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Hints, Tips and Solutions (Do NOT post requests for help here) If you have any useful general hints and tips for vintage technology repair and restoration, please share them here. PLEASE DO NOT POST REQUESTS FOR HELP HERE!

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Old 15th Jul 2020, 4:10 pm   #1
stevehertz
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Default Polarity swapping wall wart connector leads

I recently bought a wall wart style power supply that was advertised as being 6V DC with negative on the central pin of the connector, positive on the outer. On receiving the supply I looked at the polarity diagram on the label and it showed positive core voltage - not negative as I needed. However, the last 30cm of the DC connection lead comprised a second, 'added on' series lead. And as I suspected, that short lead was being used to switch polarity. So the unit was exactly as I wanted albeit with a 'misleading' diagram on the wall wart.

The point of this post being to say that such polarity swapping leads are available to make the most of your collection of wall warts and/or to save the hassle of having to cut and resolder the leads on to a replacement (non-moulded) connector. Now, I've done a quick search on Ebay and I can't find a source of such polarity swapping leads, but maybe I'm using the wrong search description. They must be out there somewhere!
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Old 15th Jul 2020, 5:46 pm   #2
Jolly 7
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Default Re: Polarity swapping wall wart connector leads

I don't recall having come across such wallwarts with a second lead for changing polarity.
I am used to interchangeable DC plug tips instead.
There must be a built in switch in the second lead I guess ? Can we have a picture of your wall wart please, or failing that the ebay item number. Thanks.
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Old 15th Jul 2020, 5:50 pm   #3
duncanlowe
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Default Re: Polarity swapping wall wart connector leads

It's actually easier to swap the wires inline than put on a new plug. Of course this polarity swap device is easier still. I use the technique to extend supplies too. First see if there's any marking on the figure 8 cable to identify the wires. If not use something to mark. Cut the figure eight cable and split the two cores. shorten one on one side, by say 20mm. On the other half shorten the other lead by the same amount. Using small heatshrink for the individual cores and larger for overall strip and solder ends together. The offset puts the joins in different places. You keep the moulded plug at the end, and get to choose where the join is.
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Old 15th Jul 2020, 5:55 pm   #4
G6Tanuki
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Default Re: Polarity swapping wall wart connector leads

In times-past, Maplin sold replaceable "drop-leads" for this sort of thing.

The wall-wart fed a 2-prong socket; there were then leads with a 2-prong plug [reversible] to connect to a range of jack-plugs to fit your desired load.

Similar things are easily found with a bit of Googlism. RS sell a power-supply with the sort of 'in-line-reversible' connector I mean - see

https://uk.rs-online.com/web/p/deskt...pplies/7263040

For simpler setups, there are loads of polarity-reversers available - as an example see https://www.songbirdfx.com/products/...nverter-cable/
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Old 15th Jul 2020, 7:13 pm   #5
stevehertz
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Default Re: Polarity swapping wall wart connector leads

Here's the seller's photos of the unit. There's nothing to see really, as the photo doesn't appear to show the second lead that does the polarity swapping. In the flesh it just looks like a male and a female concentric connector joined together about 30cm from the end male one. It's more versatile to me in the long run, I have a 6V/1A DC supply that can be a +ve or -ve centre pin unit. The label shows that the basic unit is +ve centre pin.
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Old 16th Jul 2020, 11:54 pm   #6
Jolly 7
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Default Re: Polarity swapping wall wart connector leads

@stevehertz: Thanks for the photo. I am attaching some photos of the DIY arrangement I use for both differing centre pin polarity and DC plug types. The cable came from an old Maplin adaptor that failed. Maplin also sold these cables and tips as separate spares till they closed down in 2018.
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Old 17th Jul 2020, 8:47 am   #7
stevehertz
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Default Re: Polarity swapping wall wart connector leads

Quote:
Originally Posted by Jolly 7 View Post
@stevehertz: Thanks for the photo. I am attaching some photos of the DIY arrangement I use for both differing centre pin polarity and DC plug types. The cable came from an old Maplin adaptor that failed. Maplin also sold these cables and tips as separate spares till they closed down in 2018.
I think I have that Maplin kit somewhere.
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