Sencore VA-48 issue

[DavGoodlin]

I was debating opening it up to fix this or just asking if anyone else had this issue?.
This unit works well for the color bars, but when you switch to crosshatch or dots, you see the pattern for a second, then it goes blank. I suspect something on the 500 board is going thermal and may try freezing some ICs

After using the color bars for 30 minutes or so, they disappear also. I have the schematic book and parts list, so I can easily locate and replace whats bad. I will start by checking the power supply but would appreciate any helpful hints- thanks!

[Findm-Keepm]

Dave, check the power supply caps for high ESR and also all of the decoupling electrolytics on all the other boards. I helped restore a VA48 for a friend a few years back. Sadly, he's now about blind with macular degeneration, so it sits. Bad caps cause high ripple that interferes with the counter circuits they use for division in the VA48 - that's how they get the lines for crosshatch, etc. I shotgunned the caps, but later checked a few and realized I was dead on in getting them out. Some values had to be subbed with slightly higher values of capacity and voltage, IIRC. Standard values in the 70's aren't standard now, so subs were the way to go (3000uf got a 3300, etc.)

Cheers,