I have been able to find out that it is RV9 (at least on most versions of PTBM121D4X based radios) that is for adjusting the SSB AGC in RX mode.
Most service manuals states that one should adjust RV9 to approx 2VDC on terminal point 14 (for example this service manual on page 50: www.cbtricks.com/pub/secret_cb/vol_19/g ... g48_51.pdf)
I have been looking at the schematics and the board itself and the only terminal point 14 I can find is the post that goes with a wire to the Local / DX switch. However, my radio, HyGain V AFS does not have that switch but rather a RF Gain pot there.
Terminal point 14 goes also to the intersection of R83 (to base of RF amp Q20) and R87 (to base of mixer Q22):
When following the schematics I am thinking of if measuring on the resistor R128 that goes to base of Q31 (or the base of Q31 directly) is a proper measuring point as well?
Ah, what the heck I measured at terminal post 14 and was able to adjust RV9 to 2VDC in USB mode with no signal input (RF Gain at max, i.e. lowest attenuation). Seems to be ok.
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