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I'm hoping I can get some guidance here. I've used my 20m 50w QRP Labs PA for several years with a QCX mini. No problems. However with the QMX it appears the PTT output is not triggering the PA. No red light comes on and the PA doesn't produce additional power. I've checked the continuity of the socket to the circuit board, so no problem there.?The diagnostics screen shows the PTT enabled when I press T.?

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Voltages at the collar and tip of X201 are both at 0V on receive and on transmit, so something is amiss with the circuitry around Q203 and Q204 I think but don't really understand the schematic. I'm lost on what to do next. Suggestions??

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Many thanks in advance.

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73, Mitch NK3H

Hi Mitch, PTT output needs to enabled on a per band basis in the terminal application. It’s disabled by default. You can refer to section 8.5 of the operation manual (TX PTT +5V). Although unlikely, but if you modified your 50W amp to take active-low for PTT, then you need to take a look at as well.

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73 Zhenxing N6HAN

Thank you Zhenxing. Definitely a RTFM moment. All good now. 73, Mitch NK3H