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Pin allocation on 4 pin 12 volt/5 volt power supply for external USB disk caddy?
Avoriaz
Posts: 39,110 Forumite
in Techie Stuff
Is there an industry standard for this type of power supply and pin allocation?
I have two USB disk caddies. Both use a 12 volt/5 volt power adapter with a round 4 pin plug that fits in the socket on the caddy. The plug is designed so that it can only be inserted one way. There is a small protrusion on the plug that matches a groove in the socket and 2 of the pins are slightly closer together than the other 2.
The pins are allocated to 12volt + and – and 5 volt + and –
However the pin allocation is different.
One plug has 12 volts where the other has 5 volts and vice versa.
I only discovered this when I used the “wrong” power adapter and the disk in the caddy started smoking slightly and is now dead. :rolleyes:
When I checked the pins with a voltmeter I discovered the voltage differences.
I had, presumably wrongly, assumed that the pin allocation would be the same.
An expensive lesson.
Here is a crude, but hopefully explanatory, view of the plugs looking head on. The view is far bigger than life size.
I have two USB disk caddies. Both use a 12 volt/5 volt power adapter with a round 4 pin plug that fits in the socket on the caddy. The plug is designed so that it can only be inserted one way. There is a small protrusion on the plug that matches a groove in the socket and 2 of the pins are slightly closer together than the other 2.
The pins are allocated to 12volt + and – and 5 volt + and –
However the pin allocation is different.
One plug has 12 volts where the other has 5 volts and vice versa.
I only discovered this when I used the “wrong” power adapter and the disk in the caddy started smoking slightly and is now dead. :rolleyes:
When I checked the pins with a voltmeter I discovered the voltage differences.
I had, presumably wrongly, assumed that the pin allocation would be the same.
An expensive lesson.
Here is a crude, but hopefully explanatory, view of the plugs looking head on. The view is far bigger than life size.
0
Comments
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There is no industry standard.0
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Thanks Conor.There is no industry standard.
That is so frustrating.
I am used to varying polarities on single voltage two pin or jack type power supplies and I always check those.
I just assumed that this 4 pin dual voltage power supply would be consistent.
The 250gb disk drive was fairly old anyway and probably near the end of its useful life. I had about 1,200 irreplaceable video files on it but fortunately I always make sure I have three separate back ups so it wasn’t a total disaster.
I have already done another back up to replace this one so I still have 3 copies of my files.0 -
That's the great thing about standards, so many to choose from....0
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The only thing common with todays power supplies, is they all output 3.3v, 5v and 12v.
12v travels along yellow wires, 5v along red, and 3.3v along orange. Black is ground for the relative voltage - ie: -12v, -5v or -3.3v.Everybody is equal; However some are more equal than others.0
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