tds 744a screen flickering

[durresaku13]

tektronix   tds744a
anyone can help to understand what is the problem with the screen flickering after 7-10 min that is turned on?
thank you all.

[TERRA Operative]

Probably old capacitors on the CRT board are getting upset when they warm up.

What type of flickering is it? Can you upload a video to youtube and link it here?

[durresaku13]

thank you for your time.
here is the link of a short video for the tds744a flickering screen. when i change the colors through the color menu,  flickering  either intensifies or slows down to only one of the shutter color blue or red or green depends on the colors i change on the screen. its very annoying. some times this problems starts within 2 min, other times within 10 min.
thank you again.
https://youtube.com/shorts/W6rLuFVFOtw

[m k]

Can you show a test picture where large area is colored?

[nctnico]

Interesting problem. It looks like the shutters are out of sync with the vertical retrace (assuming the video shows the same visual effect as the scope). Given it is heat related, it could be as simple as a bad contact. I'd start with reseating the connectors on the board with logic in the CRT / display module. IIRC there is also an EPROM on the board. Reseat this as well. Make sure to take ESD precautions.

If that doesn't help, get some freeze spray. This typically helps to find / locate heat related problems.

[TERRA Operative]

Yeah, I'd reseat connectors as nctnico mentioned, and take a close look at the vertical board mounted on the CRT driver board assembly, it is the shutter driver.
Might be a bad capacitor or something.