Re: No output QCX 40 output drains show 1.6 watts in receive

George Korper

Thank you Alan,
Ok so far. First I have a QRL dummy load and it is plugged in. 
I went ahead and replaced Q6. No change. 
I will try to get voltages on IC3, but I didn't see the voltages listed in the list, are they somewhere else?
May I remove the LCD do get to to IC3 and still take the voltages?
The QCX was running fine, but my straight key which was plugged my have
come on while the OLG was connected and running WSPR. I looked at the key and a tiny, tiny speck
of some material was caught in the minute  gap and it took a piece of paper to remove it. If it can happen it will happen I guess.
That is one supposition. In my collection of cables I pulled the key when I realized what was happening and the plug hit something
on the open end of the QCX and some sparks flew. After I cleaned it up, thinking all was lost I checked the QCX and I did see output,
when I realized I had high SWR for some reason, and it turned out what ever happened back in the rat's nest the MFJ SDR switch
was no longer working. The QCX seemed fine, at least in my nervous condition but now I was rattled and decided I should to wait until
morning. I was wrong, now there was no output. The bottom line is at sometime the QCX was operating with the WSPR running and the key shorted, As for the MFG which has an RF sensor that may have just been bad for a while and causing the high SWR. I  noticed that the high SWR caused the QCX to go up very high in power. So as for the cause it is murky!
I have read Han's manual over and over and I do wish I had just settled for seeing that it is better off running at 2 to 3 watts out on my wattmeter
which is 5 watts into a dummy load using the internal rf probe. I would have saved the groups time and a lot of anguish adjusting toroids, etc.

I'd change Q4 but first I will await your reply on IC3 and the removal of the LCD.


On Tue, Dec 10, 2019 at 10:56 AM Alan G4ZFQ <alan4alan@...> wrote:
>   I replaced the three BS 170's  in the amp and using
> internal wattmeter show no output


>and 1.6 watts on the drains during
> receive..

The wattmeter only gives sensible results on the output when going into
a dummy load. All other checks should be with the voltmeter.

> I replaced Q5 and no difference.

Check Q6 voltages.  Your "1.6 watts" seems to show that is faulty.
Also check IC3 voltages.
  >Not sure which voltages to check.
As in the manual.

Do you know what happened to cause this? Any observations?

73 Alan G4ZFQ
> I realize there should be no watts on the drain in receive as I checked
> my QCX 20.
> Thanks,

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