[Central-Electronics] CE 20A 9 MHz Oscillator
Paul Christensen
w9ac at arrl.net
Sun Jun 16 08:42:27 EDT 2019
I own two CE 20A transmitters. While repairing a 458 VFO, I noticed that
the 9 MHz oscillator was gradually failing on the older 20A. I traced it to
a cracked 560 ohm B+ resistor, R20. Replacing it restored the 9 MHz master
oscillator.
While making the repair, I noted that the 47K screen resistor (R72) is fed
direct from the 300V B+ supply and is not tied to the cold end of the R20.
The schematic shows what seems to me as being the right way to configure the
screen where if R20 opens to the plate, then voltage to the screen also
opens. In the current configuration, if R20 opens, voltage is still
supplied to the screen grid and in effect becomes the plate.
Both 20A transmitters are wired the same way. Possibly a factory wiring
error? Before I make the change to reflect the schematic, can anyone tell
me if I'm mistaken in my belief?
Paul, W9AC
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