I think that with a little bit of effort, you could build the world's most ghetto MT-32. 😁

Just find a photo of the real new MT-32 as a guide, source the missing parts, apply a touch of heat and solder, and off you go.

That would be glorious.

so where does this go into? is it a pcb from a keyboard synth or something?

It was a set of two board. The second board is a E-20 control logic (keyboard controller, sequencer, arranger). The man who sold me it found these boards in a scrap and does not have any other parts or cables

I will try to identify power, MIDI IN and analog output and run MT-32 PCB. Since MIDI has no Opto-converter, the levels should be true TTL and I'm planning to use generic soundcard with Joystic/MIDI DB-15 connector which provides MIDI with TTL levels. The power should be +5V

A little doubt is a controller PROM. The original MT-32 has a display and some knobs on the face. Working inside E-20 this boars no need any controls and works "headless".

Unfortunately, I can't find a good photo of the "new" MT-32 PCB. The "old" PCB may be found there:

http://queststudios.com/smf/index.php?topic=1414.0

Can anyone provide a good photo of the "new/headphone" PCB of the MT-32 ?

The card was successfully revived. Thx to tnt23 !!

The missing parts were soldered back and viola! The card is working.

The main trouble was a LCD display with rare LCD controller SED1200, so tnt23
made a tiny "translator" with ATMEGA88 to the mainstream HD44780 command set.
This "translator" also donloads missing characters into HD44780 char generator.

Video:
http://www.youtube.com/watch?v=Pknr-oy8flI
(bad sound due to phone camera, sorry)

Photo set:
http://www.flickr.com/photos/46193097@N08/set … 57637506220566/

We are STRONGLY SEEKING for the original MT-32 case with original display and knobs,
perhaps with conpletely dead PCBs.

^ amazing!
please consider sharing that "translator" project, it could be useful in future repairs... 😀

keropi

http://sensi.org/~tnt23/sed1200emu/

^ awesome again, thanks!

The Roland E-10 keyboard contains this voice board too. It is revision 00 in my case, and has the same assy number as in these pictures. The socketed MT-32 ROM on this board says "2.0.0".
I hope to one day do the above project with my E-10. Not sure if my board is working though, that will be the first thing to check. I should compare it with my MT-32, both electronics and audio output. It looks to me like E-10 has the same synth board as E-20, but has a different CPU-board (left board/synth equal, middle board/cpu different, right board/power equal), based on the images referenced in this thread.

Image of the board found in my Roland E-10:

alec_v wrote on 2013-11-11, 20:06:

The missing parts were soldered back and viola! The card is working.

Some years ago, but I wonder how did you attach the MIDI port? By running a cable to the other board in the pictures, or on the same board?
What were the missing parts? I see an added 7805 VRM, a power plug, two pin headers, and a power plug, and the LCD parts. Anything else? Some small ICs in front of each midi ports on the back?
Anyone that knows something or want to guess is welcome to answer 😀

perhenden wrote on 2021-12-09, 19:56:

Some years ago, but I wonder how did you attach the MIDI port? By running a cable to the other board in the pictures, or on the same board?

First runs were done via onboard connector with TTL MIDI signals. The said pin connector used to be attached to another epiano control board sending MIDI flow.

What were the missing parts? I see an added 7805 VRM, a power plug, two pin headers, and a power plug, and the LCD parts. Anything else? Some small ICs in front of each midi ports on the back?

7805 voltage regulator, yes. This one gets rather hot, because in MT-32 it is mounted on the metal case for heat dissipation. I failed to source proper power switch so just soldered a wire jumper in place to always have the board powered.
Then DIN-5 MIDI connector and optocoupler, for external MIDI source.
Then a couple of TRS 1/4" jacks and op-amps with other components, for sound output.

MT-32 Service Manual was of great help, showing both schematic and PCB connections in great detail. So it was just a matter of finding the missing part on the schematic and installing it on the PCB.

Hello everyone!
Reviving the topic. As I've got a dead E-20 from the local flea market as well!
The instrument is cleaned and restored now. And I was dreaming that it will work as an MT-32 "out of the box". But it is not the case...
Connected to the PC by MIDI it does produce some melody. But it is complete cacophony (comparing to what it should be)...
So, it seems to me that the only destiny for the thing is to be "cannibalized" and converted into the another "Ghetto MT-32"

I have started to map all missing parts (have built an Excel table with everything). And ordered some 5 pin DIN females.
Next step will be to order the main bunch of components.

For the 1-st phase the plan is to populate the missing MIDI interface area. As well as audio output.
The front buttons and display will be postponed to later stage.

Here is the missing parts list (at least 99% of what I was able to trace).
What maybe I didn't mention - the "induction coil" (sorry, don't know the correct term in English) in the power input area...
That one I was not able to guess so far...

Sheff wrote on 2025-02-11, 15:18:

Here is the missing parts list

Nice! This will be useful for the next person:)

The E-20 is equivalent to a second gen MT-32, the E-10 might be a first gen. The E-30 is a 3rd gen (CM-32L with some extra features/instruments).

However, it looks like all 3 models use a different patch order than the MT-32/CM-32L, rendering them incompatible with the MT-32 for gaming purposes, despite having the same sounds. Only games which didn't rely on any internal tones would work, and there probably isn't too many of those.

Spikey wrote on 2025-02-12, 07:39:

use a different patch order than the MT-32/CM-32L

Would using a different eprom solve the issue? I'm thinking of taking the roms (copied) from a real MT-32.

Yes, I was also thinking about potential change of the ROMs. I 've even purchased 2 "beds" (or, "cradles") to put into the board.
As currently the ROMs are soldered to PCB. While I want it to be "swappable".

Reverb ROM is same as MT32, the sample ROM appears to be a revision of one is 2nd generation MT32 so all you should need is the program ROM of a 2nd generation MT32, which is conveniently already socketed.

Also, confirming the assumption of Spikey regarding the board version. In my case (E-20) it is a "second gen" board, with the headphones placeholder.