AT Power Supply
(View looking into pins of plug)
Pin number |
Description |
Typical Colour* |
| 1 | Power Good# | Orange |
| 2 | +5V | Red |
| 3 | +12V | Yellow |
| 4 | -12V | Blue |
| 5 | 0V | Black |
| 6 | 0V | Black |
| 7 | 0V | Black |
| 8 | 0V | Black |
| 9 | -5V | White |
| 10 | +5V | Red |
| 11 | +5V | Red |
| 12 | +5V | Red |
NOTES:
*The colours indicated are only as a guide, there is no standard colour convention.
#The power good line will become high (+5V) shortly after switch on, when the supply outputs have stabilised.
When fitting the connector to the motherboard, it is vital the two plugs are inserted "blacks together".
Unlike the later ATX supply the AT supply will usually start up with only it's internal cooling fan as a load. As with many switch mode supplies, regulation is best when they are loaded to at least 10% of rated power.
For a typical supply, this load can be achieved by connecting 4 paralleled 4R7 power resistors into a convenient drive power connector (across the 5V rail, between black and red). If the test is to last more than a couple of seconds ensure adequate heat sinking has been provided.
AS WITH ALL SWITCH MODE PSUs, THE AT SUPPLY IS POTENTIALLY VERY DANGEROUS. DO NOT ATTEMPT THE PROCEDURE OUTLINED ABOVE UNLESS YOU ARE SUITABLY QUALIFIED.
IT IS INADVISABLE TO EVER REMOVE THE LID OF THE SUPPLY AND ATTEMPT A COMPONENT LEVEL REPAIR. WITH A NEW SUPPLY COSTING LESS THAN A COUPLE OF PIZZAS IT'S JUST NOT WORTH IT!
