I'm a newbie to this forum, but I collect antique radios and I have been messing with electronics since a kid 50 years ago. Looking for some help on try to find this problem. A little history of the scope. Got it from ebay for $30 including the shipping. The high 56V winding of the transformer was open. I left that transformer to supply all the other voltages and bought a 56V transformer that I put on this thing. I have tested all the voltages out of the power board and they are pretty close and well within the specs from the manual.
I have followed to schematics and scoped almost every point where they show a waveform and all are very close, within 4% of what is shown. When the input selector is set to GND and time/div set to 1ms the line wobbles up and down, it doesn't change with the volts/div knob. It is the same for both channels. It is the same with ADD setting too. As I said, I checked voltages and waveforms for both input amps, the channel selector and the vertical controller board. All seem fine.
I have the suspicion that it could be power supply related, does anyone have other ideas before I go and start changing all the caps?