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Roland MT-32 (old) display question

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First post, by RetroNoob

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Should I bother looking for a replacement screen for my MT-32 (Old)?

The photo is a bit over bright for what I actually seen in person. It's readable, but there is a strong glow around the info, not just the info glowing, like I see in photos online.

As far as I know there's no contrast/brightness settings for the MT-32.

From other photos I've seen on the internet, it shouldn't glow as much as this?

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Last edited by RetroNoob on 2019-06-20, 09:42. Edited 1 time in total.

Reply 1 of 21, by keropi

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something is definitely wrong - maybe some simple component like a resistor is burned and the screen gets too much voltage or something... did you open the unit? maybe some component looks bad?

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Reply 2 of 21, by RetroNoob

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No, I haven't opened it up yet. I didn't really want to, unless there was something wrong.

I guess I'd better now.

I don't suppose you know where to get a replacement display from, that doesn't cost an arm and a leg?

Reply 3 of 21, by keropi

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there is a project to replace the original lcd screen with a modern one: http://sensi.org/~tnt23/sed1200emu/index.html
other than that I don't know any other sources...

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Reply 4 of 21, by Spikey

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Is the sound still working correctly? I've had weird contrasts on the LCD when I had an unsuitable power supply attached, or when I had a correct power supply with the polarity reversed.

Reply 5 of 21, by Jo22

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The power supply question is a good one. If the PSU is a cheap "modern" switching type from the local electronics store or super market, then I'm not surprised. 😉

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Reply 6 of 21, by Spikey

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I have legitimately thought the same thing as the OP, only to listen and the sound was messed up. I have moved back and forth between the US and Australia several times, having moments where I have repurposed household adapters to use for an evening, some times working fine, some not so well 😀

Reply 7 of 21, by RetroNoob

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keropi wrote:

there is a project to replace the original lcd screen with a modern one: http://sensi.org/~tnt23/sed1200emu/index.html
other than that I don't know any other sources...

Thanks, I guess I might have to learn more about that.

Spikey wrote:

Is the sound still working correctly? I've had weird contrasts on the LCD when I had an unsuitable power supply attached, or when I had a correct power supply with the polarity reversed.

Yes, the sound works fine. The polarity is fine - negative centre.

Jo22 wrote:

The power supply question is a good one. If the PSU is a cheap "modern" switching type from the local electronics store or super market, then I'm not surprised. 😉

I guess the PSU is one of type you mention, but I've the same problem with the original Roland PSU with a 240V > 100V.

Spikey wrote:

I have legitimately thought the same thing as the OP, only to listen and the sound was messed up. I have moved back and forth between the US and Australia several times, having moments where I have repurposed household adapters to use for an evening, some times working fine, some not so well 😀

Without swapping all the caps, I feel it's just the screen has started for fail. I've now come across other screens on other people's MT-32, that look as if they're getting to the same stage as mine is.

Reply 12 of 21, by RetroNoob

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Sorry for getting this going again after so long.

I never did get a replacement screen, because it turned out, it didn't match up anyways.

I have recently managed to get a REAL Roland ACB-240 No.12449564 PSU, that is the spec that the MT-32 needs., and works here in the UK.

The screen still has the same problem. So it's nothing to do with the PSU.

I guess I'm going to have to look into figuring out what the Cap replacement needs are.

Reply 13 of 21, by detalite

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I think that resistor responsible for contract is R44 27k (may vary betwen versions). It is connected between ground and pin V_LCD. I suggest to replace it with 50k potentiometer.
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Reply 14 of 21, by Salient

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I just unboxed my second, virtually unused, MT-32 I still had at the attic to check this out and guess what, it also has the bright-glow-phenomenon, with all PSU's i checked.
My other, somewhat beat-up and (ab)used all the time and modified with a crude self-built built-in power supply, is just fine. 😀
Sound is ok on both machines though.

I'm going to look into that resistor but I do feel kind of sorry for the device since it's immaculate still, both inside and outside, so there is a small chance I just leave it like this.

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Reply 15 of 21, by CrossBow777

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It really does surprise me that a modern OLED screen isn't already available for the MT-32. They appear to have OLED replacements for nearly every other major Roland synth that was in use in the 80s - 90s and I would think that the modules were popular enough that there would be a demand for replacements?

I've also wondered if the screens used in the MC-50 and the MT-100 are the same type and if those could be salvaged? In fact, now that I think about it, I think I found someone that made or makes a replacement OLED for the MC-50?

If any component is at fault, it would likely be on the LCD board itself as I believe the driver and pretty much everything is on that LCD board. I think only the data lines and power come from the SIP style ribbon cables?

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Midi Modules: MT-32 (OLD), MT-200, MT-300, MT-90S, MT-90U, SD-20

Reply 16 of 21, by cyclone3d

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CrossBow777 wrote on 2020-06-29, 17:18:

It really does surprise me that a modern OLED screen isn't already available for the MT-32. They appear to have OLED replacements for nearly every other major Roland synth that was in use in the 80s - 90s and I would think that the modules were popular enough that there would be a demand for replacements?

I've also wondered if the screens used in the MC-50 and the MT-100 are the same type and if those could be salvaged? In fact, now that I think about it, I think I found someone that made or makes a replacement OLED for the MC-50?

If any component is at fault, it would likely be on the LCD board itself as I believe the driver and pretty much everything is on that LCD board. I think only the data lines and power come from the SIP style ribbon cables?

Why would you want to take a screen from an MT-100 unless it is dead? The MT-100 is an MT-32 with sequencer.

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Reply 17 of 21, by CrossBow777

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cyclone3d wrote on 2020-06-29, 18:10:
CrossBow777 wrote on 2020-06-29, 17:18:

It really does surprise me that a modern OLED screen isn't already available for the MT-32. They appear to have OLED replacements for nearly every other major Roland synth that was in use in the 80s - 90s and I would think that the modules were popular enough that there would be a demand for replacements?

I've also wondered if the screens used in the MC-50 and the MT-100 are the same type and if those could be salvaged? In fact, now that I think about it, I think I found someone that made or makes a replacement OLED for the MC-50?

If any component is at fault, it would likely be on the LCD board itself as I believe the driver and pretty much everything is on that LCD board. I think only the data lines and power come from the SIP style ribbon cables?

Why would you want to take a screen from an MT-100 unless it is dead? The MT-100 is an MT-32 with sequencer.

Quite right and I should have been more clear. I meant salvaged from otherwise dead units. And I meant it more as a question on if the same screen in the MT-100 is the same used in the MT-32. I assumed they are because as you said, the MT-100 is an MT-32 with built in sequencing. I wasn't suggesting they be pulled from working units.

Also I was wrong about the possiblity of an OLED solution for the MC-50..it was the MC-500 I was thinking of and I still wonder if those screens are the same used in the MT-120 and MT-200?

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Reply 18 of 21, by Retro-Rabbit

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I've got an MT-100 and I can confirm that the MT-100 display is not the same as the SED1200 display used in the MT-32

The display on the MT-100 is connected to the PR-100 half of the system. An MT-100 is literally an MT-32 stuffed into the bottom of a PR-100 with an internal midi connection.
The LCD display ribbon cables that are on the MT-32 are not populated, and I'm working on adding a 20x2 OLED (using the above SED1200EMU mod as a starting point) in where the Quick-Disk drive is. Because who doesn't want to see "Insert Buckaziod" when playing SQ3. Also adding a usb floppy emulator as Quick-Disks are hard to find and not affordable when they do pop up. Famicom Disk system disks wont work as they are about 1cm too long where the 'Nintendo' logo is. This was done by Nintendo as copy protection to prevent use with actual Quick-Disks, which was easily bypassed with an unfolded paperclip and some tape.

Reply 19 of 21, by Thermalwrong

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If you find out how to do that, I'm keen to try that on my big old MT-100 too 😀

I do wonder why use a USB floppy emulator though, since it's not really a General MIDI device, is the floppy support good for recording, or playing back? I never tried that on mine, I don't have any quick-disks, but I also expect it wouldn't work.