Contamination on chineses 5110 lcd display

I bought 2 of these to test them and it appears to be contamination on the figures that i enter. In this case the test for adafruit display. I downloaded others but this is the only with a recognizable contrast which is set to 1, i know is recommended higher but im indoors and higher that 3 it only shows black boxes.
I'm using the pcd test example.

No picture found!

Oh, here it is!

Possibly contrast adjustment, or too low a voltage somewhere.

It was indeed voltage, read that this could work either 3.3V or 5V and decided on 3.3V as some sites said it worked better. Now with 5V is clean and the contrast is in 60.

Thank you!

Dieghog:
It was indeed voltage, read that this could work either 3.3V or 5V and decided on 3.3V as some sites said it worked better. Now with 5V is clean and the contrast is in 60.

As a general point, LCD displays are definitely voltage-critical, so a given device will be designed for one voltage or the other unless it has some option jumpers.