Rewiring the DC plug to be centre negative

[NewcastleSAR]

Hi Folks..

I just bought a 5.2v 2.5A PSU for a piece of equipment that went on the blink. Connected it in but nothing happened so I though I had a dud PSU. I compared it with the original and lo and behold, I discovered that the original PSU is centre negative. The new one I have is centre positive.

Can I just cut the end of the new one and resolder it as centre negative?

Many thanks

p.s. Equipment still works. Tested it with another psu that is working

Declan

 

[alec_t]

Can I just cut the end of the new one and resolder it as centre negative?

Yes, if it's a standard DC power plug having only 2 connections.

 

[picbits]

Chances are the plug is not rewirable so just chop the cable itself, swap over the two wires and solder / heatshrink or use appropriate connectors.

 

[Roff]

Stagger the solder joints, cover each one with shrink tubing, the cover the entire job with larger shrink tubing.

 

[()blivion]

What I do rather than cut some where in the middle of the wire, is I cut the plastic off the actual connector and solder onto there. This makes a better looking product do to not having any seam anywhere in the wire. The process is...

(1) Cut all the plastic off around the barrel connector.
(2) Cut, strip, and clean the wire and slip on some heat-shrink.
(3) Solder to the back of connector.
(4) Cover the soldered area with some hot glue.
(5) When cooled, slip the heat-shrink over and heat it.

When you heat the heat-shrink, it re-liquefies the hot glue a bit making it flow into the contours and it smooths out really well. This essentially reforms a flexible plastic block around the barrel connector. Which ultimately creates a cord with no ugly seams and splices. Works wonders for tip-slip-ring style jacks also, since that is almost always the point where those end up breaking on me.

 

[JimB]

Or alternatively, is it possible to open the case of the new power supply and do the wire swap inside the PSU case?

When you said:

Connected it in but nothing happened

The thought occured to me that you have new killed the device you are powering due to reverse connected power.

JimB

 

[()blivion]

The thought occurred to me that you have [now] killed the device you are powering due to reverse connected power.

Read OP's first post again....

Hi Folks..

. . . :snip: . . .

Many thanks

p.s. Equipment still works. Tested it with another psu that is working

Declan

(I am not trying to be rude BTW, It was an honest and perfectly understandable mistake.)

 

[JimB]

Be as rude as you like!
I feel an idiot for missing that little snippet of info.

JimB

 

[Menticol]

Here is a graphical description of what the guys are telling you

View attachment 68641 View attachment 68642

View attachment 68643 View attachment 68644

View attachment 68645

Of course, reverse the polarity at step 4

 

[()blivion]

WOW that's... Wow. LOL, I usually don't bother to curve them, nor do I leave them without a cover. But yeah, otherwise that is pretty much exactly what I do. Maybe using a colored hot melt glue would make it look better? Not to suggest that it looks terrible as is.

If I could find the damn cord to my camera I would upload some pictures of my work for all to see.

 

[()blivion]

Found cable. . .

Charging camera/phone . . .

Taking pictures . . .

Uploading . . .

View attachment 68655 View attachment 68656 View attachment 68657

Note that in the first picture there is no seam anywhere in the cable. Of course I could have easily done this by installing a cable with a jack already on it into the cigarette lighter power adapter, but I didn't do this. Also note in the third picture the TRS phone connector is a 2.5mm unit, NOT 3.5mm. The one next to it is 3.5mm, and is just there for size reference.

 

[Menticol]

That's a wonderful job ()blivion!

I used to employ hot glue for the repairs, until I discovered the almighty shrink tubing. It's a bit expensive here, but the results are much better.

PS: The hot glue method remains for those who are too lazy to get shrink tubing, or those who ran out of it.

PS: The only thing I don't like about shrink tubing is having to de-solder the plug if you forgot to insert it on one end. Some form of "wrappable" shrink tube would be damn great.

 

[Menticol]

Maybe using a colored hot melt glue would make it look better?

You gave me an idea! what about putting a small LED and resistor inside the transparent glue blob? One of those ghetto style color-changing LEDs LOL

https://www.youtube.com/watch?v=is_AV7bGbT8

 

[mvs sarma]

In India we get a small cable called reversing able for such adopters.

 

[()blivion]

The only thing I don't like about shrink tubing is having to de-solder the plug if you forgot to insert it on one end. Some form of "wrappable" shrink tube would be damn great.

Yeah, that is really quite annoying. If you get used to using the stuff though then you almost never forget.

I had thought about wrappable heat shrink before, it would be cool. Maybe something like black tape that shrank? Where the sticky side cures with heat. Or maybe more like an epoxy/cement that chemically bonds to the back side... THEN you shrink it. I think the chemistry would be tricky. Glues and epoxy's don't like to be heated. The final thought would be just the heat shrink material that melts to it's self before it starts to shrink. But that is more unlikely.

As I understand in heat shrink works because they stretch it cold. It shrinks when heated because that was it's original size to begin with, it's just returning.

 

[Mr RB]

When I build stuff these days I put a bridge rect inside the device (and usually a voltage regulator) so for power i can use pretty much any plugpack that is around, AC, DC and any voltage high enough (so I collect 12v plugpacks).

Your "piece of equipment" seems to already have a protection diode so it would not be hard to add 3 more diodes and make it AC/DC compatible and insensitive to polarity.

Another tip when making equipment is to get the DC plug socket with the smaller inner prong (I think it's 1.8mm?) and that will generally fit all the plugs that you might have around on all your plugpacks.

 

[throbscottle]

Wow - impressed. I used epoxy putty to do this to a load of broken earphones. Like both your ways better

 

[()blivion]

OOPs!! Didn't see RB's post.

When I build stuff these days I put a bridge rect inside the device (and usually a voltage regulator) so for power i can use pretty much any plugpack that is around, AC, DC and any voltage high enough (so I collect 12v plugpacks).

I too have started to make a sort of "omni-power" collection that has unified most of my electronics. I make intermediate "jacks" that have a standard female barrel connector on one end, and whatever I need on the other. This way I can use any wall adapter, paired with my adapter, and that will power any project. Your way is decidedly better, unless you have equipment that you don't want to have to ever open. (Since it will say void the warranty.)

Wow - impressed. I used epoxy putty to do this to a load of broken earphones. Like both your ways better

Thanks. Yeah hot glue + heat-shrink also retains significant flexibility, which is important in cable longevity. It also looks a touch better when you use a proper heat source to set the heat-shrink, rather than whatever fire making device you happen to have in your pocket

 

[throbscottle]

Thanks. Yeah hot glue + heat-shrink also retains significant flexibility, which is important in cable longevity. It also looks a touch better when you use a proper heat source to set the heat-shrink, rather than whatever fire making device you happen to have in your pocket

Ah yes, but what if you like the look of brown, bubbly heat shrink?