[judleroy]

I have a keling 54v 13amp unregulated power supply with. It is a toroid transformer and a small rectifier board. When I first fired it up and tested it about a year ago it read +53.4, -53.4v and the common was about 28v. Now the supply reads +55.4v and -55.4v or close to that. What causes the voltage to change like that? The reason I ask is my board is 55v and I need to keep the voltage below that. Is there a way to lower the output voltage by just a couple of volts. I'm also wondering if I can add a fuse somewhere to protect against over voltage and over current? Any help or advice would be appreciated. Thanks
Judleroy

[Al_The_Man]

If your mains supply happens to fluctuate, the output will also, which can happen at peak demand times of the day.
If you want to keep it down to below a certain level, the easiest way is to take a few turns off the toroid secondary, they are usually wound on last, ~2turns/volt.
Al.

[judleroy]

Thanks Al I new you would have the answer. Is there anything I need to no to keep from messing things up while taking off the windings? Do I have to take the plastic off the coil to remove the windings?
Judleroy

[Al_The_Man]

Do I have to take the plastic off the coil to remove the windings?
Judleroy

Yes, it can be rewound on or use electrical tape, but you may not have to remove all of the insulating tape as it does not take many turns to reduce it.
Just make sure you have the right secondary winding if there is more than one.
I have often wound on a separate auxiliary winding on top for 5,12 or 24v, whatever I needed at the time.
Al.

[judleroy]

There are 4 output windings off of the toroid. The toroid says they are blue-green-blue-green. The two blues together give me +54v and the two green give me -54v. The toroid says O/P: 1. Blue-Green and 2. Blue-Green. Would I take 4 windings from both #2 windings (blue and green) to remove 2 volts from the supply? Thanks Again
Judleroy