Emitter.
b) all NPN transistors have Collector more positive than emitter, always.
c) all PNP transistors do exactly the same as a and b but with the opposite polarity.
* Only transistors where it is normal to have zero or very low (a few mV) voltage BE or CE are the short protection ones Q3/4/5/6 because, well, they *should* not be activated until you have a real short in process.

You should get full rail to rail swing (minus a couple Volt losses) on Q1006 collector and on Q1002, both are the same thing just separated by 2.8V bias.
There are two driver boards, both apparently share same part numbers. The more confusion the merrier, huh?
If the driver board can´t swing, the output pairs won´t either, as they have no voltage gain, are basically high current buffers.

* the output/current żboard? (is it on PCB or wired PTP? )
* IF one driver fails, coupled power transistor won´t drive a load because it missed "push" from the driver.
* IF the power transistor blew open , or blew shorted but killed its emitter resistor in the process, the driver transistor can swing unloaded but lacks muscle to drive a speaker load. Might still drive phones though, which is confusing.

Ok, back to sleep, it´s 4AM here.

Good luck hunting.
 
bigdrums925 3/6/2018 8:30 AM
Looking for the +/- 1.4v being feed from the driver boards I find only pin 10G on left channel is delivering.
Pin 10K on both boards not working and pin 10G on right channel not working. Each of those 3 read 0.0v
So check Q1002 & Q1003?

* the output/current żboard? (is it on PCB or wired PTP? ) Its PTP
 
bigdrums925 3/6/2018 10:52 PM
* the driver board.
Check all transistors get supply voltage (they should, but check anyway) but mainly remember that:
a) all NPN transistors have Base some 0.6V more positive then Emitter. Never negative or, say, 5V away from Emitter.
b) all NPN transistors have Collector more positive than emitter, always.


Look at the schematic of the driver board 11-1002, Q1001
As you pointed out base is .6v more positive than emitter. readings I got E 31.8v B 32.8v C 1.2v
The schematic and my measurements are not in agreement with "all NPN transistors have Collector more positive than emitter, always"
Am I misunderstanding your statement?
 
Jazz P Bass 3/7/2018 7:08 AM
Q1001 is an NPN type transistor.

Q1002 is a PNP type.
Your voltage readings, if for Q1002, are good.
 
bigdrums925 3/9/2018 4:13 PM
This repair is a nightmare. Take a look at the driver board schematic. Q1001, Q1003, & Q1005 on the chart are all listed as Marantz # 34-1007.
Yet the schematic shows them as PNP & NPN devices.
One of the driver boards has had these 3 transistors replaced with ECG 234's. PNP's

Marantz has apparently long lost the lists that would tell us what Marantz part number equivalents are, and seemingly their authorized service centers have too.
So I'm not sure if this unit can ever be repaired since no one seems to know what the generic part numbers are or can provide the Marantz numbered parts.
Any one care to offer a suggestion how to solve this screwy mess?
 
nickb 3/9/2018 4:58 PM
Quote Originally Posted by bigdrums925 View Post
This repair is a nightmare. Take a look at the driver board schematic. Q1001, Q1003, & Q1005 on the chart are all listed as Marantz # 34-1007.
Yet the schematic shows them as PNP & NPN devices.
One of the driver boards has had these 3 transistors replaced with ECG 234's. PNP's

Marantz has apparently long lost the lists that would tell us what Marantz part number equivalents are, and seemingly their authorized service centers have too.
So I'm not sure if this unit can ever be repaired since no one seems to know what the generic part numbers are or can provide the Marantz numbered parts.
Any one care to offer a suggestion how to solve this screwy mess?
1) Do what Juan said "I would redraw driver and current halves on a single sheet and the usual way , so the standard power amp which is hidden in there is recognizable."
2) Measure the DCV on each transistor, annotate the schematic you you drew with this info and then post it.

BTW, If I wasn't getting getting +/-1.4V from the driver I'd be looking at the output stage not the driver.
 
bigdrums925 3/9/2018 9:26 PM
I will do my best to redraw the driver & output stage together but have no experience doing that so may take some time.

So are you saying that the output stage provides the +/- 1.4v?
I unsoldered that wire and found no voltage coming from the output or the driver board.
Something is very screwy here!
 
nickb 3/10/2018 1:12 AM
Quote Originally Posted by bigdrums925 View Post
I will do my best to redraw the driver & output stage together but have no experience doing that so may take some time.

So are you saying that the output stage provides the +/- 1.4v?
I unsoldered that wire and found no voltage coming from the output or the driver board.
Something is very screwy here!
I did not know you unsoldered the wire.

The signal comes from the driver board ( actually the voltage amplifier) but the voltage is determined by the base-emitter junction of the the driver transistor (e.g. Q7) and the emitter diode drop (e.g) CR19. If are getting zero drop on one of those that would tell us something is amiss there. If you unsoldered the wire then that changes things as we can no longer be sure what is happening.

Reconnect and measure as requested please.

EDIT: I'll draw up something for you.
 
nickb 3/10/2018 9:43 AM
Here is a first pass of it drawn in a more logical fashion. Still needs the component refs to be added.

[ATTACH]47500[/ATTACH]


EDIT: ..and now with some errors fixed and component refs. The two driver boards are the same so I didn't put all the refs on the second channel. Added some currents and expected voltages.

[ATTACH]47510[/ATTACH]
 
bigdrums925 3/10/2018 7:41 PM
WOW nickb that was quick. You must have a program for drawing electrical circuits, no?
I'll look this over and get you the voltages (as many as I can anyway) and post.
Gonna take a little time as I have obligations tonight and tomorrow.
And Thank You!
 
nickb 3/11/2018 1:19 AM
Yes, I use KiCad as it's free and very good. If you download it I can send you the project and then you can edit it yourself.

I've made some more corrections and fixed the bit about the 1.4V - I forgot abut the triple diodes in the bias cct.
 
bigdrums925 3/11/2018 3:45 AM
Yes go ahead and send me the latest drawing for KiCad.
Downloading it now
 
nickb 3/11/2018 5:55 AM
Here is the zip: [ATTACH]47512[/ATTACH]
 
bigdrums925 3/13/2018 12:52 PM
While checking for the requested voltages I found the output transistors on the left channel are both shorted.
I may have caused this because the emitter resistor on one of them burnt suddenly, but he other did not.
They have been replaced before and are Motorola MJ21193/MJ21194.
Is there other TO3's that might work in the mene time?
I will order new ones and should have them by 3/19/18
Will post the updated schematic with the measured voltages soon
 
bigdrums925 3/13/2018 5:05 PM
I have amended the KiCad schematic to show the voltages at the different transistors
I have saved it as "save current sheet only" but I don't see a updated file in that directory.
Should I save it as "save schematic project"?
How can I save it as "Model 18-6?"
 
bigdrums925 3/13/2018 5:19 PM
So this is my first attempt at amending a schematic in KiCad
See if it works
[ATTACH]47572[/ATTACH]
 
nickb 3/13/2018 5:26 PM
Jut print it as a pdf of chose the name at that point. You don't change the name of the project.
 
nickb 3/13/2018 5:43 PM
Quote Originally Posted by bigdrums925 View Post
So this is my first attempt at amending a schematic in KiCad
See if it works
[ATTACH]47572[/ATTACH]
Please just post the pdf so everyone can read it.

You have conflicting voltages i.e. on several nodes you have two different voltages. Have you at any time adjusted R26 i.e. the bias voltage setting trimmer?
 
bigdrums925 3/13/2018 6:30 PM
[ATTACH]47573[/ATTACH]

I will re examine the voltages and correct
never have adjusted any trim ports on this unit
 
bigdrums925 3/13/2018 6:33 PM
checking the .pdf I can see it does not show the amendments I made
So what do I need to do to have the .pdf reflect the changes?
Also: can you tell me how to delete or edit or select a value I've added to the schematic?

I have the service manual for this unit but believe it's too big to upload- I'll try again as it contains more accurate drawings
Nope it says failed to upload
 
bigdrums925 3/14/2018 3:59 PM
Tried downloading a pdf printer to file program which hasn't worked to allow me to post a pdf version of the KiCad .sch file I added the voltages to.
Don't know what to do at this point.
Filling in the voltages reveled an area around Q1, Q3, Q4 with many 0.0 v. Obviously something wrong there
I will try checking Q3, Q4 but Marantz part numbers and no help from them so I don't know what to do if they are bad....
 
Jazz P Bass 3/14/2018 4:06 PM
Try "Cute Pdf Writer".

CutePDF :: Product :: CutePDF Writer
 
bigdrums925 3/14/2018 4:26 PM
OK so took Q3 & Q4 out and tested. Q4 is good but Q3 is bad. Marantz part # 34-1013.
How can I find a replacement since this is a proprietary # and Marantz is no help at all?

I got Cute PDF and here is the result:

Upload failed
Damn!
 
nickb 3/14/2018 4:34 PM
Quote Originally Posted by bigdrums925 View Post
Tried downloading a pdf printer to file program which hasn't worked to allow me to post a pdf version of the KiCad .sch file I added the voltages to.
Don't know what to do at this point.
Filling in the voltages reveled an area around Q1, Q3, Q4 with many 0.0 v. Obviously something wrong there
I will try checking Q3, Q4 but Marantz part numbers and no help from them so I don't know what to do if they are bad....
As Jazz says Cute PDf will work. If you are on a recent Windows 7 or 10 it comes with a pdf printer "Microsoft Print to PDF"

See https://answers.microsoft.com/en-us/...3-92345d6e25df
 
The Dude 3/14/2018 4:36 PM
Quote Originally Posted by bigdrums925 View Post
OK so took Q3 & Q4 out and tested. Q4 is good but Q3 is bad. Marantz part # 34-1013.
How can I find a replacement since this is a proprietary # and Marantz is no help at all?
Is there not a generic number on the device itself?
 
bigdrums925 3/14/2018 4:42 PM
No printing on the transistor is same as schematic 34-1013
716 follows that Marantz # however
 
nickb 3/14/2018 4:42 PM
Quote Originally Posted by bigdrums925 View Post
OK so took Q3 & Q4 out and tested. Q4 is good but Q3 is bad. Marantz part # 34-1013.
How can I find a replacement since this is a proprietary # and Marantz is no help at all?
Just about any small signal PNP transistor will work there. It dissipates almost no power and has negligible voltage across it. It doesn't even need much gain. Have a look in your spares box and see what you can find. You can even run without it temporarily as it's just part of the current limit.

PS: Just make sure you get the pinout right
 
bigdrums925 3/16/2018 2:08 AM
CutePDF allows me to print to a file but the file will not open because it is unrecognizable or damaged says the error message
Microsoft Print to PDF is not available on my windows 7.
all I can do is post the .sch file and maybe someone can convert to pdf.
Nope cant do that either- not a valid file type
 
nickb 3/16/2018 2:16 AM
Quote Originally Posted by bigdrums925 View Post
CutePDF allows me to print to a file but the file will not open because it is unrecognizable or damaged says the error message
Microsoft Print to PDF is not available on my windows 7.
all I can do is post the .sch file and maybe someone can convert to pdf.
Nope cant do that either- not a valid file type
Consult the CUTEpdf online help. In the meantime just zip the sch and post it.
 
bigdrums925 3/17/2018 2:06 AM
[ATTACH]47628[/ATTACH]
 
nickb 3/17/2018 2:59 AM
PDF of post #56 [ATTACH]47629[/ATTACH]

I see everything around Q3 is still 0V, Have you removed/replaced it yet?
 
bigdrums925 3/17/2018 12:19 PM
Yes, there is now -1.3v on collector. 0v on emitter and base.
Waiting for output transistors I ordered
 
nickb 3/17/2018 2:13 PM
Well ,while you wait you can run it up with a signal generator with no load and see if you now get the full swing on the output using the scope. The driver transistors will provide enough current for small loads.
 
bigdrums925 3/17/2018 7:53 PM
I get about a 4v P-P swing at the driver collectors
The waveform looks much better but gets fuzzy & distorts as I turn up the tone controls
At least there's progress
 
nickb 3/18/2018 2:50 AM
Quote Originally Posted by bigdrums925 View Post
I get about a 4v P-P swing at the driver collectors
The waveform looks much better but gets fuzzy & distorts as I turn up the tone controls
At least there's progress
Did you mean "emitters"? If it really was the collectors of Q7 /Q8 that would be wrong.

You should probe the input the power amp to check for a sensibly sized ( no more than 4Vpp) undistorted signal followed by the output.

Now that you have Q3 removed please measure the voltages again, including the power rails, Now that we have a schematic there is no need to repost it. Just do a table of Q#, pin and it's voltage.
 
bigdrums925 3/18/2018 4:04 AM
Q3 was already replaced
I can measure all the voltages but would it not be easier to say that I now have a lovely set of equal sine waves on the sockets of the output transistors?
4v P-P on the bases Q11, Q12, and about 15v P-P on the collectors, 0v on the emitters no output transistors installed

Sorry if Im not following advice well. It's just that it will take some time before I can verify everything before reporting back and the nice undistorted waveforms on the sockets
of Q11 & Q12 seem to indicate this left channel should be working as soon as the transistors arrive

Correct me if I'm wrong about that
 
nickb 3/18/2018 4:19 AM
The problem was you reported the the swing on the driver collectors whereas I was expecting a measurement on the output. The driver collectors is not a place you would normally probe,

OK that sounds about right. There is load on the output due to C30 that is causing the drop across R34 and R29. That will go away once the output transistors are fitted. Turn R26 to maximum resistance before fitting the output transistors to avoid excessive quiescent current.

Time to look at the other channel?
 
bigdrums925 3/20/2018 11:42 PM
Moving to the right channel here are the measurements in dc volts:
base collector emitter
Q1001 28.5 1.5 29.9
Q1002 46.8 0 47.5
Q1003 .8 -39.7 1.6
Q1004 -38.8 1.8 -39.6
Q1005 .8 -38.9 1.5
Q1006 -38.9 -.2 -39.5
Q2 -.2 0 -.2
Q5 0 0 0
Q6 -.2 -.2 0
Q9 0 42.4 0
Q10 -.2 -42.5 -.2
Q13 42.4 0 43
Q14 -42.5 -.2 -42.7
 
nickb 3/21/2018 2:45 AM
Looks like Q6 and Q5 may be bad. Remove and retest.

BTW when working on SS amps I always bring the power up slowly with a variac and monitor the current to avoid blowing parts up. I'm not a fan of bulb limiters as they react too slowly to protect transistors in many cases. OTOH a bulb limiter is better than nothing.
 
bigdrums925 3/21/2018 7:58 PM
I replaced both Q5 & Q6 as they were bad.
But this did not provide for a sine wave on the collectors of Q13 & Q14 like it did for the other channel.
I removed Q10 and checked. Initially it tested ok but then tested bad.
I suspect both Q9 & Q10 are bad and need replacement.
Now, here's the problem. All I know about them is they are a NPN and a PNP device with Marantz numbers and that they are both TO126 case styles.
How can I find suitable replacements since Denon/Marantz are of no help at all?
 
bigdrums925 3/22/2018 7:48 PM
ANYONE?
 
nosaj 3/22/2018 8:11 PM
Quote Originally Posted by bigdrums925 View Post
No printing on the transistor is same as schematic 34-1013
716 follows that Marantz # however
i have found some that are hard to read and sometimes a white crayon or even rubbing pencil lead on them will uncover what I'm looking for. I also found this may or maynot help
[ATTACH]47757[/ATTACH]

nosaj
more detailed info
[ATTACH]47758[/ATTACH]
 
nickb 3/23/2018 2:05 AM
I'm waiting for the new set of voltages after removing Q5 & Q6.

PS: Responses are sometimes delayed as email notifications are a bit hit and miss.
 
nickb 3/23/2018 2:16 AM
Quote Originally Posted by bigdrums925 View Post
I replaced both Q5 & Q6 as they were bad.
But this did not provide for a sine wave on the collectors of Q13 & Q14 like it did for the other channel.
I removed Q10 and checked. Initially it tested ok but then tested bad.
I suspect both Q9 & Q10 are bad and need replacement.
Now, here's the problem. All I know about them is they are a NPN and a PNP device with Marantz numbers and that they are both TO126 case styles.
How can I find suitable replacements since Denon/Marantz are of no help at all?
What is the pin out?
Do they have a heatsink?

For PNP try a KSA1220A, for NPN KSC2690A assuming there is a heatsink and pin out is ECB [ATTACH]47760[/ATTACH]
 
bigdrums925 3/23/2018 2:44 AM
base collector emitter
Q5 0 1 0
Q6 0 -1.7 0
Q9 .4 42.4 .4
Q10 -1.8 -42.5 -.5
Q13 43 .6 43
Q14 -42.5 -.5 - 42.7

Q10 is removed and tests bad at time of these measurements. Also Q11- Q14 are removed
Q6 was replaced with a A844, cant read Q5 but need to double check it is a PNP although the Marantz schematic shows it a NPN
I assume the new drawing you did is correct that it should be PNP like Q6?
Pin outs on Q9 & Q10 are ECB as are the KSA & KSC you recommend.

I will have to order KSA1220A and KSC2690A since I don't have those.
They are both bolted to metal cylinders that are likely heat sinks with insulators, hard to see.
 
nickb 3/23/2018 2:51 AM
Quote Originally Posted by bigdrums925 View Post
base collector emitter
Q5 0 1 0
Q6 0 -1.7 0
Q9 .4 42.4 .4
Q10 -1.8 -42.5 -.5
Q13 43 .6 43
Q14 -42.5 -.5 - 42.7

Q10 is removed and tests bad at time of these measurements
Q6 was replaced with a A844, cant read Q5 but need to double check it is a PNP although the Marantz schemati8c shows it a NPN
I assume the new drawing you did is correct that it should be PNP?
Q6 is PNP. It is shown wrongly on the Marantz dwg. Q5 ans Q6 are not critical. Not much point in the voltages with missing parts. Things got a bit confused there due to me not getting some responses. Replace the known bad parts first.
 
bigdrums925 3/28/2018 7:55 PM
So both Q5 & Q6 are now 2sa844's
KSA1220A and KSC2690A came in and I replaced Q10 using a KSA1220a
But this did not bring this side to working condition. So here are a new set of voltages

b c e
Q5 0 .9 0
Q6 0 -1.4 0
Q9 .9 42.4 .5
Q10 -1.4 -42.5 -.5

I haven't changed Q9 yet and very difficult to get to but I suppose that should be next
any other suggestions?
 
nickb 3/29/2018 1:28 AM
Those voltages are in the ballpark. But.. earlier you asked about Q5/Q6 and I see I got them mixed up. Q5 ( and Q4) should be NPN and Q6 (and Q3) is PNP.
 
bigdrums925 3/30/2018 9:48 PM
Q5 is a NPN and Q6 is a PNP now.
I don't seem to get a signal through the preamp on the right channel like is present on the left channel.
In fact there seems to be nothing at all signal wise.
Not sure where to look at this point.
Shall I go back and re-measure all the transistor voltages including the preamp?
I haven't removed and checked Q9 but no apparent shorts while in circuit.
But for some reason R42 is burning up after 20 seconds of power up without Q14 or any other outputs installed
 
nickb 3/31/2018 1:57 AM
Removed R14 stuff...oopps!

OK R42.... If R42 is burning up then the voltages are not what was in post #73. At that time the collector of Q10 was -42.5 i.e assumed close to the supply. I don't see the supply volts in the list of measurements ( i.e Q13 and Q14 emitters). It needs to be known to give a complete picture. It may simply be a case of trimmer R27 being too low a resistance - set it to max. IF still cooking redo the voltages.


On the missing signal to the right channel you need to trace down thru the preamp to find where it disappears using your scope.

I just noticed this thing has a CRT display! Kewl!
 
bigdrums925 3/31/2018 2:05 AM
Not R14 but R42 across the output Q14
 
nickb 3/31/2018 3:30 AM
I removed the reference to R14 and updated post #76. I misread....
 
bigdrums925 3/31/2018 1:52 PM
Got the R42 (& R43) burning solved by turning the balance pot R27

new list of voltages I hope are correct at a little less than full variac:

b c e
Q14 -37.9 0 -37.8
Q13 38 0 38
Q10 0 -37.9 0
Q9 0 38 0
Q6 0 0 0
Q5 0 0 0
Q2 0 0 0
Q1002 36.6 1.5 37.8
Q1003 0 .9 1.6
Q1004 .9 -34 -34
Q1001 25.6 1.6 25.9
Q1005 .8 -33.7 1.6
Q1006 -33.7 -1.4 -34

There are probably discrepancies here but lets see if I can make any sense of it with your help
Thanks
 
nickb 3/31/2018 2:57 PM
Given that the output node is correct at 0V I suspect that Q1004 collector at -34V is likely a typo and that things are basically OK with the power amp DC. Can you work thru the preamp so find where the signal disappears?
 
bigdrums925 3/31/2018 10:53 PM
IT WORKS! Thank you so much. and especially for the drawing. How do you do these so quickly?
I'm gonna put all the pieces and parts back together
I'll report back one way or another
BTW what should I set the idle current at? And where should I measure from?
 
nickb 4/1/2018 1:25 AM
Yea! If you have the new reference diodes fitted follow the procedure on pg 14 of the schematics, basically 80mV across R35 and R36.

That is an unusually high bias current given there are no ballast resistors in the output IMHO. If you have the old diodes fitted I would be more conservative. Hook up a dummy load and drive and a few Vpp into it. Gradually increase the bias current until the crossover notch just disappears and checking (with zero signal out) that the drop across R35 or R36 is no more than 30mV. This is a rare case where a distortion analyzer would be the ideal tool.

I've been drawing schematics for (many) years so have had lots of practice I guess. Final version [ATTACH]47947[/ATTACH]
 
tonebells 4/2/2018 4:44 AM
Great job getting it going.

Tony
 
bigdrums925 4/6/2018 10:29 AM
Once again thanks for all the help. Pretty sure I could not have done this without, err I'm sure I could not.
The client was ecstatic about getting his nearly 50 year old receiver going again. He bought it new 1969!
You guys are the best
 
bigdrums925 5/21/2018 9:52 PM
This receiver has come back more than once since it was finished. In each case the output transistors eventually had to be replaced as well as the current limiters. At least once it was because my probe shorted out due to the very compact space the amp components are arranged. I would like to know what would happen if the PNP/NPN output transistors were reversed?
 
The Dude 5/21/2018 10:00 PM
It wouldn't work and would blow a fuse almost immediately.
 
nickb 5/22/2018 1:07 AM
Ideally, you will have to figure out why. It's either too much current, too much voltage, or secondary breakdown which is a bit of both.

My money is on current due to thermal issues and that's easy enough to test for. Run it into a dummy load at half power while monitoring the drop across R35 (80mV at idle). Do it for say one minute and then check the drop across R35 again and check it has not increased. Repeat several time to get the amp hot, checking each time and stop if the voltage gets any higher than (say) 100mV.
 
52 Bill 5/22/2018 9:50 AM
And another thing to ask the customer about are the speakers and wiring that this is being connected to at his location. Fixing the amp is only part of the equation. If the amp is being hooked up incorrectly or to a load that is too low for the amp to handle, it can cause damage to an otherwise working unit.
 
bigdrums925 5/22/2018 12:42 PM
What do you think about using a variac with a light bulb limiter in an effort to prevent destroying any more components in an amp?
Reason I ask is.....I often find myself ramping up the variac carefully monitoring the amp meter I added to it to prevent such things.
It has a 1.5 amp scale. Usually I see the current rise slightly before settling down after a peak of about .7 amps to settle down to maybe .3 -.4 amps or less depending on the design of the amp.
However tube amps often will need a bit more and idle at a higher level I have noticed.
This particular Marantz unit has the tube scope display built into its circuit and idles around .8 amps if I recall correctly.
So I am leery to push the current because I've blown so many of the output transistors and had to replace them at $10 ea.
Obviously I don't want to blow any more of them.
When I remove the output transistors (on the right channel) the current draw is very low all the way up to 100% variac.
I've A-B DCR'ed to ground all the points comparing the L&R amps which reveals no real differences.
The only thing left to do is remove the output transistors and power up to check the voltage maps again.
Comments?
 
olddawg 5/22/2018 4:52 PM
Quote Originally Posted by 52 Bill View Post
And another thing to ask the customer about are the speakers and wiring that this is being connected to at his location. Fixing the amp is only part of the equation. If the amp is being hooked up incorrectly or to a load that is too low for the amp to handle, it can cause damage to an otherwise working unit.
In most shops I worked in we had printed notes that were taped to the unit after an output failure callback that said, "No further repairs would be done without the inspection of customers speakers and wiring.." In old days it was especially problematic with screw type terminals. People tend to strip wire back a couple of inches and they touch.
 
The Dude 5/22/2018 5:01 PM
I had a receiver returned a couple of times years ago. The customer lived nearby, so I went over to his house. His pet rabbit had chewed through the speaker wires. Sorry, I'm not going to warranty that!
 
Leo_Gnardo 5/22/2018 5:28 PM
Quote Originally Posted by bigdrums925 View Post
Comments?
Time to "think outside the box." In this case, the box that holds the Marantz 18. 52 Bill, olddawg and The Dude just gave you some important suggestions. I hope you'll follow through on them and hopefully head off another transistor meltdown.
 
The Dude 5/22/2018 5:43 PM
Not to hype on it, but...... Another time, a customer volunteered that he had built his own stereo speakers. Each one had 4) 6x9 4 ohm car speakers wired in parallel giving him a one ohm load per channel. Unfortunately, you never know what the customer is doing with the amp after you fix it. You can either find out and make him bring in the speakers and wires, or keep fixing the amp for free.
 
bigdrums925 5/22/2018 6:28 PM
I don't have the idle current set to 80mV anymore in an attempt to keep the current draw down during turn on.
Somewhere in this thread was a comment that 80mV seems high even though the service manual recommends it.
At one point I attempted to reduce it a little as a final courtesy but the access hole shorted to the metal trim pot slot and bam, had to replace the power transistors again.
I know I'm supposed to do that with an insulated tool but the access is quite small and the pot hard to turn. My expensive and embarrassing mistake.

The bias/current trim is set as low as I could make it, referencing my amp meter on the variac because I can't get to full power up yet.
However, with the 8 ohm dummy load and an 800 hz signal, volume at 50% & 50% variac, the voltage drop is 6mV sometimes less.
So I increased the variac to 54% where it showed a .3 amp draw on my amp meter. This raised the voltage drop to 105mV.
Nothing seems to be getting hot yet. But what do I do next and still insure I don't risk blowing any more expensive parts?
In other words how far can I push this test? Until I see current draw of .8 - 1.0 amp perhaps?
I can surmise the voltage drop across R35 would be as high as 300-500mV at that variac level.
Or is temperature the major concern here? I have a digital infrared thermometer if that is the case.

BTW I can't be absolutely certain but believe the underlying issue with the returns is something I missed or a combination of small things that begin to fail after time, not an issue of user error. Normally I am very suspect of user errors but not in this case. That with not knowing exactly what parts to replace with what currently available parts & which numbers has me on edge. Thanks Marantz! I thought them better than that.
For what its worth it tests fine here, but I should probably be running it harder and longer before returning it to the customer to ferret out any possible hidden issues.
It's rather old and difficult to work on particularly considering how well loved these old Marantz's are. Seems whatever I do to it has a high risk of another failure.
 
bigdrums925 5/22/2018 6:31 PM
advice well taken dude. I think we could be bros from different mothers!
Everyone else as well. I will double check for any issues on his end

Leo: I got it. and yes, this group of extremely talented and experienced techs is the best! Keeps me in business.
Hopefully I can be of similar service down the line.
Thank you all.....
 
g1 5/22/2018 7:02 PM
Quote Originally Posted by bigdrums925 View Post
When I remove the output transistors (on the right channel) the current draw is very low all the way up to 100% variac.
I'm not sure if I'm understanding correctly, do you mean current draw for the whole amp? So left side draw is low but with right side it is much higher?
If that is the case, I would not release the amp again until you can get the currents roughly equal.
 
nickb 5/23/2018 1:02 AM
Quote Originally Posted by bigdrums925 View Post
I don't have the idle current set to 80mV anymore in an attempt to keep the current draw down during turn on.
Somewhere in this thread was a comment that 80mV seems high even though the service manual recommends it.
At one point I attempted to reduce it a little as a final courtesy but the access hole shorted to the metal trim pot slot and bam, had to replace the power transistors again.
I know I'm supposed to do that with an insulated tool but the access is quite small and the pot hard to turn. My expensive and embarrassing mistake.

The bias/current trim is set as low as I could make it, referencing my amp meter on the variac because I can't get to full power up yet.
However, with the 8 ohm dummy load and an 800 hz signal, volume at 50% & 50% variac, the voltage drop is 6mV sometimes less.
So I increased the variac to 54% where it showed a .3 amp draw on my amp meter. This raised the voltage drop to 105mV.
Nothing seems to be getting hot yet. But what do I do next and still insure I don't risk blowing any more expensive parts?
In other words how far can I push this test? Until I see current draw of .8 - 1.0 amp perhaps?
I can surmise the voltage drop across R35 would be as high as 300-500mV at that variac level.
Or is temperature the major concern here? I have a digital infrared thermometer if that is the case.

BTW I can't be absolutely certain but believe the underlying issue with the returns is something I missed or a combination of small things that begin to fail after time, not an issue of user error. Normally I am very suspect of user errors but not in this case. That with not knowing exactly what parts to replace with what currently available parts & which numbers has me on edge. Thanks Marantz! I thought them better than that.
For what its worth it tests fine here, but I should probably be running it harder and longer before returning it to the customer to ferret out any possible hidden issues.
It's rather old and difficult to work on particularly considering how well loved these old Marantz's are. Seems whatever I do to it has a high risk of another failure.
So you are saying that the idle current on one side is high while the other is high, even too high at 54%? Then you need to root cause that.

It's not a good sign that you cannot get to zero idle current as R27 can be set to zero. That will turn Q2 off leaving just the bias regulator diode in circuit implying that it is bad ( this was the RH channel - right?). Measure the voltage across C29 with R27 set to lowest idle current and report the drop across R36. Don't let the drop across R36 go over 100mV (say). Also check R37 are R42 are OK.

Leave the load off until you get the idle current sorted. Yes, the idle current in the service manual is very high. Personally I'd set it much lower (like a tenth of that) by using a scope or THD analyzer. What does the good channel take? Maybe use that as a guide.


Yes, temperature is a concern as the transistors will fail if the junctions get hotter than about 120C.
 
bigdrums925 5/23/2018 5:50 PM
I think I've found where the problem is located. R36 looks like a potentiometer with only 1 terminal while using the metal case as the other contact.
I would think there is a wiper inside like a regular pot and that reversing the leads while measuring the resistance of the pot directly would give the same resistance.
On the R channel amp, the problem child, it shows the same value which depends on the adjusting position, yet the same in either direction
But on L channel amp I get a diode reading, infinity in one direction, about 900 ohms in the other.
So I will probably have to unsolder a bunch of parts to get R36 out to see how it works. Seems odd to me because I'm measuring directly from the case to the only terminal.
I realize of course I must be measuring through the bias control diode, but I can't see well enough to see why.
I'll report back when I know more

It's not a good sign that you cannot get to zero idle current as R27 can be set to zero. That will turn Q2 off leaving just the bias regulator diode in circuit implying that it is bad ( this was the RH channel - right?). Measure the voltage across C29 with R27 set to lowest idle current and report the drop across R36. Don't let the drop across R36 go over 100mV (say). Also check R37 are R42 are OK.


I think C29 is mislabeled on the new drawing and should be labeled C25 (220nf) because both the original and new drawing show a C29 being located near Q10 and at 470pf.
Both the L & R channel bias regulator diodes measure good in circuit, 862 ohms/infinity. Strange looking things and Marantz p/n on them.
 
The Dude 5/23/2018 6:33 PM
I'm looking at the schematic in your first post. Is that the one being used here? If so, R36 is shown as a .47 ohm 5W resistor- not variable, so it doesn't jive with your post. Can you clarify? Without knowing for sure what part we're discussing, I'd be more apt to believe that there is an open junction (either diode or transistor) on right/problem child channel.
 
g1 5/23/2018 7:00 PM
R26 not R36? (and R27 for other channel) It is drawn as a rheostat so the actual part may only have 2 contacts. I'd expect it to measure the same with probe both ways when using the resistance (not diode) range.
 
The Dude 5/23/2018 7:10 PM
Agree. It should read 2.5k at one end of its travel and near shorted at the other end, if that's the VR we're talking about. The two channels won't read exactly the same unless the rheostat is adjusted for the same resistance.
 
g1 5/23/2018 7:12 PM
And if you do mean the rheostat (R26/R27), and you were using the diode range, do diode checks on B-E junction of Q1 & Q2.
 
bigdrums925 5/23/2018 8:03 PM
For some reason I am getting identical readings both directions on the R channel rheostat
But not on the working L channel
Since it seemed all other resistance & voltage measurements similar except for bias, it makes me think this must be source of the problem

I recall finding many errors in the original Marantz drawings so I'm not sure I'd trust them much. Besides whom else in 1969 would use outsourced parts branded
with only their own proprietary numbers, then let all that critical information get lost forever. I actually had a lot of respect for Marantz until working on this unit.
Some areas have modular circuit boards, while critical higher voltage areas, power amp section looks like a first attempt by a junior HS kid doing point to point wiring
with multiple components stacked on top of each other and almost no way to identify (or see) which parts correspond to which on the drawings. The bias control diodes
for example are buried under the related transistor and capacitor and look like a box capacitor not a diode. I didn't even know it was down there because I couldn't see it.
At least 6 other critical junction areas and can't be probed safely without risk of shorting out. Worse, some measurements can't be made in an energized state. And it's all tucked not so neatly under the chassis lips to further prevent access.
Even difficult unsoldering is common to check individual parts, but in this case many leads come together haphazardly with no support and very close to other terminals.
So removing 3 or more parts just to see the suspect is the norm. Forgive my rant.

So I don't know what to do now cause the working channel is the one that differs from what the drawing(s) imply.
All I know at this point is I have the bias trim as low as I can go on the bad channel and can only variac to 50% before the voltage drop goes through the roof. 49% is stable
but go 51% the current draw climbs rapidly but predictably, but not the voltage drop which rises very rapidly so I can't test very well.
 
bigdrums925 5/24/2018 1:18 AM
I unsoldered the trim pot and Q2 is soldered to that. Q2 tests bad. So how do I know what to replace it with since its Marantz's proprietary number 34-1014?
 
bigdrums925 5/24/2018 1:28 AM
Quote Originally Posted by The Dude View Post
I'm looking at the schematic in your first post. Is that the one being used here? If so, R36 is shown as a .47 ohm 5W resistor- not variable, so it doesn't jive with your post. Can you clarify? Without knowing for sure what part we're discussing, I'd be more apt to believe that there is an open junction (either diode or transistor) on right/problem child channel.
Frankly Dude, I can never tell myself which drawing I'm referencing at any given moment because I seem to have to jump around to verify which part I'm working on.
But ya, its the rheostat R27. Sorry bout that.
Again turns out you were right because Q2 is bad and I need to find a replacement.
Can anyone tell me what common transistor I can use as a replacement since it's label Marantz 34-1014
 
nickb 5/24/2018 2:00 AM
Quote Originally Posted by bigdrums925 View Post
Frankly Dude, I can never tell myself which drawing I'm referencing at any given moment because I seem to have to jump around to verify which part I'm working on.
But ya, its the rheostat R27. Sorry bout that.
Again turns out you were right because Q2 is bad and I need to find a replacement.
Just about any small low voltage signal si NPN transistor will work.
 
bigdrums925 5/24/2018 3:01 AM
Great! I'll see what I can find
 
bigdrums925 5/24/2018 12:50 PM
Crap, now I see with a diode meter test that CR18 is open in both directions too.
How can I find a workable replacement?
Help!

Oh wait! my meter wasn't energizing the Vf=2.
So yea, the diode CR18 is good. put in the new transistor Put the whole thing back together and the bias is holding steady!
Turned on the unit and no excessive current draw. Doing the listening test now.
All is well in the neighborhood
Thanks guys!
 
nickb 5/24/2018 2:23 PM
Quote Originally Posted by bigdrums925 View Post
Crap, now I see with a diode meter test that CR18 is open in both directions too.
How can I find a workable replacement?
Help!
Try measuring the voltage across it by forward biasing using a 9v battery and 10K resistor in series. Your meter is expecting an ordinary diode and might be giving you misleading readings. Expect about 1.95v or so.
 
tonebells 5/24/2018 3:25 PM
I have two of these from a parts unit they both diode test on my fluke 117 at 1.66 and 1.69. They test 2.02 and 2.15 on my Peak DCA55. I have seen where someone used three 1N4148s as a replacement.

Tony
 
olddawg 5/24/2018 4:38 PM
Are you dealing with a "stacked" diode in the bias circuit. Usually the schematic symbol looks like a series of diodes with 2, 3, and even 4 junctions in a single package. Normally it's 3 junctions with a foreword voltage drop of about 2v. I've used 3 rectifier diodes in series many times to replace these. They usually attach to the heat sink and are the first thing novice techs seemed to break back in the day.
 
bigdrums925 5/24/2018 8:35 PM
Yes ~ 2 V. I compared the new drawing and the original. At first I didn't know what Vf meant. Looked at the original and could see there 3 stacked diodes. My regular meter didn't read them, but tried the new better one and it wasn't bad after all. Everything seems to be working fine now and test ran it medium hard for an hour. Putting it back in it's pretty wood case now. Thanks again. If this forum was on Yelp I'd give 5 stars!
Set the bias at 25mV