Re: Tektronix 2246 flickering screen, ch2 not working.


grusus@...
 

I made some photos of traces.
V/div and time base like in service manual.
6A: https://photos.app.goo.gl/3JPDuHeFoFpadMsQA
6B: https://photos.app.goo.gl/Qw58roiYCzeScTVQ7
When I go from A sweep to B sweep I see this:
https://photos.app.goo.gl/yyLausR5frKo5FMv5
Trace is on left half of screen.(that was from time I get the scope)
When I turn sec/div 1 position ccw i get this:
https://photos.app.goo.gl/aiXmWaZn2VDtXKoc9
6B then is: https://photos.app.goo.gl/nkmv5ZFTY3fGdKAP9
Turn sec/div back one position cw I get this:
https://photos.app.goo.gl/UUfgEAHQD5jTt4tUA
6B Looks this: https://photos.app.goo.gl/JAdj8BHENuPWcrm26
I think that is not a normal behaviour.

6C: https://photos.app.goo.gl/zTbj4Fm3LGL17TYu7
6D: https://photos.app.goo.gl/UNecEuXAGtQXzjSR7
6E: https://photos.app.goo.gl/yiykE79w3CnfjKah9
6F: https://photos.app.goo.gl/4Z1engjbXPfp5hzM8
6G: https://photos.app.goo.gl/RjmTHAermev4fa9r6
6H: https://photos.app.goo.gl/XJtnovY3V2vqp9TV7
6I: https://photos.app.goo.gl/NaW8gZc32HAAKFuX8

Scope behaves like this (previous video was before recap):
https://photos.app.goo.gl/GMHjh4wK8cWLfcCc9

I am wondering why holdoff is influenciing traces the way they cuts, and also readouts flickers more or less with different position of holdoff. Also scale ilumination has influence on overall flicker.
Other thing I noticed: There should be grid with dots all over crt when readout is turned on (seen on others video). Here they are present but they are jumping/floating around from left to right very quick.

Other thing is Pin1 of U 802 is Readout horizontal input and looks like this:
https://photos.app.goo.gl/TYZogpEe5RccrkTXA

Output of U801A Pin1 is:
https://photos.app.goo.gl/tDQGWUuNRZYTp7jMA
https://photos.app.goo.gl/aWBX1pYvkmcbiNAq8

I am wondering if there is some timing issue, considering strange behavior in b sweep and no stable matrix of dots with readout. Maybe it is influencing also a sweep and overall performance. Where to look for it?
As I said, I am noob in scope reapirs, trying to learn from people who are much better than me. This is for my personal use. Any help like "look in baseline stabilizer" or similar will be apreciated.
Many can say buy a working scope. There are two things: Money (good scopes cost a lot) and It is nice to use equipement that you have reapired yourself.:-)

Also scope behaves very odd when it is cold. It must run for 5 minutes and is operational as on video in this post. For first 5 minutes uncal are blinking, brightness of crt varies. and eventualy it gets as bright as it shold be. There are random brights up during first 5 minutes.

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