Yes, unloaded PSU will read high.

I like these for powering Roland audio hardware.

https://myvolts.co.uk/product/84651/myVolts_U … -ve_2.1mm_2.5mm

Lostdotfish wrote on 2025-03-30, 18:10:

Yes, unloaded PSU will read high.

Thank you for the respond, Lostdotfish.
Is 15V within expected values? Or it's still too high for a unloaded PSU?

BOSS still makes power supply adapters which are compatible with old Roland synths.

I'm EU based, so I'm using a PSA-230S for my SC-155. The model number differes slightly in the US, I think.

Bondi wrote on 2025-03-31, 07:57:

Lostdotfish wrote on 2025-03-30, 18:10:

Yes, unloaded PSU will read high.

Thank you for the respond, Lostdotfish.
Is 15V within expected values? Or it's still too high for a unloaded PSU?

Measure it in operation if you're concerned. Take the cover off the SC55 and meter the incoming voltage while it's powered on.

My original (UK 240V) adapter reads 12.4v unloaded.

As Joseph said, grab a Roland adapter if you’re worried https://www.rolandus.com/assets/press_media_r … dapterGuide.pdf

zuldan wrote on 2025-03-31, 10:09:

As Joseph said, grab a Roland adapter if you’re worried https://www.rolandus.com/assets/press_media_r … dapterGuide.pdf

Yep, I dislike messing around with step down so would probably replace it.

I used to run my MT32 and SC 55 off a Sega Mega Drive 1 power pack (chunky linear 10v center pin negative PSU). It was fine.

I'd seriously consider the USB C PD device above though. Keeps it nice and easy moving forward.

Bondi wrote on 2025-03-31, 07:57:

Is 15V within expected values? Or it's still too high for a unloaded PSU?

Bondi, thats normal, old unregulated AC adapters often display a higher-than-stated voltage reading when measured without a load, but this voltage drops to the rated value when a load is applied, which is a characteristic of unregulated power supplies.

But anyway I recommend to replace adapter to new switching power supply, which just more energy efficient.

When I checked old Nintendo Entertainment System adapter it showed me wrong voltage too without load.

Thank you to everyone who responded! Will see what it reads when loaded and also consider a different PSU.

The original Roland ACI-100C power adapter that came with my SC-55 also reads 15V when not connected to a load, so it's perfectly normal. Same setup as yours, 230V mains -> 115 after step down -> Power brick.

In any case, the SC-55 uses linear regulators internally, so it wouldn't matter much even if the input voltage was slightly higher than expected.