at power supply contruction

[truenoteno]

i have made a basic power supply from 2 12v car batteries (to get +12,G-12), i have all the votlages correct, i plug it in and nothing happens, is there some sort of timing for the voltages ?

 

[Mosfet]

AT personal computer motherboard right?
Did you provide the Power Good signal [ +5 V] that appears when the other voltages are correct?
Here is a page that describes the common power supply connectors for AT & ATX:
https://www.pcguide.com/ref/power/sup/partsMotherboard-c.html
regards

 

[NaN]

Ironically i was just fiddling with one of my old AT power supplies.

To get proper +/- 12V, you often need to adequately load the 5V supply. To my surprise however, this loading is to about 5% of the rated supply power.

For me, i had a 200W power supply, and at 5V i had to load it to about 10W. Do the math and you see i need a 10W, 2.5 Ohm resistor! (( I didnt happen to have one lying around )).

With some make-shift temporary testing resistances, I was drawing nearly 2A though the 5V line before i got it up to 12V regulation!

Hope it helps...
:NaN:

 

[truenoteno]

did you make your own power supply for your comp ? or were you just loading it.

where would you put the load resistor ?

 

[Chippie]

where would you put the load resistor ?

Across the 5volt output.......

 

[stevez]

If what you did is attempt to wire two 12 v car batteries together they should be in series - with the + terminal of one connected to the - terminal of the other. The point where those connect will be neutral or ground, the free + will be +12 v and the free - will be -12 v. You should also see 24 to 26 volts across the free + and -.