Edit : I had originally posted info about the 2004, then I saw you said pro94 , but the squelch control may just a 10k potentiometer. I could not find the parts list for your radio but it's likely similar.
The wiper inside the housing may have some corrosion that is a common problem. Also it's possible it's snapped off and there is no contact with the resistor of course. Try exercising it by rotating it like a hundred times and this should clean the track . You can do this with the radio on and if nothing suddenly happens, then put an ohm meter ( multimeter) across the pt terminals with the radio off and as you rotate it check for changes in resistance. Should be maybe 5 or 10 ohms to 10000 range. You could bridge the terms with a 2 or 3 k ohm resistor and see if that shuts it up.
If that works and you still can't get the control working try Deoxit or gasp_ WD40.
If you cannot get results with these simple things, it's a different world beyond that. Printed circuit radios are nerve wracking , you may want to consider recycling.
Could be a cap , like Redhat suggested. Not often this is a problem with caps in radios under 50years old, although I have heard of cheap ones already blowing out in flat screens so you never know.
Caps can be tricky to test in circuit. A bad one will be open or shorted, but it usually open , although Caveat: they may read ok on a mulitmeter in situ. I didn't look at the schematic but most likely in the immediate area of the pt if the radio works correctly otherwise , don't venture outside of the immediate components serving that circuit. If you do remove anything, use a low wattage pencil and you really need some specialized tools .
Good luck '
Topic: Pro-94 squelch problem (Read 3088 times)
