Re: 30m QCX working – but not for long....

Alan G4ZFQ

- Glen - the decoder does decode on the LCD when transmitting.
I do not know the significance of that, maybe Glen can expand his comments?


First a reply to your following post, I think the state of the clock outputs is correct, I do not see how they would affect your stated symptoms anyway.
- Alan - actual voltages IC10 pins 1/2/3 10.8v, pin 4 0v, pin 5 9.6v, pin 6 9.7v, pin 7 11.0v, pin 8 11.6v;
Are you looking at the manual? These voltages do not match. IC10 pin 5 should be fixed by a potential divider, something around 6V if measured with a DVM, Hans measured 4.2 with the inbuilt meter.
Check R39, 40 and joints around here.

More interesting perhaps, Q7 D 0.4v, G 0v, S 0v.
Shows it is not actually turned on. I'd expect the drain to be 0V. Have you checked the resistance to ground here? And you are positive C21, 22 are the right way round?

Could Q7 fail gradually?  I had assumed, maybe wrongly, that it either works or it doesn't.
Usually that is correct, but we are looking for a fault, just as likely to be a bad joint as actual component failure. The intermittency could be a bad joint but intermittent components are not unknown.

73 Alan G4ZFQ

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