SoulFetish 6/12/2017 5:57 PM
Look who's all grown up! Finally able to pull the trigger and get an oscilloscope
I just found a great deal on a Rigol DS1102E 100MHz Digital scope and bought it. Should be here by Wednesday and I can't friggin' wait!
These have been really well reviewed by owners and at a price of $190 (lightly used) w/$10 shipping and a warranty, I thought it was a lot of value.
This is long overdue, and it just so happens that I really need one right now for a project.
I don't think it comes with any probes, so what should I be looking for in that regard?
 
nosaj 6/12/2017 7:47 PM
Quote Originally Posted by SoulFetish View Post
I just found a great deal on a Rigol DS1102E 100MHz Digital scope and bought it. Should be here by Wednesday and I can't friggin' wait!
These have been really well reviewed by owners and at a price of $190 (lightly used) w/$10 shipping and a warranty, I thought it was a lot of value.
This is long overdue, and it just so happens that I really need one right now for a project.
I don't think it comes with any probes, so what should I be looking for in that regard?
Was there just one?

I bought 1x-10x 100mhz probes for my 20mhz scope. They've been just fine. Just make sure your probes voltage rating is good and know what the input voltage max on the scope is.

nosaj
 
g1 6/12/2017 8:25 PM
Quote Originally Posted by SoulFetish View Post
I don't think it comes with any probes, so what should I be looking for in that regard?
Depends on what the specs are for the AC and DC voltage it can handle.
 
Enzo 6/12/2017 9:56 PM
Right now you just need to learn to use the scope, and for that matter when to stop scoping every darn thing in sight. I have used the basic cheap probes on the market for years, and they have worked fine for me. I am sure the $150 probes work well also, but $30-40 has worked in my case.

We almost always use probes on X10 mode. I have bought probe sets with dedicated X1 and X10 probes, and wind up using the X10 most of the time. But the X1/X10 switch on the probe is useful. I run X10 mostly, but now and then I am searching a low level signal or maybe a noise signal, and X1 is useful for that. SO get yourself a probe with the switch.

I used to do more business with MCM, and bought probes there. I have a local electronics parts store, and I have bought them there.
 
TimmyP1955 6/13/2017 6:04 PM
Put a piece of tape over the probe's 1x/10x switch, so you cannot accidentally switch it to 1x and blow the input of your scope.
 
nosaj 6/13/2017 6:11 PM
Quote Originally Posted by TimmyP1955 View Post
Put a piece of tape over the probe's 1x/10x switch, so you cannot accidentally switch it to 1x and blow the input of your scope.
Good idea, do you know that one from experience?

nosaj
 
Randall 6/13/2017 7:45 PM
Quote Originally Posted by TimmyP1955 View Post
Put a piece of tape over the probe's 1x/10x switch, so you cannot accidentally switch it to 1x and blow the input of your scope.
This I want to see the responses to. I have used the same scope for 30 years with different probes, switching them back and forth 1X/10X and never had a problem. Mine has a 600v max P-P and DC rating, and I know I've exceeded that at least more than once, especially the P-P.
 
The Dude 6/13/2017 8:15 PM
What brand and model scope is it?
 
drewl 6/13/2017 8:33 PM
Congratulations!
I have at least three around here somewhere, and a ton of other test equipment.

Fortunately I used to work on test equipment back in the '80's.

Let me tell you about TUBE oscilloscopes!
Got a bunch of RCA 6550's that were in the Tektronnix scopes, as well as little spools of silver solder!

We used to joke that techs in the old days must have been huge hulking guys to lug around 80lb "portable" oscilloscopes.

Love them switchable x1/x10 probes.
We used to get free samples from a local mfgr.
 
g1 6/13/2017 9:48 PM
Quote Originally Posted by TimmyP1955 View Post
Put a piece of tape over the probe's 1x/10x switch, so you cannot accidentally switch it to 1x and blow the input of your scope.
One thing that was discussed in another thread, when you are on AC coupling, the 10x setting does not reduce the DC applied to the scope input.
 
Mick Bailey 6/14/2017 12:42 AM
What overload protection is on those scopes - would it need an additional input protection circuit? An accidental slip from scoping an AC grid signal on a 6L6 socket could give you maybe 460v on the input. Tube equipment has a much greater voltage range than probably any other gear you're likely to work on. For me, perhaps I'd be looking to build a little limiter/protection box if I were to move away from my Tektronix scope.
 
drewl 6/14/2017 3:01 PM
For our spectrum analyzers at work we made up probes with a cap on them to keep dc out.
They can only handle a few volts dc.

You could use something similar for scoping high voltage, with like a 1kv cap.
 
nsubulysses 6/14/2017 3:19 PM
scopes are fun. I have a bunch of 50s-80s tektronix scopes that are usually found on craigslist or ebay for free-$100.

I have one new scope, Rigol DS1054Z . It is pretty inexpensive but cool and does A LOT. I use it as my reference for my old scopes to check their cal, and usually they are amazingly either in cal or not far off. I use the rigol as my main scope because it's fast and easy (lots of digital measurements on the screen rather than count the graticules and get out the calculator) and has 4 channels.

Enjoy

Those rigol probes have a real cheap-ass feel compared to the old tektronix ones but a good scope none the less, and maybe not a fair comparison at all anyway

RIGOL RP2200 Passive Oscilloscope Probe Kit (Qty 2) all Accessories, Brand New!

make em an offer they can't refuse
 
Chuck H 6/15/2017 11:16 AM
Quote Originally Posted by Enzo View Post
Right now you just need to learn to use the scope, and for that matter when to stop scoping every darn thing in sight.
I laughed out loud reading this. Even though I wasn't always sure what I was looking at I still wanted to know what it looked like. There are a lot of on line sources for learning just what you're actually looking at. More important would be how to set up the scope for easy figuring. Time well spent for a new scope owner. Sometimes I just need to "see" what's going on and I just twiddle for the best visual. Sometimes I want more info and the easiest math conversion. About the time you stop scoping everything in site is when you get to reading about how to use the thing Not that I've entirely learned how to use my scope, but it IS a bench tool now and not a novelty.
 
Enzo 6/15/2017 12:07 PM
I see it over and over. Like when someone finally gets and ESR meter. All of a sudden they measure ESR on all the caps they see, and ESR becomes the most important thing since air to breath. With scopes, guys find that no matter what they are looking at, if they turn up the vertical far enough they eventually see some sort of noise waveform, or the local AM radio station, or SOMEthing. I made up the term "trace chasing" for the phenomenon. You chase after a trace long enough, you'll find one.
 
Chuck H 6/15/2017 6:06 PM
Quote Originally Posted by Enzo View Post
... turn up the vertical far enough they eventually see some sort of noise waveform, or the local AM radio station, or SOMEthing. I made up the term "trace chasing" for the phenomenon. You chase after a trace long enough, you'll find one.
Still laughing. I did that too. Not much though because I always have other amps around for a reality check.

I did have an odd thing happen once where micro scanning the waveform helped. Sometimes with tone stacks the HP cap will create a distortion artifact when there is a lot of LF being "blocked" (if that's even the right way to think of it?). I had an amp that would crackle just audibly on some clean tones and I traced it to the treble cap. Replacing the cap didn't help. So I took a good close look at the wave form and saw the artifact. I struggled for hours trying to mitigate it in one way or another before I opened up another amp and probed it for a reality check. It turns out that this is normal, but worse on some amps and more or less audible in different overall designs. In this case the artifact was greater than usual and the design really allowed it to be heard. It was a silver face Champ. I fixed it by reducing gain to the tone stack a little, bumping the gain in the following stage and I can't remember what all else. But it was the scope that helped me find it and the scope that allowed me to see it was "normal"-ish and it was the scope that allowed me to monitor progress in the circuit modifications. I did a lot of mods to that one and the owner calls it his little *umble
 
TimmyP1955 6/15/2017 6:40 PM
Quote Originally Posted by nosaj View Post
Good idea, do you know that one from experience?

nosaj
No, but Murphy catches up with us all eventually ;-(
 
SoulFetish 6/19/2017 12:46 PM
Quote Originally Posted by Enzo View Post
Right now you just need to learn to use the scope, and for that matter when to stop scoping every darn thing in sight.
Too late. I'm a scopin' Mutha' F**ker now, Enzo.
If it beeps, bloops, blinks, or buzzes, it's getting scoped. I'm gonna scope like LT scopes. Hell, I'm gonna' Scope like The State of Tennessee vs. John Thomas for violating the Butler Act.... in 1925.
 
SoulFetish 6/19/2017 1:51 PM
do you guys use active differential probes to measure high p-p voltages (ie. plate)? Or, passive 100x probes?
 
nickb 6/19/2017 4:13 PM
Quote Originally Posted by SoulFetish View Post
do you guys use active differential probes to measure high p-p voltages (ie. plate)? Or, passive 100x probes?
Passive 100x for me. I doubt anyone would use a diff probe for tube tests unless it's a lab situation
 
SoulFetish 6/19/2017 5:29 PM
Quote Originally Posted by nickb View Post
Passive 100x for me. I doubt anyone would use a diff probe for tube tests unless it's a lab situation
Are most 100x high voltage rated (one would think)? I should probably look for at least CAT II, yeah?
 
Chuck H 6/19/2017 7:53 PM
I only have a 10x/1x switch probe. My scope has a max 400 input voltage. I haven't had a problem. I don't scope the power tube plates much though. Usually if I'm already out that far on the signal chain I'm scoping the output jack.

What is the input voltage of your scope?
 
SoulFetish 6/19/2017 10:15 PM
Quote Originally Posted by Chuck H View Post
I only have a 10x/1x switch probe. My scope has a max 400 input voltage. I haven't had a problem. I don't scope the power tube plates much though. Usually if I'm already out that far on the signal chain I'm scoping the output jack.

What is the input voltage of your scope?
Same. 400VDC or peak AC. but can withstand transients to 1000V for short a duration. Now I'm paranoid that I'm going to ground the probe out to a +V terminal by accident.
 
Chuck H 6/19/2017 10:25 PM
Quote Originally Posted by SoulFetish View Post
Now I'm paranoid that I'm going to ground the probe out to a +V terminal by accident.
Yeah, don't do that.

And you almost certainly won't. It's a hard mistake to make when the CHASSIS IS RIGHT THERE!!! Unless you're measuring a swing voltage across two points. But that's usually pretty specific.

10X means you can have peaks to 4000V on your scope using a 10X probe. I think you'll be OK if you're paying attention. Though I admit that I've had a couple of close calls with "my" scope by NOT paying attention.
 
Justin Thomas 6/19/2017 11:14 PM
Probes were cheap enough; I got a x1/x10 AND a x10. And I may be willing to make up whatever little safety gadgets I have to to spare my scope. When I get one! Eventually... I try not to look at these kinds of things as disposable, even if I <DO> get a great deal. That $10 multimeter is worth playing safe with; you'll be that much more conscientious later on with the good stuff. And who knows when the next great deal will come along? Besides, less spent on blown-up equipment = more spent on amp parts!

Justin
 
nickb 6/20/2017 1:12 AM
Quote Originally Posted by SoulFetish View Post
Are most 100x high voltage rated (one would think)? I should probably look for at least CAT II, yeah?
The one I have is rated at 1200V AC+DC.


My scope has a limit of 150V so it's really not the best solution for probing anywhere where you need AC coupling and where there is more than 150V DC. When the scope is switched to AC the DC input voltage appears across that cap. It's quite common to hear people use a capacitor on the end of the probe to look at AC signals in the presence of high DC and I do this often myself, but there is a short period of time when you first probe during which that scope input cap charges and nearly high DC voltage appears across the scope input cap. Keep the cap small say 1,000pF for a x10 10Mohm probe. The best solution is really an external attenuator with switchable AC coupling and a limiter to prevent scope damage - Juan has a posted a suitable design on these pages before.
 
Enzo 6/20/2017 5:51 AM
ANyone really concerned could make a tiny voltage divider with a couple resistors and clip the probe to it, then use an additional probe to the circuit.
 
SoulFetish 6/20/2017 8:47 AM
Fahey (or anyone), if your out there, do you have alink to the probe topic that Nick was refering to?
 
Tom Phillips 6/20/2017 8:57 AM
Quote Originally Posted by SoulFetish View Post
Fahey (or anyone), if your out there, do you have alink to the probe topic that Nick was refering to?
There is a good bit of information in the discussions at http://music-electronics-forum.com/t31492/ and http://music-electronics-forum.com/t37999/

Still looking for the discussion that includes Juan's attenuator that will substitute for a good HV probe.
Edit: Juan's post is in the discussion at Test bench amp setup advice - Music Electronics Forum
 
nickb 6/20/2017 10:55 AM
Quote Originally Posted by SoulFetish View Post
Fahey (or anyone), if your out there, do you have alink to the probe topic that Nick was refering to?
Here is my version. Ideas shamelessly stolen from Juan


[ATTACH=CONFIG]43841[/ATTACH]

Oh..., the 1pf is just a guess. It's there to maintain the HF response and can usually be left out. The actual value depends on the zeners and chosen to get a flat top on a square wave. Resistors do have a voltage limitation so a string of six is used to get to 3kV
 
SoulFetish 6/20/2017 11:31 AM
Quote Originally Posted by nickb View Post
Here is my version. Ideas shamelessly stolen from Juan


[ATTACH=CONFIG]43841[/ATTACH]

Oh..., the 1pf is just a guess. It's there to maintain the HF response and can usually be left out. The actual value depends on the zeners and chosen to get a flat top on a square wave. Resistors do have a voltage limitation so a string of six is used to get to 3kV
Okay, i dig that. I'm pretty much looking at ceramics for those 3KV caps, yeah?
Should I include a capacitive divider for the attenuator? I guess you have the 10X probe function as well. May be overkill.
 
nickb 6/20/2017 11:47 AM
Quote Originally Posted by SoulFetish View Post
Okay, i dig that. I'm pretty much looking at ceramics for those 3KV caps, yeah?
Should I include a capacitive divider for the attenuator? I guess you have the 10X probe function as well. May be overkill.
The ratio is 100:1, not 10:1. The capacitive divider is already there and consists of the zeners in parallel with the scope input in the tail and the nominal 1pF in the head of the divider.
 
SoulFetish 6/20/2017 12:29 PM
Quote Originally Posted by nickb View Post
The ratio is 100:1, not 10:1. The capacitive divider is already there and consists of the zeners in parallel with the scope input in the tail and the nominal 1pF in the head of the divider.
Oh dude,my bad. I had a momentary lapse and was thinking about capacitor dividers backwards instead of how the ratio
Works with the reactance. Im sorry. The example was clear, my mind was not
 
Chuck H 6/20/2017 11:24 PM
FWIW Enzo's capacitor in series with the scope' thing is great for monitoring PI AC circumstances. PI measurements are sometimes problematic because of the high input impedance. A series cap solves for this WRT AC measurements.
 
nickb 6/21/2017 12:37 AM
Quote Originally Posted by SoulFetish View Post
Oh dude,my bad. I had a momentary lapse and was thinking about capacitor dividers backwards instead of how the ratio
Works with the reactance. Im sorry. The example was clear, my mind was not
Mea Cupla too: I swapped the labels for AC and DC on the switch
 
SoulFetish 6/24/2017 4:19 AM
Nick, should I use a short lenght of RG58 (or some other 50 ohm cable) to couple the attenuator to the scope?
 
nickb 6/24/2017 5:58 AM
Quote Originally Posted by SoulFetish View Post
Nick, should I use a short lenght of RG58 (or some other 50 ohm cable) to couple the attenuator to the scope?
Something screened, flexible and rated for these voltages is good. The impedance is not an issue.
 
SoulFetish 6/24/2017 6:28 AM
Yeah, the probe I have now isnt rated for the high voltage side of this circuit. Im going to need something suitable.
 
nickb 6/24/2017 6:41 AM
Quote Originally Posted by SoulFetish View Post
Yeah, the probe I have now isnt rated for the high voltage side of this circuit. Im going to need something suitable.

Afterthought: Whatever you use keep it a short as possible. A foot of twisted HV pair might be good. The objectives are insulation and low capacitance. If you can build the megohm resistors right at the tip that would be ideal - just like a real probe. Then longer screened cable would be fine as it's capacitance appears across the output where the impedance is lower and that is a good thing. You seem to have excellent build & mechanical skills (jealous) so I'm sure you'll come up with something
 
Tom Phillips 6/24/2017 8:48 AM
Quote Originally Posted by SoulFetish View Post
Nick, should I use a short lenght of RG58 (or some other 50 ohm cable) to couple the attenuator to the scope?
Quote Originally Posted by nickb View Post
Something screened, flexible and rated for these voltages is good. The impedance is not an issue.
I suggest that you just use a X1 scope probe. Referring to the diagram in post #30 just connect the probe to the nodes after the attenuator labeled “To scope.”
 
nickb 6/24/2017 10:57 AM
Quote Originally Posted by Tom Phillips View Post
I suggest that you just use a X1 scope probe. Referring to the diagram in post #30 just connect the probe to the nodes after the attenuator labels “To scope.”
I had thought about that dismissed it on grounds of not specified for 3KV.
 
Tom Phillips 6/24/2017 11:04 AM
Quote Originally Posted by nickb View Post
I had thought about that dismissed it on grounds of not specified for 3KV.
I meant to use the 1X probe to connect between the attenuator output and the scope. If the voltage at the output of the atternuator is 3kV then somethings really amiss and you can't hook it to the scope input with a wire anyway.
 
Chuck H 6/24/2017 1:09 PM
For a 3KV rating you'll need to put a bunch of resistors in series anyway. This almost calls for it's own housing. Something like a Bic pen case with a probe at the tip end then a shielded cable coming out of the other. Now the cable only needs to handle 300V for a 3KV input at the Bic probe tip. Then some way to couple that cable to the 1X probe.
 
SoulFetish 6/24/2017 2:01 PM
Quote Originally Posted by Chuck H View Post
For a 3KV rating you'll need to put a bunch of resistors in series anyway. This almost calls for it's own housing. Something like a Bic pen case with a probe at the tip end then a shielded cable coming out of the other. Now the cable only needs to handle 300V for a 3KV input at the Bic probe tip. Then some way to couple that cable to the 1X probe.
This is what i was thinking. I was thinking about finding or fashioning something ceramic i cound use as a probe head/tip and building in in there.
 
Tom Phillips 6/24/2017 2:33 PM
Quote Originally Posted by SoulFetish View Post
This is what i was thinking. I was thinking about finding or fashioning something ceramic i cound use as a probe head/tip and building in in there.
Or you could just buy a used Tektronix Model P6007 100X Probe. If you are patient, you can get one for a really reasonable price. Here is a link to a completed eBay sale for $20 including shipping. ( Tektronix Probe 2883619. P6007, BNC, 6, 100X~ 2.2pf. 10M? | eBay )

The P6007 is the model I posted about in the thread at http://music-electronics-forum.com/t31492/. It's design is such that it attenuates both the AC and the DC voltage. Therefore, the P6007 does not exhibit the problem that allows the capacitor inside the scope to charge to the full un-attenuated DC voltage being probed. The MEF thread I referenced already explains this and contains the Tek Probe circuit so I won't repeat the info here. The designs and performance of commercial 100X probes vary. One needs to check the specifications and read the operating manuals to determine if the probe will work for your application.

HTH,
Tom
 
nickb 6/25/2017 12:51 AM
Quote Originally Posted by Tom Phillips View Post
I meant to use the 1X probe to connect between the attenuator output and the scope. If the voltage at the output of the atternuator is 3kV then somethings really amiss and you can't hook it to the scope input with a wire anyway.
Ah Tom. - thanks - you made me realise I was answering the question of what to put between the attenuator and the equipment and not the one Cory asked i.e what put between the attenuator and the scope. Duh!

The answer is much the same but without the HV restriction and capacitance is less critical.
 
SoulFetish 7/5/2017 8:31 PM
Quote Originally Posted by Tom Phillips View Post
Or you could just buy a used Tektronix Model P6007 100X Probe. If you are patient, you can get one for a really reasonable price. Here is a link to a completed eBay sale for $20 including shipping. ( Tektronix Probe 2883619. P6007, BNC, 6, 100X~ 2.2pf. 10M? | eBay )

The P6007 is the model I posted about in the thread at http://music-electronics-forum.com/t31492/. It's design is such that it attenuates both the AC and the DC voltage. Therefore, the P6007 does not exhibit the problem that allows the capacitor inside the scope to charge to the full un-attenuated DC voltage being probed. The MEF thread I referenced already explains this and contains the Tek Probe circuit so I won't repeat the info here. The designs and performance of commercial 100X probes vary. One needs to check the specifications and read the operating manuals to determine if the probe will work for your application.

HTH,
Tom
Thanks for the heads up on the Tek P6007. I've been weary of some of the really cheap probes on the market today, particularly when no datasheet is presented.
Sometimes I have to remind myself that it just makes sense to spend the money and buy something, vs making it or finding a way around it.
I don't know what the hell my problem is; I spent over an hour and a half researching solvent dyes for polyvinyl chloride because I have a surplus of white 18AWG UL1015 wire and didn't want to buy more to have different colors. Actually, I do no what my problem is. I'm the perfect storm of cheap, broke, and hubristic. I finally snapped out of it and said to myself "Dude, just pay the $6 a piece for a couple of 25' rolls and pull your head out of your ass".
 
Chuck H 7/5/2017 8:55 PM
FWIW I spend the extra buck a roll on "irradiated" PVC now. It's far tougher and shrinks about 20% of what standard PVC does under the iron. So worth it. It's certainly cheap enough and the results after soldering and construction are better. Heads up though... DO check for voltage rating on the jacket. When you start looking at irradiated PVC you get into the realm of real pro's that know how to spec. So none of the dunderhead work is done for you. The rating on the material might be strictly AC. I had this problem once and had to shotgun change an order to get lead wire appropriate for the DC voltages we use. The vendor got a little grumpy about it and I had to point out that they hadn't specified AC or DC on the voltage rating!!! Sorry I can't remember where I bought it. It was a few years ago and I've barely cracked into the 600 yard rolls But irradiated IS what you want. Offered for our consideration. And irradiated PVC highly recommended by this guy.
 
Justin Thomas 7/5/2017 9:42 PM
I remember my first roll of Teflon wire from Belden. I panicked when I saw the 300V rating AFTER I had punched out the center label and couldn't read it entirely. I called the store I bought it at and they said, "that's when you are using it submerged in gasoline; it's 600V." Huh, never woulda thunk it...

Wow, what a relief... I think.

Justin
 
Chuck H 7/5/2017 10:13 PM
Yeah.?. All kinds of oddness WRT voltage ratings. Why in the hell would they expect anyone to read a spec. and just KNOW "when submerged in gasoline"??? That's just the sort of thing that comes up when you order wire IME. You do learn what to look for, but that doesn't mean it's always represented in completed statements Like we all have extra dough for finding out what we ordered isn't quite right!?! Lazy product descriptions bother the $h!t out of me.
 
SoulFetish 7/5/2017 10:14 PM
Quote Originally Posted by Chuck H View Post
...irradiated PVC highly recommended by this guy.
I dunno' Chuck... Think I can dye that sh*t?
 
The Dude 7/5/2017 10:20 PM
Quote Originally Posted by Chuck H View Post
Yeah.?. All kinds of oddness WRT voltage ratings. Why in the hell would they expect anyone to read a spec. and just KNOW "when submerged in gasoline"??? That's just the sort of thing that comes up when you order wire IME. You do learn what to look for, but that doesn't mean it's always represented in completed statements Like we all have extra dough for finding out what we ordered isn't quite right!?! Lazy product descriptions bother the $h!t out of me.
You just never know when someone might spill a "flammable liquid" inside an amp.
 
SoulFetish 7/5/2017 10:27 PM
Quote Originally Posted by Chuck H View Post
Yeah.?. All kinds of oddness WRT voltage ratings. Why in the hell would they expect anyone to read a spec. and just KNOW "when submerged in gasoline"??? That's just the sort of thing that comes up when you order wire IME.
No doubt. Voltage rating is a moving target anyways. A withstand voltage rating depends on things like temperature, time/duration, frequency, etc. I try and be as thorough as possible when it comes to component data and look at as much graphical detail as is relevant to me. Plus, you have standards like UL and MIL type W which have their own criteria which has to be met in order to get approved for certain classifications.
 
SoulFetish 7/5/2017 10:38 PM
on a side note, you guys ever read something wrong the first time and whenever you see it again after that you keep pronouncing it wrong in you head even though you know better?
The first time I came across the term "irradiated PVC" wire, I read it "irradated". Like, irradating was a mysterious new technique for processing PVC used by manufacturers.