Center positive power supplies

[vigilante397]

This is mostly just for the sake of my curiosity. I've been building for about 6 months now, and when I first started I picked up a batch of five 12V 1A power supplies on eBay for about $1.50 apiece. The catch? They were center positive. I was new to pedals as I had pretty much only used multi-pedals previously that had their own special power supply, so I didn't realize center negative was standard. So what did I do? I wired all my pedals backwards   The main advantage here (aside from my cheap power supplies) was that I could use metal jacks on metal boxes without the infamous positive voltage to ground issue. Whenever I make things for someone else I of course make them center negative, so I keep a center negative power supply on hand to test them, but I've lost a couple diodes and an opamp or two because I forgot which way I wired a pedal and plugged in the wrong power supply   But I still use the power supplies and every pedal on my board (except my tuner, which I obviously didn't build) is wired backwards to take my center positive power supply.

So basically I was just wondering if I'm completely insane and am the only person in the world that does this, or if anyone else out there does it too?  

[deadastronaut]

firstly you are a cheap ass..

but hey if it works, sod it..

[Jdansti]

Yes, you are insane!   

An easier solution would have been to conform and buy some inexpensive replacement plugs for your power supplies and make them center negative.  You could also cut the cable and repair it in reverse to get the right polarity.  As it is, you'll eventually fry more stuff.

If you continue as is, label the ends of your power cables and your boxes with the polarity and check them each time you use them.

[GibsonGM]

  You could also cut the cable and repair it in reverse to get the right polarity. 

If you continue as is, label the ends of your power cables and your boxes with the polarity and check them each time you use them.

I have quite a few I've cut, reversed the wires, and labeled as such (BOLDLY).   A good habit to get into might be to double-check the polarity of these guys with a meter before putting them into service.  I always do.  Esp when I see the electrical tape below the plug >;o)

[Thecomedian]

I went through my entire life nt knowing that the symbols of (-)-C.-(+) meant positive center tap or negative center if it's reversed symbol. It probably didn't matter much because I never lost power supplies, but I could imagine people not knowing that and plugging in the wrong supply to the wrong pedal in a board if you've got multiple types and only that little symbol on the DC jack of the pedal to guide them.

I got ahold of 20 1$ DC positive pin wall warts, too. I figured at that time that it would be a nice cheap way to supplement providing power. As long as I don't sell them, I guess I'm okay (unless I wanted to be that nasty unethical salesman type and caveat emptor people so they have to rebuy stuff when they plug it in and fry something because of their lack of knowledge). Disturbingly, these things seem to consume power plugged in even with no load. I had one I was working with and left it alone in a power strip, and a few days later I pulled it out and it was hot and rest of the power strip surface was cool apart from the socket it was in, so it clearly came from there. Not sure if that's the fabled vampire power of all electrical equipment, or if it's just cheap manufacturing. I would hope a wall wart would take no power until a load trips the thing on..

[wavley]

  You could also cut the cable and repair it in reverse to get the right polarity. 

If you continue as is, label the ends of your power cables and your boxes with the polarity and check them each time you use them.

I have quite a few I've cut, reversed the wires, and labeled as such (BOLDLY).   A good habit to get into might be to double-check the polarity of these guys with a meter before putting them into service.  I always do.  Esp when I see the electrical tape below the plug >;o)

Yeah, I do this same thing, I've reversed quite a few wall warts in my day.

[GGBB]

  You could also cut the cable and repair it in reverse to get the right polarity. 

If you continue as is, label the ends of your power cables and your boxes with the polarity and check them each time you use them.

I have quite a few I've cut, reversed the wires, and labeled as such (BOLDLY).   A good habit to get into might be to double-check the polarity of these guys with a meter before putting them into service.  I always do.  Esp when I see the electrical tape below the plug >;o)

Yeah, I do this same thing, I've reversed quite a few wall warts in my day.

Ditto.  The ones I'm using now are 9.5V regulated 500mA Class 2 and nice and quiet that I picked for $5.95 each (I have three).  Not only were they center positive, but they had an oddball plug.  At that price for that quality, replacing the plug was a no-brainer.

[vigilante397]

firstly you are a cheap ass..

Very true It does work though, and I've never fried anything on my stage rig, just stuff I had built for other people and couldn't remember how I wired it

You could also cut the cable and repair it in reverse to get the right polarity.

I did do this with one of my cables (the one I use on my commercially purchased tuner), but at this point if I were to do it with all of them I would have to re-drill all of my pedals to take the larger plastic jack in order to use center negative.

If you continue as is, label the ends of your power cables and your boxes with the polarity and check them each time you use them.

My cables are all labeled so I know which is which, but ever since I fried an opamp I started labeling the boxes. I keep them labeled until they're finished, at which point if they're going to be for me I keep them center positive and they go on my board to avoid being mixed up with pedals to be sold, which are center negative. Definitely saves me the trouble of unscrewing a pedal to check how it was wired before plugging it in

I have considered building a regulated power supply for my board and have seen some schematics out there, but I haven't gotten around to it

[Jdansti]

Another option is to build polarity reversing adapters for your positive center pedals and make all of your wall warts negative center. Just leave the adapters plugged into the pedals. You'd do this with a male plug on one end and a female plug on the other, and wire the tip of one to the sleeve of the other (and vice versa). You only need an inch of wire between the plugs, so it's pretty small when storing the pedals. I made one for use with positive center laptop power supplies.

[vigilante397]

John, that is a rather elegant solution that doesn't require re-soldering anything

I think the main thing I'm gathering from this thread is that this is more unusual than I originally thought. I figured there had to be a couple people out there that do the same thing 

But I guess now (when school is not in session and work isn't very busy) is as good a time as any to build me a regulated power supply for my board and stop this silly center positive nonsense 

[Mark Hammer]

You can buy 2.1mm plugs and jacks that are different colours.  I would suggest that maybe you adopt a personal standard that when the pedal is wired outside pos, you use one colour, and when it is wired outside neg, you use another.  Same for the plugs at the end of the wallwart cord.  For that matter, you can set up each wallwart to be a 2-plug daisy-chain, say with a black and red plug to complement a black or red jack on your pedals.  Let colour be your guide and you won't accidentally plug the wrong things in the wrong places.

[vigilante397]

You can buy 2.1mm plugs and jacks that are different colours.  I would suggest that maybe you adopt a personal standard that when the pedal is wired outside pos, you use one colour, and when it is wired outside neg, you use another.  Same for the plugs at the end of the wallwart cord.  For that matter, you can set up each wallwart to be a 2-plug daisy-chain, say with a black and red plug to complement a black or red jack on your pedals.  Let colour be your guide and you won't accidentally plug the wrong things in the wrong places.

That is an elegant solution. I do enjoy color-coded things. What I currently do is similar: for center positive pedals I use metal jacks (which we all know don't work with center negative) and for center negative I use plastic. The only reason I fried a pedal was because it was a weird box that only a plastic jack would fit on but I still wired it center positive. I saw the plastic jack and figured it was center positive

[Liquitone]

I do build a lot of pedals using positive center. It's because for the ones that use 24vdc, Electro-Harmonics 24vdc powersupplies are good, easily available and not expensive, and they all have 2.5mm positive centre.
For negative center I use those small isolated Lumberg 2.1mm DC-jacks and for the positive center I use metal DC-jacks, so It's easy to see, as the metal will be connected with the ring and the enclosure, so it has to be positive center.

[vigilante397]

I do build a lot of pedals using positive center. It's because for the ones that use 24vdc, Electro-Harmonics 24vdc powersupplies are good, easily available and not expensive, and they all have 2.5mm positive centre.
For negative center I use those small isolated Lumberg 2.1mm DC-jacks and for the positive center I use metal DC-jacks, so It's easy to see, as the metal will be connected with the ring and the enclosure, so it has to be positive center.

I'M NOT THE ONLY ONE!!!

But still, I already etched my PCBs for Tonepad's "Pedal Power" and am just waiting on a Tayda order to finish them up (I need 2 to power my whole board). As soon as I get those running I will make the switch to center negative, I promise