Let’s keep this series going.
In the last episode, our suspect was A2U1 which is HP part number 1826-0065. That’s the way the IC is marked and that is also what is written in the service manual. But I am lucky as the service manual adds that A2U1 is an “IC 311 COMPARATOR 8-DIP-P” and I already have them in my spare components.
So, is A2U1 bad? Well yes, it is.
In goes another 311, out go A2CR6 and A2CR7 (to be fair one of them wasn’t broken before my repair attempts), in go all the pass transistors and two zeners I had laying around and all the power supply voltages are now close enough to their right value.
Now I have to replace A2CR6 and A2CR7 which are 1N5340B (and not as the service manual prints 1N53408). I think that I will add them to my next order so it will be some weeks before this series resume. Maybe I will also order some replacement capacitor but all the ones that I tested measure fine.
When the power supply will be properly rewired and tested it will be time to see if it took with it other boards when it failed.