Another D109 failure here. I think. :-(
I have a QMX+ Rev2 that has been working for over a month. (SMPSs integrated into main circuit board)
Today I turned on CW practice mode for the first time...
As soon as I plugged in my iambic key (It works fine in a different QMX+) it shut down.
I tried powering up again and for a few iterations it would come on and then power off right away.
Then no response at all. Dead.
I suspect that this is just a coincidence and not the actual cause.
IC 101 and D103 were hot and D109 was scorching when I held PWR_ON. So I stopped active troubleshooting for fear of further damage.
I lifted D109 and the drain on Q111 and sure enough it comes to life with the 3v from the 3.3v linear supply.?
With Q111 still lifted, but D109 re-connected, it again, will not power up.
Re-lifted D109..
Actual measured voltages in 3.3v SMPS "bypass" mode:
VDD = 2.97v (from linear reg.)
VCC = 4.98v
ADC = 3.3v
+12V = 11.9
Seems reasonable considering, but the Diagnostic screen shows 12v+ = 13v, VDD = 6.6, and VCC = 5.6.
Can someone explain how those values are measured and/or calculated?
Source on Q111 = 10.6vdc. With a scope I see a PWM'd square-ish wave from +11.9 to +10. Not returning to 0. My suspicion is that this is due the Q111 drain floating.?
Thanks for your insights.
--
Randy, N4OPI
