Hello Vogons,
I became interested it MT32 display replacements a while back but have only found a few mentions here and there about any current projects. I have ran across this sed1200emu project a few times but there is very little information and documentation about it.
http://sensi.org/~tnt23/sed1200emu/index.html
So to satisfy my own curiosity I decided to take some initiative and try and build one of these, and maybe get the ball rolling on some options and collaboration for something like this. My displays work fine on both of my MT32's, but I wouldn't mind preparing for a replacement or finding something that looks cleaner and brighter than what is stock.

I have PCB's built, IC's programmed, most things plugged in, but I am stuck and do not wish to continue without more information and planning for what to do next.

Everything powers on with the new display with a seemingly initialized row, but data does not seem to be registering from the MT32. I have two ideas that could be causing this.

First, I am not certain if the oscillator I chose is functioning properly. When measuring with the oscilloscope it seems to be all over the place and not produce a solid sine wave. I think this will be the first thing to troubleshoot because I am certain this needs to be working correctly. I am not very familiar with oscillators so it has been difficult for me to know exactly what is required.

Second possible issue is that there are about 6 single pins available on the backpack PCB that are labeled SCK0, SCK, MISO, MISO0, MOSIO, MOSI that I am not sure are required or not for function. The project page does not mention anything about these, or where they might patch to the MT32 if required. I have been scanning through the MT32 service manual trying to see if there is a clear easy spot, but I am not willing to poke around and test without knowing for certain. The project page does mention that there are ground pins that need to be connected for continuity, and those were absolutely required to get the display to power on, but the other pins aren't mentioned.

edit: Also, there is a reset pin on the backpack that may need to be connected but there is no mention on the project page. Reset is high on the atmega, so it may need to be pulled low or connected to MT32 reset line. But so far grounding this to low doesn't have any affect.

Schematics and PCB are available on the project page if anyone cares to take a look, and I can also share some of the files and mouser links to parts that I used if anyone is interested in helping along. I have also sent an email to the project developer and waiting to hear back about any further information.