RGB LCD shield (714) does not display any text, but backlight and buttons work

[pmw]

I just assembled the RGB 16x2 Character LCD shield. Running the Hello World program, I am able to change the background colors with the buttons. I can also see the "Took XX ms" printout on the serial console. But nothing ever appears on the LCD display. When I twist the yellow potentiometer counterclockwise, the top row turns dark. The bottom row remains as-is. But that doesn't get any text to appear.

Looking at the way I soldered it, I don't see any possibility of accidentally spanning multiple contacts.

Any ideas?

[adafruit]

hmm, it sounds like a minor problem...we can probably fix it! first up, try resoldering all the points (just in case)

if that doesn't work, please post up some clear photos of the front and back. if we see anything, thats easy to fix! if not, we'll get you another one

[pmw]

Hi. Thanks for the quick response. I used a multimeter to check for (a lack of) continuity between every two consecutive contacts. Everything appears fine. Here are some photos. Please let me know if I can try anything else to help diagnose the problem.

[adafruit_support_bill]

There are quite a few joints where the solder has not flowed well onto the solder pad (e.g. pin 1 of the LCD in the first photo). These may conduct OK when you press on them with a multimeter probe, but they are unlikely to be reliable connections. Also, there are some pins that appear to have no solder at all (third photo).

Use a clean, hot iron and go over any suspicious looking joints. They should resemble the diagram below:

[pmw]

Hello. I cleared up some questionable connections and took new photos. They replace the previous ones in the same location.

The only connections that don't have any solder are from the flip side of headers -- the side that goes into Arduino board pins.

[adafruit_support_bill]

On pin 1 on the LCD (rightmost pin in the first photo) the solder still has not wetted the pad. Pins 12 and 14 are suspect as well. Any joint where the solder has balled up around the pin is probably not making solid electrical contact with the pad. Any joint that has a rough or frosted appearance is likely a 'cold' joint and should be re-flowed until it is smooth and shiny.

[rynde]

Hi, I had the same problem, described above. Did all the re-soldering but nothing worked...

THEN I turned the the yellow potentiometer counterclockwise to about 10 o´clock... The "Hello, World" and time count appeared.

So my tip of the day is: Start with turing the yellow potentiometer and see if the problem lies there. If not go the re-soldering part. Less time consuming. Trust me, Hahaha

[andyx]

I am seeing the exact same thing on a shield I just put together.

I checked all my solders and then hooked it up to my scope and checked RS, EN, D7, D6, D5, and D4 on the RGB LCD (399) connecting to pins opposite of the soldered connections. Everything looks fine. RGB pins and potentiometer pin look fine.

I've grown spoiled on the quality of Adafruit shields and PCBs in general and I did not first manually wire the RGB LCD (399) to an Arduino to confirm the LCD was functional before I soldered it into the shield.

Andy

[andyx]

A great addition to this kit would be an 18 pin header which is soldered to the LCD shield.

This would allow a single shield to be swapped to any of the LCDs that the shield supports.

Andy

[adafruit_support_bill]

@AndyX - Check the contrast pot as rynde suggests. If you still don't see characters, post photos of the front & back of the boards.

[pmw]

I know it's been a long time since I checked in. I asked a coworker to resolder my board, since I am such a n00b. He did a very professional job. Now it works!