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Roland MT-32 power supply.

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Reply 20 of 33, by Baoran

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I was looking at roland PSB-230 EU at one site, but it didn't list MT-32 in the list of devices it is compatible with. Perhaps it isn't listed just because it is so old though.

Reply 21 of 33, by Dominus

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As far as my research went, it (psb-230) is compatible.

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Reply 22 of 33, by TheMobRules

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If I'm not mistaken both the PSB-120 and PSB-230 accept an input range of 100-240V AC despite their name (at the very least the PSB-120 does), the only difference being the plug type.

And yes, they're compatible with the MT-32.

Reply 23 of 33, by Mikity

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Just for the sake of posterity...
Here is the official list from Roland regarding which devices should use which power supplies (US only). Most of the ones we're interested in take 9 V and 1 or 1.2 A, meaning the PSB-120 is the best choice.
Interestingly enough for the MT-32 they recommend the smaller PSA-120S, which can only supply 0.5 A.

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Reply 25 of 33, by Jo22

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Dr. D wrote:

I have a need to run my MT-32 where there is no mains supply. I'm wondering if anyone has tried running it on 5V (USB)? I can't test right now, unfortunately. Thanks!

Uh, USB power sources aren't the most reliable ones, I'm afraid.
If the MT-32 has a 9v DC input (please double check), then why not using a a pair of 4,5v batteries instead (3LR12) ?

Running it directly off 5v, maybe requires bypassing the internal voltage regulator (which also protects the MT-32).
Personally, I would hesitate doing that, cheap USB power sources may have lots of noise/ripple etc. or can't keep the voltage fully stable.
Especially these USB rechargeable battery packs (or in new English speech "power bricks") are of variyng quality.
Some are very good, some aren't quite so good. Brands are no help either, since these devices are rebranded very often, I believe.

Anyway, maybe it is possible to use a generic 13,8v rechargeable battery with built-in solar charger ("power station" ?), not sure.
Since I haven't studied the MT-32 schematic yet, I can't recommend this. General speaking, though, a LM7805 voltage regulator can handle from ca. 7v up to ca. 35v input,
depending on other factors (heat sinks, power draw of the target device etc). Again, this is no recommendation. It's just my personal thought.
So better check the datasheets closely before trying this.

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Reply 26 of 33, by Dr. D

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Thanks Jo22 -- schematics don't seem to help. I wonder how long 2 4.5 v would last? Or one 9V?? I need 2 hours. None of my portable power bricks have 9v outputs, only 5, but according to the scope it's pretty good quality.

Reply 27 of 33, by Jo22

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Hi, not sure how long they last, I'm sorry. 🙁 I don't know how much Ampere (A) the MT-32 draws, either.
I have to check, but I believe an 3LR12 battery has got a capacity of 2,2Ah to ~6Ah (Ampere per hour) depending on the type (zinc, alkaline etc).
By cotrast, the average 9v battery has got 0,6Ah (expensive lithium models have got 1,2Ah or so).

Generally speaking, if you need a long battery life, you can also add lead-gel batteries to the list.
These are very stable and have a high capacity (ca. 7Ah to 15Ah). The gel types are also relatively service friendly
(they don't gas out so easily and can lay in a wrong position for a while without taking damage).
Me and my father used to use them to power CB and amateur radios (for charging, he has got a solar cell panel in the garden and a charger in the house)..
The downside is, that these batteries are very strong (extremely high short-circuit current) and can cause a house fire if shorted. 😉

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Reply 28 of 33, by yawetaG

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Be careful using lithium batteries (especially lithium-polymer), unless you add some circuitry that cuts the circuit when the voltage gets too low. They can be damaged (leading to risks of fire or explosion and a shorter lifespan) if they are discharged too far.

Reply 29 of 33, by Salient

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Or do what I once did. 😀
Working for 8+ years and counting now:

MT-32%20Ombouw%20FINAL%20%282%29.jpgOr do what I did 😀

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Reply 30 of 33, by bjwil1991

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That mod is pretty good. Does it charge with the cord plugged in the back, or am I incorrect on there?

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Reply 31 of 33, by CrossBow777

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bjwil1991 wrote:

That mod is pretty good. Does it charge with the cord plugged in the back, or am I incorrect on there?

Looks like his mod was to take the transformer out of the adapter and wire it inside the MT-32 connected directly to the 7805 +5 regulator. This way he can just use an infinity "8" shaped power cord to power it with and not rely on a separate adapter at all. Nice for ease of use...

But this isn't any more reliable than using the adapter was to begin with since the transformer can still burn out over time. I did try and use a DC-DC switching regulator in place of the 7805 inside mine, but it wouldn't even power on with one? So odd too because I've used these Traco DC-DC regulators in most of my classic consoles without any issues. But yeah, the MT32 refused to power on with the DC-DC switching regulator in place.

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Reply 32 of 33, by Salient

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Its not more, or less, reliable, but it's way more convenient indeed with just an 8-shaped power lead. 😀

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Reply 33 of 33, by darry

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Mikity wrote:

Just for the sake of posterity...
Here is the official list from Roland regarding which devices should use which power supplies (US only). Most of the ones we're interested in take 9 V and 1 or 1.2 A, meaning the PSB-120 is the best choice.
Interestingly enough for the MT-32 they recommend the smaller PSA-120S, which can only supply 0.5 A.

Is anybody actually using an MT-32 with a PSA-120S ? I was thinking of replacing my thirty+ year old ACB-120 with a modern switching PSU for safety and efficiency purposes, so I bought a PSA-120S because it is the suggested Roland/BOSS replacement, but I not sure anymore as the packaging for the PSA-120S makes a deal out its 500mA overcurrent protection cutoff and the MT-32 is, after all, rated at 650mA .

Is it worth trying to ping Roland about a thirty+ year old product ?

EDIT : Am I excessively panicky about the old ACB-120 ?