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Roland MT-32 CM-32L upgrades?

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First post, by SkyHawk

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There's a bunch of these having been sold on eBay

https://www.ebay.ca/itm/285243529321?hash=ite … ABk9SR8abkpSLYg

System Board view - https://i.ebayimg.com/images/g/JfcAAOSwI6tkQEbx/s-l1600.jpg

Seller claims to have "upgraded" MT-32s to the CM-32L PCM ROM and control logic.

I was under the impression that was not possible. I'm not interested in buying one of these, but I am very curious how this was done and what the implications are for compatibility of these devices.

I'd guess this is just a CM-32L system board dropped into an MT-32 chassis, but this guy appears to be selling many of these, so probably not? I do spy a headphone jack, so this particular listing at least is not an MT-32(old) board.

Reply 2 of 7, by keropi

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Interesting, I thought it was only possible to do in the newer version MT-32 with the headphone jack...

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Reply 3 of 7, by Tiido

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This is for 2nd generation MT32s without the PGA LA32 chip, for these you simply use CM32 or LAPC program ROM and burn a new sample ROM with the extra sounds and you get all the fun. You might have to solder a wire to bring in the highest address line to the sample memory chip. 27C801 and one wire should be all that is needed for that.

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Reply 4 of 7, by keropi

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Turns out the 2nd unit is just a 2nd gen mt32 without the headphone jack. Apparently they exist.

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Reply 6 of 7, by keropi

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This mod essentially turns a suitable mt32 to a cm32l , I doubt there are compatibility issues different from a real cm32l
it is nice to get the extra sfx and screen if you have a new-version mt32 , can't see any drawbacks to it (except the modification work needed)

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Reply 7 of 7, by terryfi

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Tiido wrote on 2023-05-26, 21:24:

This is for 2nd generation MT32s without the PGA LA32 chip, for these you simply use CM32 or LAPC program ROM and burn a new sample ROM with the extra sounds and you get all the fun. You might have to solder a wire to bring in the highest address line to the sample memory chip. 27C801 and one wire should be all that is needed for that.

Can anyone please provide steps to burn ROM and what pins to solder. I have a 2nd gen MT-32 on the way for this purpose.

I am reading the service manual in English and Japanese from here:
https://www.synthxl.com/wp-content/uploads/20 … e-notes-3rd.pdf

In the photo, seller has also labeled there chips as M32-L. EPROM IC28 PROG TONE connected to LA chip, IC37 PCM WAVE and IC13 REVERB ROMs. IC28 and IC37 have 32 pins but IC13 has 28 pins.

Based on your discussion my guess is that we need to replace the program ROM IC28 and sample ROM IC37 with 27c801 EPROMs and do the wire mod for sample ROM, am I correct?

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