[MRCA] Update on the PRC-47 no transmit problem.

[James Green]

I just made a small breakthrough. So far everything I have checked and compared between working and not working radios has been non-conclusive until today. Yesterday I got to the point where the manual said to look for the 500KHz carrier signal. It was not there in the non working radio. The manual said check the VOX relay K4. I did and K4 is not getting the required 27VDC to the coil to engage. Neither is K6. However, K1 and the T/R relay are doing fine. Today I checked the working radio and all of the above relays engage in transmit. Now all I have to do is track down what would prevent voltage from getting to K4 & K6 but not K1 and the T/R Relay.

More info:
I just re-checked a couple things and K4 is now operational. K6 however still is not responding. The coils of all the operational relays terminate at ground. K6 does not. I checked and K6 coil high side is getting 27VDC to ground, but not to it's low side. The low side connects to J11 pin 3. This goes up into the oscillator control module. I removed the oscillator control modules of the working and non working radios and put the one from the working radio into the non working radio. Still no joy. The problem likely is not oscillator control module related.

I'm stumped. I'll keep staring at the schematic perhaps something will jump out at me.