[AMRadio] Muting the R390 on transmit

Grant Youngman nq5t at tx.rr.com
Wed Dec 2 14:00:43 EST 2009

I didn't assume it was just a silent "A" and it does make a difference :-)

In the R-390, the break-in relay is K-602 and the Squelch relay is K-601.   In the R-390A the Break-in relay is K-601 an there is no Squelch relay.  There are differences in how muting is effected in the two radios as well, since the R-390A does not use an interstage transformer to drive the line and local amps.  But the general notion of getting control voltage to the break-in relay is similar.


On Dec 2, 2009, at 12:31 PM, rbethman wrote:

> The cited References are for the R-390A.
> John, which is it you have?
> *IF* it is the R-390A, then the break-in relay *IS* K-601 in the AF Module.
> Bob - N0DGN
> Grant Youngman wrote:
>> 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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