Late to the party.? So from the sounds of it you have no modulation or very little in any mode.? SSB, AM, FM or data.? That should be rather easy to troubleshoot.? Just inject a audio signal (10mV at 1kHz) into the mic jack and signal trace the audio through the TX audio chain.? All you need is a oscilloscope or even a antique signal tracer will work.? Just follow the mic audio chain using the block diagram.
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Mikes Radio Repair
KC3OSD
Mike KC3OSD