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Qcx 20m problems #bpf #alignment

morseoneuk
 

Hi, I managed to assemble my QCX 20m  a few weekends ago. It all went together well following the build instructions.
The alignment however was another story, all booted up fine on power on. relevant menus selected and
menu 8.7 peak bpf could only manage 7 on the scale. C1 only partially closed.
8.8 IQ balance   about 4
8.9 Phase lo      about 4
phase hi     about 4
Hooked up a dummy load and on key down   nothing showed on my power meter although I could hear my transmission on another receiver.
When I switched in my antenna I was able to hear a few signals  but they were quite weak,  ( s 7 to s9 on my other transceiver)
So I rechecked all soldering, no obvious cold joints or overlaps.. my torroid windings removed and resoldered,, rewound T1  and re tinned all wire ends before reinstalling.. Resulting in no difference.
Then disaster, I sat the qcx on the bench while still powered  on, on top of a small metallic screwdriver,
 there was a resulting short fizzle ( no smoke escaped ),  the lcd screen went blank. and  the 5volt regulator started to run extremely hot.
On checking regulator was struggling to maintain about 2 volts and was too hot to touch after about 10 seconds. Traced the short to ground in IC 3. 74act00
 which I have replaced, display now boots up again, all menus function , but on alignment C1 is having no effect when trying to peak BPF. it continually displays  0.
The regulator now remains warm but not too warm to touch.
My fault finding knowledge is limited , I guess I'm hoping someone may have had a similar problem, and be able to point me in the right direction.    What else have I taken out?
 In the meantime my QCX20 has been consigned to the " try to repair later drawer "
Best regards  Scotty Gi0bey..