I'm pretty sure that datasheet you referenced is not for the glcd you have.
I looked around and there appears to be several DG-12864-xxx models
that are all slightly different. The differences seem to be in the color of the lcd and backlight
with the main power, data, and control lines all being in the same positions.
That datasheet you referenced is for a EL backlight. EL (ElectroLuminescent) backlights use a high frequency high AC voltage.
The one in this datasheet uses up to 150 VAC at 1Khz with a typical setting of 100 VAC and 400hz.
Since the backlight previously was working. The panel you have isn't using an EL backlight.
There would be no way to get an EL backlight to light up with just DC voltage.Do you know how you wired it up when the backlight was turning on?
- This would really help even if it was when
the power supply was shutting down and the backlight was going back off.Was the backlight connected up without a resistor? (A to +v and K to gnd)
When you say:
GLCD pin 19(LED A) goes to a 330ohm resistor then to +5V(Arduino).
I assume you mean you mean pin 19 is not connected directly to 5v but that power goes
through a resistor like this - (I couldn't see this part form your earlier photos)
glcd pin 19 ---------- ( 300 ohm resistor ) ---------------- +5v
For the backlight, It comes down to about 1 of 3 things at this point:
1) incorrect wiring, broken wires, wires not making connection.
2) the backlight is burned out
3) the resistor is too large and there isn't enough current to light the backlight.
You could try hooking up two 330 ohm resistors in parallel - both connected to pin 19 and both connected to +5v.
That will reduce the resistance to 165 ohms.
Turn off all the lights and see if you see any kind of glow at all.
There are some ways to diagnose this but it depends on what you have available.Do you have a voltmeter?
What other resistors or potentiometers do you have?
The contrast pot not working concerns me.
When rotated to one side, all the pixels should be off.
When rotated to the other side all the pixels should be on - regardless of what the sketch is doing.Do you have an ohm meter?I'm still curious where did you get/buy this glcd?
link to purchase site?