[GreenKeys] OT: Need help to T-Shoot this Tek 485 scope

[drlegendre .]

Hope this is OK..

I'm trying to fix a Tek 485 scope that has lost the ability to control the
trace brightness aka beam current. When it arrived, it had a power supply
defect (shorted cap in +15) which I traced & repaired. But after running
for 3-4hrs in shakedown, the traces lit up like the sun and cannot be
controlled.

I have replaced the diodes in the grid DC restorer circuit with 1N4007
(equiv). No joy.

Can anyone offer assistance? Right now, what I really +need to know+ is
what voltage difference should I see between g1 and cathode? I read about
-9V, but I'd think that's awfully low for a tube with 18K of acceleration.
Would expect more like -40 to -50V.

Replies off-list if that's appropriate. Thanks!
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