Panasonic (National, Levear) VP-8132A, no right-channel modulation

[Hifi Necromancer]

Hello from the Pacific Northwest USA.

I'm hoping I can get some assistance with my Panasonic VP-8132A AM/FM/Stereo signal generator.  The issue is I get no right channel signal through either the composite output or the RF out.  In every modulation mode the left signal is just mirrored to both sides when decoded.  I've verified that when viewing the composite waveform directly there's no right channel information in any mode.  There's no service manual available and this is a little outside my field of expertise, so any help is appreciated.

The areas of interest are the "stereo" board and the "AF source" board below it, both accessed from the top of the unit.  On inspection I didn't see any obvious faults.  I probed the connectors linking the two boards looking for any sign of the R signal and found none.  I found a left and an inverted left signal on stereo J1/source J6 and that's it (besides some logic and power supply).  It seems like there's no R signal getting to the stereo board.

I removed the stereo board and probed the connectors again on the source board in case something was grounding the R signal, but got the same as before.  On the source board, the R signal is definitely being generated, as it's present at TP4 and I can toggle the frequency between 1k and 400hz from the front panel control.  I can follow the signal to an AD7523JN but I don't see any output at Iout1 or Iout2, and I'm not sure if there should be. 

Does anyone here have a working model that I can compare readings with?

[Hifi Necromancer]

I took a picture of the bottom of the board and overlayed it with the top so I could trace the signal a little more easily.  The right channel signal takes only one path and lands on the D2 pin of an ADG433 CMOS switch, U20 on the source board.  D2 and S2 form a normally open "contact" and are controlled by a bit input at In2, which if fed by one of the UPD65012 PGAs on the same board. 

The In2 bit never goes high, no matter what.  It should at least be enabled when modulation mode is set to R, but I can "spam" the front buttons and get nothing.  I checked and it's not shorted to ground, and it ties directly to the PGA, so I think that bit output is simply not working. 

I can't find any data on the 65012 unfortunately...