Re: [QCX] Q6 appears shorted/ blown (Pulled Q2, now Q1 gets hot immediately)

Jess Gypin <ontarget1911@...>

Ok, so here is the current scoop.
Found a small cold solder joint in the supply voltage chain. Not like me, used to be NASA certified back in the day. Probably in too big a hurry.
Long story short, got the radio running and aligned. Sort of. Not getting a lot of movement in the balance and hi and lo phase adjustment. Peaking cap high at mid point like it should be. No transmitting, waiting on replacements. 
Some issues. If I turn up the audio gain much passed 1/4 way, I get feedback howl. When turning the encoder, I get scratching on each turn. When pushing the encoder down I get scratching in the audio. Seems to have a little random hum, ac style, in the audio chain. Depends on what the board is sitting on and would probably get a lot better in an enclosure. Anyway, receiver works well, tunes well. All working, just no transmit for now. Just waiting on parts. Thanks for the help and tips. It really helped to this point.


Sent from my iPhone

On Dec 20, 2017, at 3:41 PM, Bob Sutton via Groups.Io <zl1rs@...> wrote:

The display back light is powered from the 12V line, but the electronics that drive the display (IC2) and the contrast pot are both powered from the 5V line.  As Al says, check the 5V line (the output of the 7805 regulator IC11) first.

On 21/12/2017 10:25 AM, Jess Gypin wrote:
So I took a chance and powered up the board with Q6, Q1 and Q2 pulled. Q6 measured shorted out of circuit checking the front to back with an ohm meter. Display light up and that is all. Adjusted the display trimmer cap and no change in the brightness or contrast and still nothing displayed. 

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