On 7/14/2021 5:38 PM, Charlie wrote:

Greetings,

I hope this message finds everyone well. I am calling on anyone who would like to offer some tips and/ or assistance. I am a new(er) member and thus far I have been following along and using the search function from time to time to get some direction on my little project. It has been a little slow going since there is so much information on here to sift through, but I am hoping someone can give me a kick in the right direction. I already know I will greatly appreciate it. Please excuse any mistakes and simplifications. I am not a professional electrical engineer, but a hobbyist with a fair amount of formal EE education.

Here is a little background...I purchased two of these scopes, one was supposed to be in good working order, one was for parts. The "good" scope has the GPIB option. On start up of the "good" scope I keep seeing this image on the CRT

https://photos.app.goo.gl/GwUdDxu25jh4APwZ6
A few times the unit would show the traces and I could get into the setup menus. This was unpredictable and I would say 90% of the time the scope would lock up on the screen shown above. When I was able to to see the traces and get into the menus the cursor knob was wildly erratic. From what I have read this is pretty common issue with the cursor control. Aside from these issues the scope seemed to function OK. I should note that I have not done any other testing on this scope. Currently the scope is almost completely dissembled, A1-A6 boards are still mounted to the frame.

As of now, my intentions are the following, with any questions/ comments below;

1. Replace line filtering caps (A6 caps and A1C904)

2. Replace all electrolytic caps, particularly all power supply caps

Do I need to worry about the slew of tantalums throughout the scope? Some are conformally coated, some are hermetically sealed (relatively expensive). I have put together a spreadsheet/ BOM with replacements. I will post a link if someone can double check my choices

3. Disassemble and carefully clean the dual inline continuous rotation potentiometer (A24R9412)

I haven't found any replacements (no surprise). I plan on characterizing the operation of the pot to get an idea of its operation so I might be able to design a replacement. My question is, how do these operate to form the signal for the A11A1U6106 MUX? I have found one gentleman online (I believe he is a member of this group) who at one time made a custom replacement for these using a microcontroller an encoder and a digital potentiometer, but at this time does not plan on making another batch. He did however give some pointers on disassembling and cleaning the pot.

4. Replace the extended memory battery

I remember seeing somewhere on this forum that this battery is used to protect waveform data, not calibration data. Is this correct?

5. Startup and test the scope

Aside from what I have planned, are there any bugs I need to look for, or are there any other preventative maintancence items I should plan on doing?

Again, I truly appreciate any assistance offered. I have been very excited to get this scope back to operating condition.

Regards,

Charlie

I have a big bunch of 22/21A /30/32.

( Big #1) replace the line filter!

(2) Check the resisters in the focus string.

FWIW I have never really needed to replace any of the filter caps.

 Bert