Ty for your prompt reply!
floresta:
Even with a blank sketch I only see very feint "blocks" on the top row of the LCD.
A row of blocks on the top row of the display indicates that the controller on the LCD module is not being initialized properly.
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Sorry, I should clarify; when uploading an empty program (literally just the "BareMinimum" example sketch) then and only then I see the black squares. My main sketch shows text fine (LCDCrystal library is amazing!).floresta:
Another cause could be the relatively large current for the LED backlight causing the voltage to sag below 5v. You should check the Boarduino +5v pin both with and without the backlight connected.Checking the +5v is a good plan. I'll see if I can find a voltmeter. Do I check across +5v->ground?
I read somewhere that I need "at least 30-40 ohms" on my backlight. I think I have 165 atm. Is that likely to be insufficient?Edit: I get ~3.5v with and without the LED connected :S. Bad board?