+/- 18v DC_PRT ?? understanding Power supply .

[jeremiah goike]

Hello,
I am attempting to modify a small Yamaha MS101-4 powered studio monitor/powered speaker.
I need to make it run on 12VDC battery power and It currently takes only AC power.
The internal ac/dc power supply puts out +24VDC with ground and also +18,-18 with ground.
I am proficient enough to implement 12VDC DC to 24VDC DC step up and also to find something for the +/- 18VDC BUT....

There is a additional pin that is labeled "DC_PRT" and I don't know what that means.
See photo.

I am hoping someone here can fill me in on this and possible coach me on what to do with that pin.

Also, if someone knows the 2 different series 'molex' style connectors used that would be amazing!

[fzabkar]

DC_PRT = DC Protect ?

Power amps sense the presence of DC on their outputs and go into protect mode if it exceeds a certain threshold. Usually there will be a protection relay.

[jeremiah goike]

Ah, thanks DC protection, that makes sense.

Curious how I should deal with this as I am hacking together a way to run this speaker on DC only and remove this ac/dc power supply.

I wish i knew someone I could just  hire for this project!!

[DrGeoff]

For a project like this, two immediate solutions spring to mind.
1) Get a small inverter and continue to power the speaker off the mains from the inverter. No mods needed.
2) Rather than attempting to redesign the power supply, refit a new amplifier that runs from 12V. Probably a class-D amp and a simple preamp/input circuit. Then you can eliminate the old power supply completely and replace the innards with something simpler.

[jeremiah goike]

Those are not bad ideas, thanks.
I'm afraid the inverter would likely introduce unwanted noise into the power.
A 12v amp would loose functionalities and likely quality of the internal amp which has tone controls and multiple balanced and unbalance inputs, it would be tough to emulate or retrofit while keeping those functionalities