Hello TVtech!
Following my history of posts about electronic projects that refuse to work or explode, I see why you suspect that I have no idea of what I'm doing. Usually its the case, but not this time.
I tried using the compensation circuitry included on the probe to make the test wave look like the manual's photo, but it seems to be inoperative. I hope to replace the probes as soon as I get some money.
Now, I know that electrolytic capacitor faults would be more associated to situations were the oscilloscope totally refuses to turn on (i.e. the HV section is dead). But I tough that checking the capacitors is not a totally bad idea for two reasons:
First, this oscilloscope's manual empathizes on the necessity of high quality mains for feeding the unit, to avoid funky readings or blowing up the whole thing. Maybe the manufacturer knew that their mains filtering was not very good?
And second, after spending some nights reading this
vintage electronics site (by the way very good one) most of the problems the author finds are related to old electrolytics.
Start changing capacitors on the dark? definitely not a good idea. But at least a good reason to build the ESR meter project, don't you think?