I own since few months a ROLAND MC 505 Groovestation. I love this synth (YES ! it is a true synth not dedicated to DJs !!!) because there are a lot of knobs and buttons you can interact with.
Since I own this device, the LCD has some missing lines and dots, and that is because the original LCD screen from Roland is a very poor quality one. So, after reading many posts about how to DIY, i did it, and that was not so much a pain...
You have to buy a LCD Display Character Module 2 lines / 16 characters, compatible with the HD44780 protocol. You can find this kind of parts on Aliexpress for few euros, or around 10 euros with Europeans electronics resellers.
602-16x2-HD44780-Character-LCD-Display-Module
Then you have to remove the existing one. Start by unmounting the back cover :
You can see the LCD white flat cable, on the right of the two blacks.
Carefully unplug all flat cables using a small screw driver. Go slowly as sometimes it is not so easy. Do not force anything.
Then remove the motherboard. You must loosen all plastic bolts at the back of the MC 505 plus some screws. Again, stay cool !! Plastic bolts are fragile.
So you should be here. No you can push carefully on the window covering the LCD screen from the inside with a small plastic tool, then finish the job from the outside with the same plastic tool. The LCD window is stuck with adhesive double sided tape. I prefer this aproach rather than trying to take off the window only from the outside at the risk of damaging the case. More work, but less risks.
Then you have access to the LCD screws, and you can remove it.
As there is not enough room to place the generic LCD board, you will have to cut some small pieces of metal. Use a metal saw blade. not cutting pliers !! And again, go slowly....
The schematic below shows the connection mapping between the generic LCD and the MC 505.
With a good solder iron, desolder the flat cable from the original LCD screen and resolder, wire by wire to a flat cable, like those used for IDE hard disk.
Before remounting you new LCD screen, make some tests with the contrast (screen tested and connected to the MC). It is possible you will have to change the 10K resistor value to another, depending on your screen ratio.
The final result with a blue LCD :
..
