I have an issue with the Intensity control not having much effect on brightness, then all traces fade out after 10 minutes.

The schematic shows a circuit that controls bias on the CRT via R828, a 1 Meg.

Could it be as easy as one bad resistor?

205683

The image is really hard to read. Are you referring to the resistor in series with the intensity control?

Also, have you checked the three rectifier tubes?

Better images here:

https://w140.com/tekwiki/wiki/516

I would suspect the 3 caps near the intensity pot. :scratch2:

jr

Thanks!. I will try the 5642's, I have a spare as well.