Help with strange audio fault #qcx


Ted 2E0THH
 

Just before I remove the QCX40 from its enclosure to fault find, I thought I would share it in case anyone else had ever experienced a similar issue.



My QCX40 rev4 has been performing beautifully for about a month now since it was built.
It is installed in a bespoke enclosure with a alternative volume control with a power switch.

The fault first manifested itself about 2 weeks ago, I had left the set on all day but when I went to listen out later in the evening, there was no audible output.
I had some work to complete so I turned it off for a few hours but when I switched it back on, all perfect again!
It remained fine for about 5 minutes and then it just went quiet again, not instantly but as though a volume control was being turned down.
It was now late so I left it overnight with a view to fault find it in the morning.
Of course in the morning all fine again!

It has been fine until a few days ago when the fault returned.
If I turn it off for an hour, it fires up again fine but then the gremlin in there turns the audio down after about 20 secs. This is fairly repeatable. If I fire it again instantly, the fault hasn't cleared.

A very quick check at low power during fault conditions demonstrates it is still able to transmit on the selected frequency.
I am suspecting a capacitor issue in the audio circuitry or earlier in the signal path.

I just wondered if anyone has experienced anything like the same issue?

Many thanks in advance.

73s Ted M7ECH

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