My banged up Yamaha DX7 needed a new display as it was a bit dim and I also wanted a backlight I did not want to pay €20+ for a new display kit. In this video I show how I did this.
Perhaps this would have been easier to just buy a kit but I did some searching and found out that it was possible to mount use any HT44780 (a display controller chip) compatible display and these cost around €4-6 on eBay. So I ordered the cheapest one I could find with a backlight.
While waiting for the display I discovered by accident that my display actually had a backlight, but it was very dim (the room has to be pitch black). Someone had at some point replaced the original display with one with an EL backlight which obviously had gone bad over the years.
The new display was obviously smaller than the one used previously. The mounting holes do not match the original ones.
When I looked in the service manual it seems as if the pin numbering was reversed. The display that had been mounted in my DX7 had the same pin numbering as my new one. So I am not sure if this is a mistake in the manual or if I am stupid
The new display has 16 pins instead of the original 14 pins. Pin 15 and 16 are used to power the backlight. This display had a built in current limiting resistor (R8 – 150ohm, see photo at the top).
If you are going to do this please check if your display has a resistor connected to the anode (pin 15), if not you must add one or you can destroy the display. I actually added one later on to reduce the intensity of the backlight as it was too bright when the room was dark.
I had to improvise a bit to make it fit in the metal bracket before mounting it as the screw holes will not fit. I used one of the screws, twisted a piece of single strand wire and used some nylon spacers so the display could rest on something
When the display has been installed you probably have to adjust the contrast to see anything. This can be done using VR1 on the main board