Calling all ELMERS HELP me please

[Crambone]

I have a ARF2001 Scanning Transceiver that is giving me issues.
I checked voltage as listed on 3.6.2 in the service manual and all Line No. (test points) Pin 10's on all boards and all are without the 13.5Vdc in AM Position, when in LSB or USB I do get the 13.5Vdc on all Pin 10's.
I checked the 3 position USB / AM / LSB switch and it is switching the proper 13.5Vdc
All other Line No's (test points) show correct voltage per 3.6.2.
I replaced all Electrolytic Caps and no change.
All function switches on the radio are performing properly.
Also I noticed on USB I see a nice flat line on the scope and show modulation but only swing to 1 watt, on AM I show a normal pattern on the scope with zero modulation and dead key of 7 watts, on LSB I'm showing an AM pattern not a flat line with modulation and 1 watt. I get this on both Antenna A & B.
All frequencies on all 40 channels TX are on the money.
RX frequency is off on AM by about 2MHz (example ch20 rec on ch22), LSB & USB RX is spot on frequency.

I have the owners, service manual and schematics but they are too big to post on here. I can send via email if requested.

[LateLesley]

My radio knowledge in very limited. Only popped in here to post a link to where folk can see schematics for this radio. They can be found here - http://www.cbtricks.com/radios/arf/2001/index.htm.

There's 6 links at the bottom of the page.

What a nice old school radio. Best of luck in repair of that beast.

[Crambone]

I also have the service manual. I can email to anyone if they require it

[Crambone]

So being I’m new to all this schematic and troubleshooting I believe I’ve narrowed down my issue to the audio board A3 and possibly the Op Amp or IC.

[LateLesley]

Hmmm, that's funny, because looking at the schematic, I was thinking you should check 3U1 (MC1458P op amp) and the two transistors 3Q7 (2N3096) and 3Q6 ( TIP 32A). My reasoning was it was part of the circuit switched in, with switch S5A, which I believe switches between upper, lower and AM?? Though What put me off mentioning, is the differences in testing between the USB and LSB. That makes me think that maybe the LSB circuit might have problems, and could be affecting the AM side of things.

[Crambone]

It looks that the AM and LSB share a signal that USB doesn’t so you may be onto something. I haven’t had a chance to get back at it yet.