Re: Low audio gain and no power out with 20m QCX
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Hi Daniel
One of Clk0 + Clk1 is shut down. The other one is set to 27MHz (straight feed-through of the reference oscillator). I forget off the top of my head, which way around it is. This was not in the first firmware version but was released soon after. It resolved the issue of the side tone volume being a bit inconsistent, and it also greatly reduced the clicks on the Receive/Transmit changeover.?
73 Hans G0UPL
On Tue, Dec 5, 2017 at 4:52 PM, Daniel Ekman SA2KNG <knegge@...> wrote: If the original problem was a short on one of the Q1-Q3 then Q6 will probably be dead as well. Change it to the new MPS751 (or similar) instead of MPS2907.
I don't see any reason that Q5 should be damaged from this scenario though. Also, the sidetone comes in much later in the signal path. Maybe Hans can confirm if the Clk0+Clk1 is shut down during transmit so no receive mixing is on during TX thereby deactivating the stuff before R27 pot. Or measure the Clk0+1 pins to see if this is the case. Scope Clk2 all the way through IC3 and to the gates of Q1-3 to see if they get a signal through, depending on the fault that IC could get +12V on the pin3 output and fail. DMM to check that the RX/TX switching is working at IC3 pin 12 & 11.
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