开云体育

I have a QMX mid-band build - the LCD works, displays characters properly, but the LCD backlight won't turn on. The radio otherwise works well.

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LCD doesn't turn on after firmware factory reset - I also confirmed in settings that the backlight is ON.

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To try to isolate the issue, I subbed in the LCD from my low-band QMX and the backlight works properly with the mid-band main PCB, so the mid-band main PCB and connectors doesn't appear to be the culprit (nor is there a settings issue).

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I reflowed the pins on the mid-band LCD PCB, as well as the solder connections between the LCD itself and the PCB - I also checked continuity on both solder joints for pins 15 and 16. In the process I was pleased to observe the backlight functioning when I check continuity between 15 AND 16, on both sides, so the LCD backlight is functional in that context at least.

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Anyone have suggestions on next troubleshooting steps?? Thank you so much for the help, I'll report back on progress.

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73 KD2WQI

If shorting pins 15 and 16 turns on the backlight, then check Q301.? Either it has a problem, or its connection to the pin on JP303 is not good, so the signal from the processor can't turn it on.

Stan KC7XE

Stan Q301 was indeed the culprit! I have a replacement coming that should resolve the issue. Appreciate the excellent suggestion and thanks all for making this list so useful.