I have a QMX (80-20) for 12 V that I built last year. It worked fine on FD, and was used occasionally since. A few weeks ago I was running it into a dummy load. Controlled by fldigi. Power was a LiFePO? through a regulator at 12 V with a 1.5 A current limit.
?
After messing around with the fldigi settings until I got it to "transmit" into the dummy load. Output power and input current looked good.? Then I got distracted doing something else. After some time I looked at the regulator and it was showing 6.1 V at 1.5 A out. The radio is on, and the display works, but obviously something is seriously wrong.
?
WSJT-X communicates with it. I can change frequencies and modes.
?
I looked at the back of the main board with my IR camera.? The hot spots appear to be associated with Q507 and Q504.
?
So I've blown it up, but I don't know what I did. Is there a troubleshooting guide? I've opened it up and there's nothing visually apparent.
?
In talking this out I've sort of convinced myself that I have a shorted Q504, drawing too much current and heating up Q507. Does anyone have any better ideas? Is there any way to test this hypothesis other than cutting Q504 out of the circuit and seeing if the excess power draw goes away?
