Greetings all,
I'm looking for this groups sage advice.
A friend dropped off his Alpha-78 that was converted to a pair of
3CX800's along with adding the PWD transformer P/N "Alpha 76A-2. In CW mode
the amp powers up and works. When I hit the SSB button, I hear the HV relay
try to switch and there are sounds of arcing and then of course the fuse
pops. This is all within a few hundred milliseconds of pressing the SSB
switch.
I can't find the smoking gun here. No real evidence of what is failing
or flashing over. I took apart the filter cap stack, looing for arcing pits
or carbon scoring. I did not see any evidence of things punching down
through the rubber insulator to the chassis. Then I carefully unwound the
HV cable harness looking for a pinch that might have punched through and
found nothing. Then I also disconnected the B+ wire that goes over to the
RF deck and no change.
For grins I measured the voltage across wach cap in CW mode and 5 of the
6 had equal drops of about 290V, but one of them was lower ~245V. Not sure
what it means but is a data point.
Has anyone seen something like this before. Comments and suggestions on
what to look at next would be most appreciated.
Thanks in advance.
73's MIke K9MK/5
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|