[TenTec] Argonaut V squelch problem!

[Ken]

Hello all,
First time posting to this group.
The used Argonaut V I bought a few months ago has a squelch problem.
The green light is on all the time. Rotating the knob fully CW or CCW has no effect.
The schematics on-line are really poor. I can't tell anything from them.
I have no idea what voltages to look for or on what pins. On the board says it's R-92.
The Volume/Squelch control seems to be practically "hermetically" sealed as far as getting any cleaning fluid into it.
It rotates very smooth. I don't believe it's dirty.

Converting it to an RF gain control would probably be the sensible thing. I may sell it in the future so I would like to keep it original.

Any help getting it working again would be very much appreciated!!
Thanks, Ken, W2GIW