I have 3 of this family scopes, one 54825A that is working fine, one scrap 54820A I use for parts and the other 54825A that has recently failed, the latter one displays a "Fine interpolator gain cal failed: Service is required" error and does not pass self test. This scope showed the same error 4-5 years ago and I replaced A/D part 1NB7-8353 from my scrap unit on one channel and it worked fine after that. This time around I can not recall how to narrow down and find the channel with broken A/D. I fear that just replacing the A/Ds one by one may damage the acquisition board.
How do I narrow down and find the faulty part?
Does replacing these A/Ds one by one damage the acquisition board?