Jason Buchanan <[EMAIL PROTECTED]> made an utterance to the drakelist gang
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hi,
I have an L4 with its original power supply. Been working fine for a
long time.
Today, I turn it on and after a few minutes there is a large pop and
blue spark from near the HV interlock, or located behind the rear tube.
The .82 ohm resistor fried - I replaced it with a new one and carefully
inspected here and there in the amplifier cabinet. I couldn't find
anything that burned near the interlock.
I powered it back on in CW low voltage position and the plate voltage
reads around 1300V. On SSB it reads around 2000V, maybe a little less.
That was all the experimentation I wished to try. I opened the L4-PS
and looked around but can't find anything on the top side that looks
burned or stressed.
The thing I noticed that was peculiar was that when I powered the L4
off, the plate voltage would begin to decrease as expected, but then
ROSE about 200 volts and then slowly decreased again as expected. When
I took the amplifier cover off there was still a bit of voltage in the
HV supply, around 150V on the meter. I used a pair of alligator clips
to ground the cabinet to the top of the plate choke and then removed the
clips - what was odd was that the voltage rose up to about 100V - when I
grounded it the meter read 0 again. When I removed the clip it rose to
about 50V. Finally I put the clip on and left it on and it finally
stayed at 0 with the clips off.
Has anyone seen this before? Any idea what is wrong... and what I can
do to repair it?
73 Jason N1SU
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