Thanks!Robber1956 wrote:Well done! Congratslogix wrote:(preliminary) SUCCESS!!
Now if you connect the new display with all lines visible exatctly the same you're there.
Yes, I'm just going to finalize the testing of the contrast etc. and I'm ready to put in the new, undamaged display. But get this: I managed to "fix" the damaged display!
I had nothing to lose, so I removed the metal frame again, dipped a Q-tip in some isopropyl alcohol and cleaned both the PCB contact surfaces and the side of the rubber contact strips for the LCD (I didn't pull up the end that attaches to the actual LCD glass display though -it's still sticking to that surface for some reason). But.... I have to take care not to not touch anything or possibly even sneeze , because then some character pixels will be gone, so apparently the bending of the metal frame lugs for the display has to be just at the right angle and pressure. No doubt it's done by machines at the factory making them. Nevertheless it proves that my connection is correct, which is good enough for me.
Another interesting observation: it seems that the backlight only consists of a single LED at the side/end, and together with a diffuser (a semi-transparent plastic sheet with some sticky glue or tape on each end) it makes the light spread evenly behind the display!
I don't really understand how the LED backlight connection is set up as I was expecting separate wires/pins for this (as with the original Roland display), but as you know it lit up when connecting just the +5V and GND pins for the 14 pin connector. I assume this means the display has already been configured for +5V. Does this seem right?The inquiry of putting a trimpot or resistor to adjust the brightnes of the backlight and the contrast (two different things) also looks very promising. I shouldn't put 5.0v directly on the led, you always need a resistor to prevent the led from getting overloaded and it also will be far too bright.
There was some mention of pins 15 (LED anode) and 16 (LED cathode) in the 1602xxx-2.1 datasheet, but it wasn't especially clear, so I don't know what that means.
I've just tested the contrast setting by putting a small trimpot with the two side-pins connected to pin 1 (+5V) and pin 2 (GND) while the middle pin going to pin 3 (V0). I'm not sure of the resistance (couldn't find any marking) but I think around 5K Ohms. I tried adjusting it from one side to another, but didn't notice any contrast difference
I then adjusted it to measure +4V (as suggested by Rasputin) between pin 1 (+5V) and pin 3 (V0), powered off and de-soldered the wires from the display and measured approx 2.5K Ohms between the wires that went to those pins (and approx 2.9K Ohms between the wires that went to pins 2 and 3. That would likely make it a 5.6K trimpot I guess. Strange that it made no difference though.
It can't be that pins 4 and 3 have to be exchanged? Probably not as it's not likely to display things/display correctly without the pin 4 (RS/Register Select) connected to the right place. Maybe it'll work better on the new/undamaged display.
Any ideas? If you have the opportunity to check if your display's "V0" pin goes to pin 4 on the D-110 CN1 connector it would be helpful.