Hi all,

I’m currently adjusting my newly repaired Type 106. Everything is just perfect until I arrive at section 6-14 to 6-17 which call for a sampling osciloscope, and I currently do not have one. Looking at the waveform pictures they have, my unit is apparently out of spec with regards to the Fast Rise +/- outputs, and I need to adjust C107-C118 and C127-C138 (sections 6-16 to 6-17).
The manual does give certain settings for the sampling scope, which of course, not having one, I can’t follow.
Is there anyway I can do that with a regular more “modern” scope? By that I mean setting up my non-sampling scope controls to come as close to show what their sampling scope would with the settings they use?

Thanks

I suspect that you could use an analog scope set to the fastest sweep.  There is nothing fundamental about a digital scope that would make it essential for this calibration.  It depends on the speed.  Back about 55 years ago there were no analog scopes fast enough but today that's not true.
Bob

On Fri, Jan 21, 2022 at 12:00 AM, Bob Albert wrote:

I suspect that you could use an analog scope set to the fastest sweep. 
There is nothing fundamental about a digital scope that would make it
essential for this calibration.  It depends on the speed.  Back about 55
years ago there were no analog scopes fast enough but today that's not true.
Bob

Hi Bob, and thank you.

I also thought the same thing, but not being an expert at these things, I wasn’t quite sure that this was the only reason they used one.
I don’t have anything that modern as a later production DSO, and the fastest scope I have at the moment is a 1GHz DSA 602A.
I’m not quite sure what settings to use in order to conform to what the manual recommends. The reason being that, very often, when you’re not on the right scale, you just don’t see changes when turning pots.

On Fri, Jan 21, 2022 at 12:08 AM, David Templeton wrote:

Any decent modern scopes could do that, they give the seconds per div and
picture of the rise time. Probably need a 2GHz bandwidth to get that 1ns rise
time in single shot.

David

Well, the fastest I have is the DSA 602A with a 1GHz plugin…. Hmmmm…

Don't sweat it.  Sweep as fast as you can and don't turn anything very far.  Why do you think adjustment is needed?
Bob

On Fri, Jan 21, 2022 at 12:18 AM, Bob Albert wrote:

Don't sweat it.  Sweep as fast as you can and don't turn anything very
far.  Why do you think adjustment is needed?
Bob

For starters, I repaired this unit not long ago, and quite a few parts were changed. All the voltages and almost everything up to this part of the calibration was completely off.
But not having a sampling scope, I thought I could get away with it. However, when I tried today to calibrate the HF compensation on a 2235, I realized that whatever I did, it never looked right. The flat top just wasn’t flat at all. It had that big hump just after the overshoot. So I figured I’d check the exact same thing on the DSA (which is calibrated), to see how that looked. And I had the exact same results.
Then I tried to replicate on the DSA what the manual suggested, and I also got very different results.

Here is what the waveform on the 2235 and DSA looks like. Notice the big hump.
https://groups.io/g/TekScopes/photo/271865/3369758?p=Created%2C%2C%2C50%2C2%2C0%2C0

And here are the pictures of me trying to replicate the calibration from the manual. You can definitely notice the big hump I mentioned. Sweeping speeds and vertical are mentioned on the screen (3 pictures at different speeds):
https://groups.io/g/TekScopes/photo/271865/3369759?p=Created%2C%2C%2C50%2C2%2C0%2C0

https://groups.io/g/TekScopes/photo/271865/3369760?p=Created%2C%2C%2C50%2C2%2C0%2C0

https://groups.io/g/TekScopes/photo/271865/3369761?p=Created%2C%2C%2C50%2C2%2C0%2C0

Can you provide a picture with two complete cycles in it (+ output)? Can you describe exactly what is between the generator chassis connector and the BNC on the front of the scope?

On Fri, Jan 21, 2022 at 02:06 AM, tgerbic wrote:

Can you provide a picture with two complete cycles in it (+ output)? Can you
describe exactly what is between the generator chassis connector and the BNC
on the front of the scope?

Hi tgerbic,

Yes of course. This is about 2 cycles of the positive going signal:

https://groups.io/g/TekScopes/photo/271865/3369796?p=Created%2C%2C%2C50%2C2%2C0%2C0

And this the negative going:

https://groups.io/g/TekScopes/photo/271865/3369799?p=Created%2C%2C%2C50%2C2%2C0%2C0

Big difference.

Between the chassis connectors of the 106 and the front end BNC connector of the scope is, in the case of the DSA106A, a 50ohm cable only, as the input is already internally terminated into 50 ohm.
But even if I use a different plugin for which I choose not to use the internal termination, but use a through 50 termination, it’s still exactly the same. It’s also perfectly the same if I use a different cable, or even a cable with a different length. In other words, it’s not from whatever is in between. As clearly seen, the negative going, with the exact same setup, doesn’t have that issue. That is why I believe it comes from the positive output itself.

Regards

Stephen,
This might be relevant so I will respond here. On your DSA602A are you using the 11A72? From some of the settings on the DSA it looks like you are using the scope dc coupled in to 400 Mhz I am assuming a 50 ohm terminator on the cable. 400 Mhz is not fast enough for a Type 106 fast edge. These are 1 ns transition they will need to be viewed at 1Ghz to see what is really going on. I have snapped a photo of how mine looks on the DSA I will upload shortly when the camera gets done dumping to the hard drive. I imagine looking at the transition at a high speed will be revealing. Also make SURE you are on the correct polarity when you are looking at the edge.

The transition is from (voltage) TO ground. So the fast rise edges are negative voltage -> ground. The fast fall is positive voltage -> ground. This really bit me in the butt during a calibration. The PG506 is the same way and not intuitively marked.

Zen

Hi Eric,

Apart from the very first picture where you see the 400MHz of the 11A32, everything else is done with the 11A72 at 1GHz. As you very well know, this plugin is 59Ohm and 1GHz only.

On Fri, Jan 21, 2022 at 04:33 AM, <Zentronics42@gmail.com> wrote:

INTERLEAVED.

Stephen,
This might be relevant so I will respond here. On your DSA602A are you using
the 11A72? From some of the settings on the DSA it looks like you are using
the scope dc coupled in to 400 Mhz I am assuming a 50 ohm terminator on the
cable. 400 Mhz is not fast enough for a Type 106 fast edge. These are 1 ns
transition they will need to be viewed at 1Ghz to see what is really going on.
I have snapped a photo of how mine looks on the DSA I will upload shortly when
the camera gets done dumping to the hard drive.

I imagine looking at the
transition at a high speed will be revealing.

I think I am…

Also make SURE you are on the
correct polarity when you are looking at the edge.

I’m not sure what you mean.

Regards

In looking through the pictures the 2nd picture you posted has me more concerned than the over shoot at the moment. That fast rise looks really bizarre like there is some kind of leakage current escaping through. The fast falls look like they should. But the output of the fast rise is -1V -> ground. But the weird thing is the output wont stay at ground. This one strange.

Zen

Perhaps the problem is far enough back that you should start by looking at the base of Q124 and comparing it to the base of Q103. Then emitter of Q134 compared to Q114 and so on. At some point I would expect something obvious should show up going component by component. Wrong value resistor, C102 leaky/high ESR, bad ground, or defective/open diode. Having two functionally similar circuits should help.

On the fast rise and fast fall edges and waves forms on this unit as well as the PG506 are not symmetric. I got burned because I though fast rise was ground to +1V its not that is the fast fall output. So I was using the wrong output and was wondering why the transition was slow. Your fast fall looks healthy. Fast rise. My gut is telling me there is leaking silicon. But I could be wrong. One of the tings that is bugging me is it cant sustain ground the voltage decays back towards -1V.

Zen

On Fri, Jan 21, 2022 at 05:19 AM, <Zentronics42@gmail.com> wrote:

In looking through the pictures the 2nd picture you posted has me more
concerned than the over shoot at the moment. That fast rise looks really
bizarre like there is some kind of leakage current escaping through. The fast
falls look like they should. But the output of the fast rise is -1V -> ground.
But the weird thing is the output wont stay at ground. This one strange.

Yes. The whole waveform doesn’t look right to me. I’m not good enough to explain it, but it’s just not right.

I’ve just posted a picture with exactly the same settings as yours:

https://groups.io/g/TekScopes/photo/271865/3369907?p=Created%2C%2C%2C50%2C2%2C0%2C0

They look similar…. BUT that’s because we’re only looking at the edge. I’m sure the whole waveform on yours must be pretty similar to the negative going one, meaning “normal”…. I assume you don’t have that huge hump I have. Nor does it’s falling edge look funny as if the first portion had been scooped off.

On Fri, Jan 21, 2022 at 05:20 AM, tgerbic wrote:

Perhaps the problem is far enough back that you should start by looking at the
base of Q124 and comparing it to the base of Q103. Then emitter of Q134
compared to Q114 and so on. At some point I would expect something obvious
should show up going component by component. Wrong value resistor, C102
leaky/high ESR, bad ground, or defective/open diode. Having two functionally
similar circuits should help.

Hmmm…. Maybe. I will check that.
Yes, having 2 would help immensely. That’s why I also asked Eric at Zentronics for his help, as he has a known good working one.

I was looking at the prod mod sheets and noticed the instructions and partial schematics seem to be correct. The diagrams showing how to make the mods do not match the instructions or schematics. If the positive board has been repaired/modded it is possible the wrong rework was done if done based on the diagrams.

On Fri, Jan 21, 2022 at 05:24 AM, <Zentronics42@gmail.com> wrote:

Interleaved.

On the fast rise and fast fall edges and waves forms on this unit as well as
the PG506 are not symmetric.

Yes, but probably not by that much like on mine. They are TOTALLY different.

I got burned because I though fast rise was
ground to +1V its not that is the fast fall output. So I was using the wrong
output and was wondering why the transition was slow.

I’m sorry, I don’t see what you mean. What do you mean “the wrong input”?

Your fast fall looks
healthy.

At least that…

Fast rise. My gut is telling me there is leaking silicon. But I could

be wrong. One of the tings that is bugging me is it cant sustain ground the
voltage decays back towards -1V.

Yeah, maybe…. But which one…. I hope it’s not the GaAs diodes….

Zen

On Fri, Jan 21, 2022 at 05:38 AM, tgerbic wrote:

I was looking at the prod mod sheets and noticed the instructions and partial
schematics seem to be correct. The diagrams showing how to make the mods do
not match the instructions or schematics. If the positive board has been
repaired/modded it is possible the wrong rework was done if done based on the
diagrams.

I’ve been inside this unit quite a lot. I don’t recall any modifications to the outputs. I haven’t touched them myself, and they do seem pretty stock.
I didn’t want to make any modifications to these outputs without making sure that was absolutely necessary.

I assume you’re referring to the silicon diode mod, right?

I flipped around Q103 and Q124. Everything seems to be quite normal now for the fast + square wave.
The fast - square wave is also the same as before. Maybe just removing and reseating the transistor was all that was needed. I’m going to leave them reversed as it seems to be ok now. I don’t think I need to touch anything.
Several latest pictures here:
https://groups.io/g/TekScopes/album?id=271865

If you have any comments or suggestions, please fell free to share.

I’d like to say thank you to Bob Albert, David Templeton, Zentronics42, and tgerbic for their help. IO really appreciate it.