16x2 RGB Positive -- not working

[ribo]

Just soldered up my positive 16x2 RGB, loaded libraries and tried the first example.
I'm seeing just a row of dark boxes in the display with no other functionality than adjusting the contrast on the blocks.

Is this a common problem to troubleshoot? Couldn't find anything on the forum about this.

[adafruit_support_bill]

Most likely some bad connections on the signal lines. Some of your solder joints look a bit starved for solder. The ideal profile is shown below. Touch up any that look suspicious:

[ribo]

I've carefully looked at each of the joints. There were some that looked like they had a decent contact however not 360 degrees of solder around the pin. I added more solder to any pin that looked solder starved and this didn't seem to change anything. I can't imagine these signals would be so sensitive to solder joint shape.

What can I probe (with multimeter) on my arduino R3 to make sure its output is correct before assuming the display is defective?

[adafruit_support_bill]

I can't imagine these signals would be so sensitive to solder joint shape

Solder can completely cover the joint and still not make electrical contact due to oxides or other impurities that prevent the molten solder from 'wetting' the surface. A good joint shape indicates good wetting. A shiny surface indicates proper solidification. Joints with a frosted appearance ('cold' or 'disturbed' joints) are full of stress fractures that are often enough to prevent conductivity.

Probing bad joints is inconclusive because the pressure of the probe often makes them conductive. That's why we judge joints by their appearance.

Are you running the Hello World sketch from the Adafruit-RGB-LCD-Shield library? Do the buttons make the backlight color change?

[ribo]

any sketch i run (currently hello world) just produces the black boxes with no backlight. There is no reaction from any button including reset -- always just first row of dark boxes. The potentiometer just adjusts the contrast of the dark boxes.

[adafruit_support_bill]

any sketch i run (currently hello world)

Hello World is currently the only example sketch for the shield. Are you sure you are using the right library?
There are several other LCD libraries with Hello World examples. You need to use this one:
https://github.com/adafruit/Adafruit-RGB-LCD-Shield-Library/downloads

[ribo]

Bingo -- you got it. In my haste I wrongly assumed the LiquidCrystal examples were for this shield.
Working now, thanks for your help.