When you get back to this. Check the Mic GAIN - you can see if it works from the front panel Mic jack.
Locate Pin 1 and 2 and use a DVM to check for resistance.
Mic Gain (Dynamike) all the way up - will show about 2K to 1K resistance BETWEEN Pins 2 and 1 - HAS TO BE PINS 2 and 1 for this check, Case ground is insulated from chassis and power return (Foil board ground) so you would not get proper readings - if any...(near infinite)
Turn Dynamike all the way down - Pin 2 to 1 would show nearly 15~25 ohms (near dead short condition) for the Dynamike control SHUNTS Mic power to ground.
Pin 2 is Mic Audio Pin into the radio - and is controlled by the Dynamike control.
Pin 1 is Shield, Ground for TX switch Pin 3 and Speaker Return Ground Pin 4. Pin 2 is audio in...does not show connection (ohmic resistance) to any other pin except for Pin 1.
Ok, back to Mic amp - C70 is the "sample cap" that send energy from the Audio and B+ line that goes to Final and Driver - to the Limiter TR14 - So if limiter or any parts on it are not working right, the Limiter may engage all the time. For troubleshooting - remove TR14 unsolder it - does audio return?...if so, the issue is with the limiter circuit.
TR14 is a 2SA733 a PNP
Leave TR14 out for next test...
Locate C94, C90 and C148 - C94 uses Regulated TR17 voltage - via R111 per schematic. So when checking - use a dummy load on the antenna jack and plug in a known good mic into the mic jack and set up DVM to check for voltages on both sides of R111 - one side will have 8V or so DC on TX, but drops on RX - other side of R111 should be about 6V on TX and nearly 0 on RX. TR16 (TX Switch) feeds power to the Mic amp on TX. BUT TR16 TAPS off of TR17 to power itself and send 8V TX power to where it needs to go - including the Pre-driver.
If Mic amp side of R111 stays below 4 volts on TX and R111's other side shows 8V - Mic amp section is in trouble. IF R111 stays at 8V on both sides, possible bad soldering or that TR13 is blown and needs to be replaced - 2SA945 - NPN.
If R111 Mic amp side is too low 4.5V or less, you have shorted parts or bad soldering.
If it goes to zero volts and stays there - pull C94 and re-check - if voltage (6Volts or so) returns - replace C94.
If TX voltage is too low - locate R44 may be labeled as L44 and a molded inductor is mounted there instead - pull R44 (or L44 - as applicable) part and check for voltage again - no change - possible TR17 and support are faulty. Else if voltage returns possible that Pre Driver is bad or area leading to it, including L14 are suspect - pull part and recheck - replace pre-driver if needed..
