Locate R-148, a 47 K ohm resistor between pins 12 and 13. Cut a lead of this resistor, But be sure to leave enough lead on both sides of the cut to solder to. Patch in a 100K ohm resistor. Make sure there are no solder balls or short circuits. Now your squelch will operate more smoothly.
Addresses appear below.
Please ignore any mis-spellings, mis grammer, etc. Old soldiers never die. Young ones do.