WARNING!!!
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Running the SSB calibration in automatic mode has the potential to burn out the finals.
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I've read at least 1 other thread where running the SSB calibration resulted in failures in the output stage.
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I now have a non-working QMX+ because of this.
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I replaced the blown final, but there is still another problem in the transmit circuit.? When I attempt to transmit from the diagnostics screen, I get 0 output power.? If I put a scope on the gates of Q503-Q506, I see what I assume to be a good signal, it's at least at the right frequency.? Q507 heats up when attempting to transmit.? I also note that the duty cycle for the 5V SMPS jumps up to around 75%, I assume because it's trying to push out so much current.
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I'm kind of stuck here, I have the tools (meter, scope, rework station), but I'm sorely lacking in troubleshooting skills for this type of problem.? This was my second QMX+ build, and I was ecstatic when it worked flawlessly on first power up.? I made some contacts on it, and decided to get it ready to try SSB.? Kicking myself for not reading more before diving in to the calibration or I might have not used the automatic option.
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I'm going to go read what I can find regarding an issue like this.? If anyone can offer any troubleshooting tips they would be greatly appreciated.? I'm looking for what to check, and what a reasonable result would be.? It's built for 12 volts.? Currently (pun unintended), the supply voltage drops to about 7 volts during transmit when I have the power supply current limit set to 700 mA.? I checked and the unit seems to be able to sink as much current as I dare feed it.?
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My first unit is on its way to Jeff.? I'm going to work through this one myself, I hope.
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Thanks and 73.
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Andy
WB9YXA?
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