I have a HPS40 which worked fine for about 2 years until recently. All controls are all right still, but no matter which source is probed, it displays question marks only instead of digits. All I know that the scope has been treated well before the failure.
A quick investigation shows that there is no visible damage inside, LM2940 produces clean +5V output, and the electrolytes are supposed to be in a good working order. The measuring probe is not broken either. I see the input is decoupled through four GoodSky 5V relays (SIR-S4-105A). Can it be one of them? Any ideas are appreciated.
I’m also inclined to think that the damage has something to do with high voltage. Since the relays are 100V rated, they’re going to fail first. The other active components I’ve checked don’t seem to be dead. Unfortunately, I’m not able to return the scope for repair, and I prefer to fix this issue myself. If I succeed and the problem ever happens again, I’ll know what to do. VEL417, do you (or your repair guys) know any compatible replacements of good quality for those SIR-S4-105A?