Matti,
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? ?I was recently working on adjusting the toroid winding for power adjustment when my QMX+ display screen flickered quicky while handling it.? I look to see what may have caused it when I noticed my power connection was coming loose from the back of the unit.? ?After pushing the plug back into place, the QMX+ quickly powered off instantly.? ?
? After that the QMX would not power back on.? ?I tried everything under the sun to get the unit to boot back up.? ?NO GO.
?What I found was that my Zener diode D109 had shorted to ground.? ? I could test this theory by pressing the power on knob and holding my finger on either Q109 or Q111.? ?I am sorry but I forget which it was of the two transistors but anyway the transistor got instantly hot to the touch of my finger.? ?I then pulled one of the legs up on D109 to take the diode out of the circuit.? After doing so I attempted to power on the QMZX+ with 7v limited to 200ma.? ?What did you know, the QMX+ came back to life.? ??
? I repaired the unit by replacing the D109 Zener diode with a known good one.? ? (D109= Zener 3.6v 500mW)
? I think this may be the issue you may be chasing for why your unit is not responding to the power on button if I am following the event of how yours shut down.? ?
Also, I remember check that the resistance across VDD and Ground read something like 265 ohms.? ?It should be in the Kilo Ohms or higher.? ?You can begin there with checking with your ohm meter.? No power applied occurs.?
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P.S? ?
?I agree that for the no power out issue, double check that you added the jumper during your build.? ?Good Luck and hope this helps.
