Hello!
@Sandy: Problems are more or less everywhere the same obviously.
Even though I don't use the set very often it became defective in the meantime. The vertical oscillator ran much too slow. Further loud hum came out of the speakers even though the smoothing electrolytics are replaced with new caps.
A least I was able to repair both faults. I replaced the oscillator tube and some drifted high value resistors with old but well measured resistors of better quality. One of the old resistors should have 1 MOhm and measured more than 5MOhm. The audio hum dissapeared after cleaning the contacts of the socket of the audio driver tube.
It seems this set will never work really reliable
I used this opportunity to add a further fuse in the DC circuit to avoid possible damage in case of a short circuit. I took the fuse holder from a junk set also from 1956 I parted out some time ago. I think it fits quite well in my opinion.
Greetings Josef