Amigaz wrote on 2025-05-15, 09:01:

I have dug out my beloved Roland external MIDI synths from a very long sleep and am in the process to check that they all work O […]
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I have dug out my beloved Roland external MIDI synths from a very long sleep and am in the process to check that they all work OK.

It is a Roland SC-55MKII, a CM-32L and an MT32

From what I understand all of these need at least 9V to operate.
I have measured the voltage output on all of the PSU's and it's between 13-14V.

My question is ... is this (higher?) voltage safe to use or does it go down a bit during load?
I don't want to toast my precioussssss babies 😉

Somebody who actually knows with certainty (or can be bothered to check) will be able to confirm, but AFAIK these synths all run the power received through a linear regulator that brings the voltage down to what the unit actually uses. So, as long as the power received is consistently above 9V (what the regulator can handle and what is specced on the unit), AND the voltage isn't too high (which would cause the linear to heat up more), things should be fine.

Additionally, the type of PSU you have is probably unregulated, which means that voltage under load (actual use) will be lower than what is measure without load, but likely still above 9V.

So, assuming these PSUs are OEM Roland/Boss/Edirol (like the ACB series) ones from back in the day OR quality compatible ones (polarity, nominal voltage, current capacity), you should be fine. There is an official compatibility matrix.

That being said, you can get high quality, modern official switch-mode Roland/Boss/Edirol PSUs that are sold as official replacements. These will output 9V consistently and are will cause the internal linear regulator to generate less heat. If you chose to do this, or to get third party PSUs, be aware of counterfeit branded PSUs and low quality ones that may generate audible noise, RF interference (typical of low quality switch-mode PSUs) and possibly even damage equipment (in more extreme cases).

Please be very careful and bear in mind that Roland power adapters are (as far as I know universally) reverse polarity..

appiah4 wrote on 2025-05-15, 12:01:

Please be very careful and bear in mind that Roland power adapters are (as far as I know universally) reverse polarity..

Yes, I am aware of that. The Roland ones clearly show the polarity on the label on the PSU

Thanks

darry wrote on 2025-05-15, 11:13:

Somebody who actually knows with certainty (or can be bothered to check) will be able to confirm, but AFAIK these synths all run […]
Show full quote

Amigaz wrote on 2025-05-15, 09:01:

I have dug out my beloved Roland external MIDI synths from a very long sleep and am in the process to check that they all work O […]
Show full quote

I have dug out my beloved Roland external MIDI synths from a very long sleep and am in the process to check that they all work OK.

It is a Roland SC-55MKII, a CM-32L and an MT32

From what I understand all of these need at least 9V to operate.
I have measured the voltage output on all of the PSU's and it's between 13-14V.

My question is ... is this (higher?) voltage safe to use or does it go down a bit during load?
I don't want to toast my precioussssss babies 😉

Somebody who actually knows with certainty (or can be bothered to check) will be able to confirm, but AFAIK these synths all run the power received through a linear regulator that brings the voltage down to what the unit actually uses. So, as long as the power received is consistently above 9V (what the regulator can handle and what is specced on the unit), AND the voltage isn't too high (which would cause the linear to heat up more), things should be fine.

Additionally, the type of PSU you have is probably unregulated, which means that voltage under load (actual use) will be lower than what is measure without load, but likely still above 9V.

So, assuming these PSUs are OEM Roland/Boss/Edirol (like the ACB series) ones from back in the day OR quality compatible ones (polarity, nominal voltage, current capacity), you should be fine. There is an official compatibility matrix.

That being said, you can get high quality, modern official switch-mode Roland/Boss/Edirol PSUs that are sold as official replacements. These will output 9V consistently and are will cause the internal linear regulator to generate less heat. If you chose to do this, or to get third party PSUs, be aware of counterfeit branded PSUs and low quality ones that may generate audible noise, RF interference (typical of low quality switch-mode PSUs) and possibly even damage equipment (in more extreme cases).

Thanks for the detailed info.
They are all genuine Roland PSU’s
Now I feel safe to use them.

the 9V written on the bricks is only under the load equalling to the current written on them, i.e at 1A or 1.2A. Without load it is normal to get around 14V range reading, that voltage will drop when actually connected to the synth etc.

And as said before the devices these supplies are used for have a 7805 type linear voltage regulator in them and they'll operate from about 7.5V to 20V+, although as voltage increases their temperature will too as all the excess above 5V is burned as heat and the heatsinks in these things are pretty small.

These PSUs will read high when no load is attached, dropping down to spec when actually powering the device.