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.