Tek 2230 Repair and Maintenance


Charlie
 

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


Bert Haskins
 

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









 

Charlie,

Unless you have specific reason to suspect that capacitors are failed I would leave them alone (except for very specific cases: e.g. RIFA safety caps); "if it ain't broke, don't fix it!" In your case you don't seem to have any symptoms that indicate failed caps; the scope powers up and appears to function correctly, which means that the power supply is working correctly.

-- Jeff Dutky


Albert Otten
 

Hi Charlie,
My question is, how do these operate to form the signal for the A11A1U6106 MUX?
The cursor pot itself does nothing special. The wipers are wired to separate MUX input lines. My interpretation is that the processor does the job to find out the direction (and also speed?) of knob rotation based on changes in successive voltage readings.
On start up of the "good" scope I keep seeing this image on the CRT
https://photos.app.goo.gl/GwUdDxu25jh4APwZ6
You noticed perhaps that this is the display shown by ADV Funct -> Cal -> Box -> Run. Normally you would return from this by once more pressing AD Funct. But the scope is stuck and doesn't listen any more to buttons pressed?

Albert


Charlie
 

Bert, Jeff, and Albert, thank you for the response.

Bert, I am planning on replacing the line caps. Seems to be the No.1 item to address during my research. Definitely not leaving that out! I have also heard that I should check the resistors in the focus string, that is also definitely on my list of things to do.

Jeff, I can appreciate that adage in certain situations, but I know that this scope was used in a university setting which makes me wager that it has a significant amount of hours on it. Not so much it is worn out, the interior is actually fairly clean, but in my (somewhat limited) experience, replacing electrolytics are a good PM measure especially when there is a fair chance they have seen some use (and have reached what many consider a ripe age).

Albert, on the topic of the pot, that is what I am thinking as well. I just want to see what kind of signal the two pots together send to the MUX. In regards to the screen at power up, I was not aware that this a cal screen. When the scope powers on to that screen, no control input gets me past it.. It could be related to my cursor control? Have not gone that far yet. But since the cursor control is essentially useless as it stands, I bet it has something to do with it. The few times I had traces, the cursor was so erratic that it made the scope seem to have a mind of it's own. Hopefully a good cleaning can get it working for the time being.

Again, thank you everybody for the help. I really appreciate the time you are willing to share with me.