HP54501A - Two channels don't working

[MiloszW]

Hi,
Fristly i want to apologize for my english - I'm from Poland.
I have a problem witch my oscilloscope HP54501A. Channels 3 and 4 don't working. On the screen you can see lines, when channels are on. Also regulation of offset don't working.
Channels 1 and 2 are working verry good.

[oz2cpu]

Utility - Self test

results ?

also look at the block diagrams, service manual is easy to google

go here:

https://www.manualslib.com/manual/1285851/Hp-54501a.html?page=67#manual

as you see ch1 ch2 works
and ch3 ch4 dont works, now looking at the blockdiagram, you know where to look and compare
ADC stuff and RAM and RAM handeling might be a good place to start,
also the ch3 ch4 analog parts might have a seperate powersupply, so start to check you get all ok analog from the front stages

[MiloszW]

Results of selftest.
ADC failed - but two channels are working...

[oz2cpu]

exactly.. goto manual, and check parts in the ADC, and its control signals
turn on all 4 channels and compare