Recently my power supply stopped working so i bought a new one.
Its not branded or anything. Its a BlueDigit BPS2112.
It has a 20/24 pin connector however the white wire for -5v is missing. PIN 13.
The pc for which this power supply is intended is an old one. I don't even know the model number of the motherboard. So i'm not sure whether or not to connect this to the mobo. The broken down power supply DOES have the white wire.
So my questions are
1. Whether or not to connect this new power supply
2. What is the use of the -5v.
(if it is necessary, i was planning on making a seperate -5v circuit and giving the output to pin 13)
How old is your PC? Pre 2000 era? The -5V rail was made optional in ATX spec in 2002, and prohibited in 2003 so unless you have an ISA slot you have no reason to have a -5 V wire. It was removed because it was complex and not needed, most systems that now need -5 V generate it on the board rather than in the PSU since it is so rare.
I highly doubt you have a computer that "needs" a -5V rail, most of them haven't survived this long so i'd lilke to see a picture of the motherboard to make sure it really does because a homemade -5V circuit seems like a bad idea.
An AGP slot actually makes it more modern than most systems with ISA slots. AGP came out in 1996, ISA had been pretty much replaced by PCI by then so it is very unlikely you have an ISA slot. If you really really really insist that you need the -5V rail you can either look on ebay for an ancient PSU(not safe but probably safer than option 2) or you can make a circuit to create a -5 V rail from the +5V rail(not a good idea for anyone who isn't an electrician/electrical engineer or similar)
I would just try using the new power supply you have and see if it works, im 99.999% sure it will work just fine.