[Don_G]

Ray, thanks very much for your continued help. I have good news. I borrowed a more modern digital meter and the resistance measurements look good – VIN-GND is 8.7 kOhms and VCC-GND is 16.7 kOhms. Voltage is still correct. My old analog meter must have a problem with resistance.

I reinstalled the ICs and the LCD and powered it on with the USB. The LCD lit up and displayed appropriate information! I then tried it with the transformer and this time everything worked as expected. I can’t explain why it didn’t work previously since I didn’t make any changes to the board. But at this point I’ll move forward with additional testing.

I have one question for you. When powered with USB, the on/off switch has no impact; the unit is always on. Is this normal behavior?

Thanks again for your help.

[Don_G]

Hi, Ray. Thanks very much for your guidance. With your course in meter reading, we were able to determine that the voltage looks good. With the USB as a power source, VIN-GND is close to 5V and VCC-GND is close to 3.3V.

However, it appears that the resistance is way too low. For both VIN-GND and VCC-GND, the resistance is under 1K ohms. I’ve studied the back of the board closely with an eye loop and I can’t find a solder bridge. The only thing I can see is some filaments from solder wick (I believe). I’ve attached a couple of pictures – one each of the front and back of the board. Perhaps you can zoom in and see something I can’t.

Thanks again for your help! We’re building this as a family project so it’s a good learning experience.

[attachment=1:2yepb0oq]IMG_0708.jpg[/attachment:2yepb0oq]
[attachment=0:2yepb0oq]IMG_0717.jpg[/attachment:2yepb0oq]

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