Hmm. I'm afraid I did damage something.
It seems that I accidently shorted +100 V and -150 V (some lead bent and came in contact with its neighbour without me noticing), LR149 (in the time-base generator section) started to smoke. Now when I power the scope there's a high frequency whine somewhere (near the CRT high voltage generator, it seems) and the -150V shows a 100 kHz 7 Vpp fully rectified sine wave superimposed with a 100 Hz ripple.
Besides, the trace now only spans 6 horizontal divisions.
I forgot to mention that I'm in France, where the electric network frequency is 50 Hz and not 60 Hz like in the US. Hence the fully rectified 100 Hz ripple.
De : TekScopes@groups.io <TekScopes@groups.io> de la part de Peter H <firstname.lastname@example.org>
Envoyé : samedi 4 avril 2020 15:57
À : TekScopes@groups.io <TekScopes@groups.io>
Objet : Re: [TekScopes] 531A power supply ripple
all regulated voltages are referenced to the -150V supply, make sure this is clean and correct first.