Re: #20m JP 3, 4, and 5 #20m
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The schematic on pages 149-150 of the manual shows signals on front panel JP1,2,3. Not sure what you mean by "the display is truly black." Does the backlight light up? If not, you have an open path to the LEDs in the LCD. Have you tried adjusting the contrast pot? You can test voltages at the top of the front panel pc board which go to pins 1-16 of the LCD. The LED ungrounded pin should have voltage on it and the contrast pot should move that voltage when you adjust it. Most likely you have a bad solder joint on the front panel PCB or on one of the pins on front panel PCB JP1,2,3 or mating connectors on the main board especially on the ground pins. It's difficult to probe these when the QCX+ is assembled but it's relatively easy to probe LCD signals at the top of the front panel PCB and trace them to their final source or destination at the processor. Probe very carefully to not short adjacent pins on the processor.
------ Original Message ------
From: "Syd via groups.io" <nhuq1@...>
Sent: 9/17/2020 9:30:03 PM
Subject: [QRPLabs] #20m JP 3, 4, and 5
Just starting to test/align this rig. The display is all blacked out! Trying to see what is supplying the voltages and signals into the display module, I see that JP3, JP4, and JP5 are the connections to the display board and it sure would be nice to know what these three JP pins are connected to, especially the VDC and gnds! I cannot find any place in the QCX+ manual that shows what is on these pins. Is there a list of what is on these pins?