Re: Problems with recently un-stored 549

Kevin Wood G7BCS

The "bloom" would normally result in the trace getting larger due to
reduced HV potential as the supply dies, not smaller as you report.

It would certainly be worth watching the screen voltage for any runaway.

The other symptom that is obvious when the HV supply is out of regulation
is that the display "blooms" (gets larger) as you turn up the intensity
and draw more current from it.


I think we're talking to the same end from different directions here. My
initial description of the fade-out did not include the "bloom" because at
that time I did not notice it, it happens very quickly. However, after
discovering TekScopes and on further monitoring it's quite apparent -- a
case of initially not knowing what to expect or what is relevant. As I
said initially, I'm not well-versed in this tech, so TekScopes has been a
great education in that regard.

I've found the oscillation circuit and the V800/6GF5 tube's screen voltage
on the 549 schematics, now to track down a test point. Tom Browne's
recollection of the screen voltage was spot on -- +23V

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