[AMRadio] Muting the R390 on transmit

Grant Youngman nq5t at tx.rr.com
Wed Dec 2 13:02:19 EST 2009

On Dec 2, 2009, at 10:46 AM, John King wrote:

> Thanks for the source of information, Jerry. I have looked at the schematic on the Y2K site and see relay 601, the break in relay. Now I must physically locate it and determine if the relay is indeed bad. I have 12.95 vac at terminal 9 on the terminal board  on rear of R390. 

Not sure of the age or condition of your 390, but you might also just try pulling and reseating P120/J620 on the audio chassis.  Among other stuff, this connector carries the operating voltage to the Break-in relay, K-602.  (K-601 is actually the squelch relay).  Both relays just ground the audio out from the AF amplifier V-601 through the interstage transformer T-601.

Pins 1 and 2 of P120 carry the control voltage to the relay.  You could measure the voltage there also, to make sure it's getting that far along when pin 9 of the rear connector strip is grounded.


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