[CQ-Contest] AMECO PT-3 Component value?

[Martin Ellis]

Good morning to the Contest group.

I experienced a failure of my AMECO PT-3 external preamp while
operating on 10m in the WPX Phone contest.

The unit seemed to be switching properly from RX to TX,
but it lost all output.  Using the In/Out switch I was able
to complete the contest. 

Tracing thru the circuit I find the fault is an open resistor
reference R12.  It appears that if RF from the transmitter
enters the preamp unit, it is dissipated in R12 (which is
connected to back to back diodes to ground).

My circuit diagram has no component values, and the resistor
is so damaged I cannot read the colors, or measure it. 

Can someone advise the value and size of R12?

Thanks, 

Martin ZL1ANJ

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