Tektronix tds510a Image expands, then tube shuts off

[jhalphen]

Hi to all,
Hi Devicemodder,

i watched your short video, operation looks OK. As you don't show the picture expansion & fade, it's hard to diagnose anything.

Questions:
does just the Windows computer content display disappear & screen stays lit or does the CRT brightness die?

In traditional TV, image expansion & decrease in brightness usually points to a dying EHT rectifier.
In the schematic you posted, EHT rectification seems to be included in the Flyback transformer (modern "split-diode" transformer technology).

To assess if the transformer is at fault (or not) additional data is needed:
- the schematic showing the CRT, its type & hopefully electrode voltage.

Something might be drifting & driving the CRT to cutoff, blanking the display.
How is the Tektronix VDU powered; own power supply, bench PSU,...?

Have test gear: multimeter, HV probe,...?

If possible, a new video showing the "expand & fade" fault,

For anyone interested, the TekTronix TDS-510A digital Scope service manual* (284 pages/4Mb) is on TekWiki:
https://w140.com/tekwiki/images/5/52/070-9704-02.pdf

*didn't see schematics.

TekTronix TDS-510A wiki main page:
https://w140.com/tekwiki/wiki/TDS510A

Best Regards
jhalphen
Paris/France