My best Commodore monitor, the 1084, went belly-up on me today. It's been
showing sings of trouble for quite a while, but this time it finally failed
over.
Nothing worse than an intermittent..
Symptom was a little non-intuitive. The video would go out, randomly, and
all at once - like flipping a light switch. But when it would return, it
returned more slowly - it faded in, as if the CRT heater were warming-up.
Now, if the heater were losing power, why wouldn't it fade +out+ as well?
But I checked, and the heater was definitely off - no glow, no voltage at
the heater pins 9 & 10.
Anyway, it turns out that this is one of those sets that draws its heater
supply from a second winding on the HV flyback transformer. After some
inspection of the board, I found that one of the flyback's soldered
mounting pins had cracked at the joint, causing an intermittent connection.
This was the cause of both symptoms - a quick cut-out of the video when the
HV disappeared, and the slower fade-in as the connection re-made and the
heater warmup lagged the HV rise.