VOGONS


Roland MT-32 power supply.

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First post, by Baoran

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I just got my first MT-32 today and it came with a power supply from 1989. It is meant for the old 220V and we use 230V nowadays.
It is suppose to be 9V and 1000mah power supply and I measured output voltage as 14.28V without load using multimeter.
Is it safe to connect it to the MT-32 unit? I don't know how much voltage goes down when there is load and how good the voltage regulation is in the unit.

Reply 1 of 33, by keropi

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Yes it is safe - those old PSUs are unregulated and without load they output more voltage so don't worry about that.

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Reply 2 of 33, by bjwil1991

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I tested mine before hooking it up again after sitting in storage years ago, and it still works. Unlike the Commodore's infamous epoxy of death, the PSU still works extremely well (I was afraid the unit would stop working, but I checked everything inside the unit beforehand).

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Reply 3 of 33, by Baoran

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I just tested the unit for the first time. I assume it is normal to get really low volume when you connect headphones directly to it?
It will be couple days until I get audio cable for it.

Reply 4 of 33, by tpowell.ca

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Baoran wrote:

I just tested the unit for the first time. I assume it is normal to get really low volume when you connect headphones directly to it?
It will be couple days until I get audio cable for it.

Assuming you have a rev 0 device (no dedicated headphone output), then yes. You're getting line-level outputs, and its normal to hear very little on headphones.
If you can't wait, you could always stop by some local electronics store to pick up some cheap TRS to RCA converters. They cost next to nothing.

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Reply 5 of 33, by CrossBow777

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Was going to add that if you don't have a power supply for these, that a Sega Genesis or in your case a model 1 megadrive power supply will work. Yes it has more amps, but that isn't a problem. I was using my MT-200 and MT-32 for about a week or so with a sega power supply until I got actual Roland P120 replacements for both modules.

I also was lucky in that I was able to pick up the trs to 1/4" audio cables from Radio Shack when they were clearance them out for very cheap but obviously the adapters will work too as I use those on my mixer.

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

Reply 6 of 33, by Baoran

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Not really in hurry, I was just checking if it was working. So far I have tested doom and duke3d with general midi settings. (I know general midi doesn't sound right) and both give me sound.
Weird thing though setting leisure suit larry 3 sound to MT-32 causes the game to freeze when I launch it.
I should be getting the proper audio cable tomorrow or monday.

Reply 7 of 33, by Jo22

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I got my MT-32 with an universal power supply.
It's rated 9V, 1A. Without load, output voltage is 12,81v.

Not sure if this the ideal psu, but it works with my MT-32
(a model without a headphones jack).

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Reply 8 of 33, by CrossBow777

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Should be fine, the amperage and polarity are whats most important along with the voltage. All unregulated PSUs without a load are going to read higher than they are rated at. The Idea is that they maintain that voltage when there is a load pulling on them. Heck I have several sega PSUs that are 9v or 10v at 1.2 amp rated, and they are in fact generating 14.5 without a load. Then again, household current here in the states is basically 120v now as opposed to the 115 - 117 that was considered normal back then. In fact most of the outlets in my house actually read between 123 - 125 volts at any given time.

One of the reasons I've been switching to more modern day switching power supply bricks and or swapping out the voltage regulators with DC-DC converters instead.

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

Reply 10 of 33, by Baoran

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How much does input voltage affect output voltage of this kind of power supply? Back in 80s we had 220V and that is what the roland power supply is meant for and nowadays it is 230V and if I use multimeter to wall outlet, I get result of 229V.

Reply 11 of 33, by CrossBow777

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Basically the more voltage you put into something, the more heat has to be given off to drop it down. So I began to notice this more with my old Sega Model 1 Genesis. Been fine for years, and then I got a Sega CD model 1 to add to it. I noticed one day when I left the sega CD bios screen just up and running that after about 20min or so, the graphics started to form this snow pattern all over the screen. Odd thing was that it was only affecting certain graphics that were being generated by the Sega CD itself. This also started after I had just recapped it?! I checked everything and couldn't find any issues to cause this. Then I tested it with a model 2 Genesis and another model 1 genesis. And it didn't happen with those.

Finally tracked it down that my sega genesis itself was generating WAY more heat than the others for unknown reasons. Replacing the 7805s in it with higher amperage rated 7805s took care of the issue. Seems that the increased voltage from the PSUs was starting to burn out the original 7805s and they in turn were having to work harder to do what they needed to do and weren't providing as much current and voltage as they should be once they got to a certain point in heat. I've also swapped out the psu and use a modified gamecube supply now to power the genesis, sega CD, and the 32x from one switching power supply brick. More efficient and heat is virtually non existent on it now.

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

Reply 12 of 33, by bjwil1991

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That reminds me, I need to check my MT-32 for heating up chips and add heatsinks to them. I don't know if adding a fan would help, but, I think that'll be worth it to make the MT-32 run cooler.

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Systems from C64 to FX-6300.

Reply 13 of 33, by mockingbird

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Unrelgulated wall warts have a large capacitor in them after the four diode bridge rectifier.

If your brick is from 1989, then you should seriously consider cracking it open and replacing the cap.

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Reply 14 of 33, by Baoran

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I posted picture of it here https://www.vogons.org/viewtopic.php?f= ... 60#p659640
It is dated 0389.
I honestly don't know how to open one of those without breaking it.

Reply 15 of 33, by Jo22

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I forgot to add something important about universal power supplies.
Their Ampere (A) or Miliampere (mA) ratings do refere to the lowest voltage the PSU can offer.
So if you have one of these 1.5/3/5/7.5/9/12 bricks, the maximum amperage will refer to 1.5v.

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Reply 16 of 33, by Baoran

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I have been thinking of getting universal power supply for the unit just in case. My main problem is that when they come with different types of connectors, I don't actually know which one (if any) actually fits the MT-32 unit. Most of them seems to let me change polarity so that won't be a problem.

I found one universal power supply that lists the connectors like this:
2.5 mm monoplug
3.5 mm monoplug
3.5 x 1.35 mm DC plug
5 x 2.1 mm DC plug
5,5 x 1,5 mm DC plug
5.5 x 2.5 mm DC plug
New 5.5 x 2.1 mm DC plug
New 4 x 1.7 mm DC plug

Does anyone know if any of these is the correct one for MT-32?

Reply 17 of 33, by Baoran

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After few days the original mt-32 power supply started making buzzing noise, but the output voltage is still the same when there is no load. Any idea what might be causing that and if it is safe to continue using it?

Reply 18 of 33, by fitzpatr

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This goes for any MIDI module from Roland:

When in doubt, just buy a new one! Roland sells brand new, compatible AC adapters, PSB-120, for around $30 USD. The PSB-120 (For 110V-120V countries) is 9V, centre positive, 2A. It even has an inline power brick, rather than an on-plug one!

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Reply 19 of 33, by CrossBow777

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Yeap, that is what I eventually did. I used two Genesis model 1 power supplies until my two PSB-120s came in the mail. They are also switching power supplies so they are more efficient as well.

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