bz wrote in
98.139:

The saga continues....

Removing the plug in module DID clear the 100 ohm 'short' to ground on
the 100 volt line.

Swapping tubes did NOT fix the -150 volt supply however.
It only measures -131 volts (after several minutes of 'post hv turn
on' warm up). It drifts much more during the warm up than the -150
volt adjustment pot will swing to voltage. In fact I see very little
change as I adjust the pot.

The 100 volt supply is putting out about 130 volts and the rest of the
supplies look about normal (have not checked the HT supply to the CRT.
I wonder if it being too high could cause all my symptoms).

Measured the current out of the -150 and 100 volt supplies (across the
5 and 10 ohm series resistors). ~.95 volts /5 ohms = 190 ma for the
-150 supply
~1.4 volts/10 ohm = 140 ma for the 100 volt supply. I am assuming that
those values are not unusual. I have not looked at ripple, etc., yet.

Looks like I am going to have to measure voltages at several points
and try to make sense of any patterns that emerge.







in troubleshooting those old tube scopes,I used to keep a few electrolytic
caps with clip leads to bridge the PS electrolytics,when I had a low
supply.

--
Jim Yanik
jyanik
at
kua.net