If C68 was open, or if C69 was shorted, same thing. ![]() If TR18 was shorted to ground then all your audio would be shunted and you would have no modulation out. This is very much an oversimplification but i want you to know what the parts are doing. This has the effect of cancelling out the "overmodulation" while allowing the audio through at the preset level. TR18 is your AMC control and is taking a sample of your audio and feeding back anything over 100% (or wherever you have VR4 set) out of phase back into your audio path. The other end of R122 connects to the collector of TR18, and also to C68 and C69. If R122 is open, your mic audio would not move past this point. If C74 shorted, then it will pull all your mic audio to ground. one of the outer pins of this control goes to PC board ground, and the other outer pin connects to C74 and R122. ![]() from there it connects to the center pin of the DYNAMIKE control. Your mic audio comes in on pin 2 of the mic jack. We are going to follow your transmit audio path from the mic to the driver and final transistors. You say that you have good receive, and that the radio transmits a 5 watt carrier. this means i have to assume that you are 100% certain that the mic you plug into the radio works 100% of the time on another radio or a mic tester that you can hear yourself talk on. ![]() So, you said you have tried different microphones. Ok, so i have to assume a couple of things based on what you have posted here, and if those things turn out not to be the case, then everything else i post will be meaningless.
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