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Re: QMX Failure #qmx


 

Nico,
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Check IC503 (four 2 input AND gates). Two of the 4 outputs were shorted on mine.
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My QMX+ was working flawlessly for a long time.? When I added the SSB FW I was playing with the VOX and
it might have had too much gain? along with a possible intermittent coax cable to my QRP dummy load.
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Anyway smoke started pouring out of the case and one BS170 was cooked. After replacing the BS170's (decided to solder the ground leads just to the top pads on the board) is
when I had it in Message Repeat Mode and all of a sudden the receive got much louder.....indicating a open coax or bad connection. I purchased a new PL259 to BNC cable without
the lousy adapter.? Waiting for new transistors (and IC503) from Digi-Key. Transistors this time were still good - but I didn't realize this until I removed two and removed the IC.
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Still trying to figure out why the outputs of the gates to the inputs (gate) of the BS170 went???
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Michael

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