[Premium-Rx] Still struggeling with my RACAL RA 1792

[Heinz Breuer]

Hello Group,

I am still struggling with my RACAL RA 1792 which was dormant on the 
shelf for a long time. It showed errors in BITE 10, BITE 11 and BITE 15.
BITE 10 showed me a problem with the EAROM IC 13 and 14, sometimes both, 
sometimes just one or the other. Voltages were all ok but I finally 
found the culprit with the ESR meter. The tantalum capacitor on the -12V 
supply rail next to the 7912 voltage regulator showed a very high ESR.

I also had a BITE 15 error with variable BFO for a couple days but 
somehow it is gone now. It stopped in the kHz region, sometimes at 2 
sometimes at 5 or 6. I can't see how the defective tantalum cap on the 
EAROM supply should have had any effect here.


I still face a BITE 11 error, this is varactor diode ref out of range 
and relates to the A8 board 2nd LO/BFO Synthesizer.
Any advice what might help?

Another problem is the AM key. It doesn't make contact any longer. If I 
hold it down and power up it is not shown as sticking. I tried some Caig 
Deoxit but can't really get into the key. Last resort would be a new 
key. Are these still available? I seem to recall these keys used in 
early IBM PC keyboards but trashed these keyboard decades ago.

vy 73 Heinz DH2FA, KM5VT