Conclusion...
...at least to this point...
We can only guess so much with the Information we have, but for best troubleshooting technique, a lot can be determined by the operation of the front controls.
Meter lite - even work? Might mean a power failure - not just burned out.
Dimmer function - Meter lite and channel display show Bright/Dim?
No PA - Mic circuit ... but there's more.
RX and TX modes? No receive but hiss, does it TX red? If no red light then power supply failure nearly certain...regarding TX Switch or Regulator (TR21 or TR23 respectively)
Any RX at all change channel - any RX at all? May be a SECONDARY 5 volt power supply failure affecting PLL and Voice Lock controls would confirm this by testing for voltages on RX to ground from pot terminals.
I guess your Voice Lock works...
So the above - we're thinking that since you say...
You have Receiver in patient - RX now works.
Have Speaker for RX,
You change the channel you have RX for that channel...
Just no PA.
Indicates Mic Gain Amp failed...
Because - you have 4 watts TX...means...
Shows PLL has power,
Because your TX light turns RED...
We presume everything else...is ok...
So, for the issue of "remove Thy Limiter" - locate AMC Sense cap, see above, and or D11 - see photos above...and lift 1 leg of diode - does Audio Return? Then the problem is in the LIMITER side of the mic amp...
Proceed at you own risk...
See Above...
Hope this helps
Regards!
:+> Andy <+:
