Power supply always on (switches do nothing)

[JoeStrout]

The cab I bought came with a power supply that seems pretty decent, except for one big flaw: the switches don't work.  As soon as I plug it in, it comes on and supplies power, regardless of the switch state.

This PS has switches on both the front and rear of the unit.  According to the instructions in the label, either one should work as long as the other one is off.  But even when I turn them both off (or any other combination — I tried all four), the PS is on.



I suspect that is because of this "Remote switch" also mentioned on the label.  There is a big mess of wires coming out of this thing, and some of them are joined together with wire nuts.  I suspect that some of those are intended for a remote switch, and maybe the way they're joined together means "always on."  But before I start experimenting, I thought I'd see if anybody here happens to know off the top of my head what colors (or other clues?) I should be looking for.

(I did find the vendor's site, but couldn't find any manuals or spec sheets there.)

The other (less crucial) issue is that the spread between the 5V and 12V outputs is only a bit more than 5V.  There is a "5V Adjust" knob on top of the unit, and when I crank that up to where the 12V line hits 12V, the 5V lines are over 6V.  And in the other direction, when I adjust the 5V lines down to 5V, the 12V lines read a little over 10V.  Probably not a major issue, but thought I'd mention it in case somebody says "oh yeah, that, all you have to do is..."

Thanks,
- Joe

[big10p]

Not seen a switcher like this before, but I suspect you're right about the wiring for the remote switch being permanently connected. You'll probably just have to trace the wires on it and see where they go.

As for the other issue, be aware that switching power supplies can't usually regulate the voltages on the different rails unless there's a significant load on the +5v rail. If fact, some switchers automatically shut off if no load is detected on +5v.

[lilshawn]

only the 5 volt is watched during regulation. not the 12 volt.

in order to get a proper 12 volts, you need to load down the 5 volt line. this will bring up the 12 volt line.

i haven't the foggiest why your supply stays on. perhaps someone has messed with the insides to keep it on.

[mgb]

so according to the sticker on that supply, the wires for the remote power switch are brown,black,blue and white.

if the front switch has to be off for the rear switch to be used and vice versa and then both of those have to be off for using the remote switch.
then probably the remote switch has to be off in order to use either the front or rear switch.

I would assume that in the bundle of wire nutted cables you speak of, Brown is wire nutted to Black & Blue is wire nutted to White.
if so, open those connections and tape the wire ends to prevent them shorting or touching.