Re: QCX-Mini Display Issue

Ronald Taylor

Hi Ernie, since I wrote that procedure, I take full responsibility for an obvious mistake in it and will send a correction to Hans tonight. That was supposed to say pins 7 and 20 (not 21). There will not be any voltage on pin 21. Please look for 5 volts on pin 20. It probably is there since you saw it on both sides of both inductors, but make sure. After that one of the suggestions is to look for soldering issues between IC2 and the display board. Since the display is on a separate board on the mini, pay close attention to the soldering of the pins on the interconnects between the two boards. Ground pins especially need extra heat to get good connections. You can also use an ohm meter to verify connections from the Display to IC2. The schematic will show which leads connect to where between these two devices. It's a little cumbersome with the Mini but you can do it if you turn the unit up on its side and measure from top of the display board to bottom of the main board on IC2 pins. If a particular connection isn't there that's supposed to be, check soldering and also try to isolate if it's on the main board or the display board. On very rare occasions I have found an open circuit trace that isn't even visible with the eye. It can usually be easily repaired with a jumper wire if that's the case. Hope that helps ... Ron

On Thu, Mar 24, 2022 at 5:24 PM Ernie Bailey - N2DGQ <ebrcdddcdc@...> wrote:
I have just completed my second QCX-Mini this one for 20M.  Upon power up the display was one (1) row of blocks.  In looking at the troubleshooting procedures by Ron WA7GIL, item #2 
IC2 may not be getting power. Check for 5 volts on pins 7 and 21 of IC2. If either is missing check for open condition in L6 and L5 respectively. This is easily done by checking for 5 volts on both sides of each inductor.
I found pin #7 has +5VDC, but pin #21 is not getting +5 VDC.  CheckingL6 & L5 they both have +5VDC on each side.  C35 which is tied to pin 21 does not have +5vDC either. 

I have checked and resoldered all pins for IC2 as well as the header connector pins connecting both boards.  IC2 is seated properly.  I am stumped.  Could IC2 be defective? 
Any further troubleshooting ideas would be helpful.    

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