Re: Help with strange audio fault #qcx


James Daldry W4JED
 

Hi, Ted

Get a can of computer keyboard duster, turn it upside down so it throws liquid, and spray the board with it until you find the spot that brings the audio back. Circuit cooler and "canned air" are the same thing, except that circuit cooler cans have a dip tube so they always shoot liquid out. Canned air has no dip tube, so it always shoots gas, unless you turn the can upside down.

Spot cooling works really well for localizing thermal drift. The main problem with it is if you cool the spot enough to get condensation the water can mask the change.

Jim Daldry W4JED

On 1/10/19 9:31 AM, Alan G4ZFQ wrote:
I am suspecting a capacitor issue in the audio circuitry or earlier in the signal path.
Ted,

I'd suspect a dry joint somewhere. Maybe a capacitor charging up when it should not? Component faults are rare, construction faults not so.
But whatever, start with checking voltages against Hans' chart. Use the built-in meter. It might take a while as the fault is intermittent, maybe a good look at joints?

73 Alan G4ZFQ

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