Philips PM3050 reapair help

[chorazy3]

Recently acquired this Philips/Fluke PM3050 60 MHz scope. Unfortunately there is a problem with displaying. Displayed waveform is getting weaker from left to right where it tends to disappear. This problem is worse with lower frequencies, like <10kHz and when using timebase of more than 50us. It is almost not seen with freq of MHz whereas those of Hz range can barely be seen. Attached some pictures. What could be the reason of this ? Replaced allmost all electrolytic caps on all boards but it didn't help (only left those 4 latrgest can elcos in PSU board). Central spot does appears for a less than second when pressing xdefl mod then it disappears.

Strange thing is that problem disappears when feeding both channels from generator and switching to chop Mode.

[chorazy3]

Running out of ideas guys (not an electronic). Replacing last four caps on psu board didn't help. Also replacing opto-coupler (CNX35=CNY17-1) on psu board didn't help. Checked diodes and they are ok. Also outgoing voltages going from psu to xyz amplfier, which is located on top of the crt, are ok. So i think there's no problem with psu or crt. Didn't check high voltage lines going from psu though.

This model is similar to PM3055 but it lacks DTB function.
Some pictures and SM from a previous thread:
https://www.eevblog.com/forum/repair/philips-pm3055-repair-and-teardown/

I am starting to think that there might be sth wrong with timebase board unit. In the SM there is an explanation about different blanking for chop mode and for lower sweep speeds:

[mzacharias]

Always rule out power supply problems first.

ALWAYS.

[didier7854]

Hello everybody.
First sorry foy my poor english.
Thank you for this very interesting site.
I just got a Philips PM3050 oscilloscope from a friend. This device has not worked for a long time and has been improperly stored. Upon powering up the 0.22uF capacitor at the input of the power supply exploded with an unpleasant odor.
I repair the power supply with the change of some capacitors. When not connected to other pcbs, the power supply provides the correct voltages on the X6003 connector. By reconnecting all pcbs, nothing lights up. After various tests, by disconnecting the flat connector X1009 from the "pcb attenuator", the device switches on normally with the control screen as well as the heating of the tube. The attenuator would therefore be the problem, maybe an excessive load on the supply? If you have any ideas or encountered this kind of problem it would help me because I am a little lost. Thank you so much. Didier

[alolkema]

Hi chorazy3, Have you ever found the issue? I am encountering the same issue, but on a pm3375 after recapping the whole scope.

Thank you in advance !!