HP8920A problem locking up

[bradlington]

HP8920A

I have the following problem with the HP8920A.

Over a short period the machine did the following:

Lost seconf audio generator(normally used to generate CTCSS etc)
Lost the audio on speaker of unit.
Unit would work for short while and lock up ---no chaning on menu .
Continuos ERROR 0040 after boot-up.

I did the following :

Removed each all cards in unit and cleaned with brush and compressed air.
Removed and reseated ALL Eproms.

Now the unit powers up and displays"ALL TESTS PASSED"--but still have the following issue:
All works but ;
second generator still faulty
no audio
deviation seems to be limited to max reading of 1,8 Khz


This is the strange thing : When I adjust the squelch from fully counter clockwise to clockwise-as soon as the squelch is triggered- the screen locks up and only way to resore is to power rest unit .

Any similar issues.

Thanks

Bradley