Hello there. New member here. I recently bought an HP 54501A for cheap, knowing that the NVRAM issue was what was causing the self-test failures. I replaced the Dallas chip with genuine item from Mouser. The unit passes all self tests and I have gone through several of the training exercises detailed in the Quick Start guide. Everything works exactly as it should - except......
The vertical axis seems to have a small amount of ripple in the signal. All voltages whether sine or square or DC all "wiggle" for lack of a better word. If I tell the scope to display real time voltage, the number is not steady, but jumping all around by several tenths. The background video - scales, menus, labels, etc are all rock steady, so this is not a CRT issue. It is only measured signals and it does this whether using the rear DC or AC reference ports, or when using an external signal generated by a function generator.
I was wondering if anyone has any suggestions of where to start? I'm guessing it is possibly a reference voltage that is not regulated properly? Would this likely be a power supply issue or main board? I do not have a schematic, but do have the service manual which does provide information on some calibration.
Thanks in advance for any advice!