Well today, after running the cathodes hot for a day or so, with with B+
disconnected in order to degas/getter the trio of 8874s in a
an Alpha 76. Today I put it together for a smoke/bang test with an exciter and
Dummy load.
It was operational when last used, but that was perhaps 5-10 years ago. Cold
storage since.
I ran the PS and tubes (with B+ plate caps disconnected) up slowly to reform
the capacitor bank if that was necessary.
HV meter indicates nominal low and high values (CW-SSB) of B+
Now, with the Amp ready for RF drive test, I discover that the time delay relay
for application of B+ after warmup is not working. The red meter lights stay
red, and don't go to blue after the minute warmup. (or at all) A UJT Timer
with two xistors, and a Cap, circuit on the same board, and uncomfortably close
to the B+ caps, etc. So, I prefer not to probe that board for low volts while
B+ lurks < 1 inch away on the same board.
See photo:
https://cid-2eb5c45df634a712.photos.live.com/play.aspx/ALPHA%2076A%20Amplifier?ref=1
Also Someone who is very familiar with the Amp, scroll back in the photos to
the bandswitch and Tank coil straps to tell me whether the 10M tap is active.
No 10M band silk screen on front panel, but the B Switch knob goes an extra
notch beyond 21 mhz.
So, I am thinking how to approach, without big bangs, Sparks, dead bodies in
the shop, or smoke while servicing.... Anyone know a history of HV delay
circuits on the Alpha?
Best Regards,
Pat Barthelow AA6EG apolloeme@gmail.com
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