Total posts : 45366
The measurements help. An op amp operating within its capabilities will have almost zero volts between the + and – inputs. This is not the case for pins 2 and 3 in your circuit.
The voltages which do not look normal are:
LM358 (U1A) pins 2 and 3. The voltage on pin 1 should be about 8V but is .18V possibly because the voltage on pin 2 is more positive than that on pin 3.
TIP31 Collector (should be the supply voltage around 13V)
TIP31 base to emitter voltage appears normal for a darlington but because the voltage on U1A pin 1 is .18V the base voltage should be 0V. This suggests that Q8 is defective or that you confused Q9 with Q3 for your measurements.
With the voltage at TIP31 (Q9) emitter at .12V you cannot be getting “full power” and should be getting no RF output. Did you measure the voltage on Q3 by mistake?
The audio is not passing through U1A because it is not operating in its linear region.
With the voltages you measured it should not be possible to have .12V on TIP31 emitter and .18V on U1A pin 1 and have 5.75 volts on U1A pin 2. Either U1 is defective or there is a solder bridge or other problem with the printed circuit board. Are you sure the LM358 is not installed backwards?
The voltage at the TIP31 (Q9) collector puzzles me since it is connected to the + supply as is U1A pin 8 and these voltages should be the same. Check your readings again on these two points. The TIP31 should not be hot with the voltages given unless the emitter circuit is shorted to ground somewhere. What voltage to you measure from the junction of R5 and R34 to ground?
It is possible that there is more than one problem but the problem appears to be with the U1A circuit. I would replace the LM358 and Q8. It is possible that the “new” LM358 you installed is defective or was damaged.
Hope this helps. If you can give more information I will try to help.