Repair servodrive yaskawa CACR

Hi everyone,
I’m working on a Yaskawa CACR-SR (BE1 series) servo drive. In general it works, but from time to time I randomly get A20 or A60 errors.

I have two identical drives, and I’ve already narrowed the issue down to the specific board shown in the photo. I was planning to replace all the electrolytic capacitors and also the film ones (I’ll probably do that anyway, given their age), but I also noticed component D20, which looks burned/blackened and has no readable marking.

I’m not an electronics engineer, but I’m quite good at soldering and I have a multimeter, so I can take measurements if needed. I’d really like to repair this drive because I have a milling machine that I only use as a hobby, and I simply can’t afford a new servo drive since I’m still young.

Could someone please help me identify exactly what D20 is (diode type and value), or point me to other likely components that could be causing these errors?

I wrote on this forum because I saw that in another topic an engineer had the same problem as me, but since it is an old topic I thought it was better to open a new one

Thanks a lot in advance for any help!
       

I think film caps are usually ok.

You can probably get away with all the caps as they are as filter caps are usually oversized, meaning the drive should function fine, even if the caps have degraded, though I suppose it couldn't hurt.

I'm typing this on a keyboard which I accidentally plugged into reverse voltage (stupid Apple decided to use an identical connector, but changed the pinout); the chip got hot, I smelled "magic smoke", yet the keyboard somehow continues to function without any issue.

Burnt ≠ broken, though it's certainly not optimal.

Those photos are very clear and high resolution.

I can see the board better than I could with my own eyes.

Could you post some pictures of the non-broken board (so we can see what it should look like)?

  Yes of course This Is the okay board 

The bad board also has corrosion around CN7.

Perhaps the pasty-looking stuff on the transistors on the good drive is solder paste?

Maybe the working drive was already repaired (indicating a weak point at that location).

I understand your observations. Honestly, I don't have any way of knowing if the working drive has been repaired before, but it's a definite possibility, especially considering it could be up to 30 years old!
​Regarding the corrosion near connector CN7, it's hard to say for certain if it's due to a cold solder joint or other factors. Furthermore, the pasty substance on the transistors above could indeed be solder flux (residue from the assembly process or a previous repair), or it could be liquid leakage from the nearby electrolytic capacitors, which would indicate another potential issue. Both hypotheses are plausible on electronic boards of that age.

Agreed.

A lot can happen in 30 years!

It's so difficult to know for certain what the cause of the problem is.

Obviously, those burnt components are not good, but could be unrelelated to the specific issue you are experiencing.