How do you test a AT power supply

[tylerden]

Anybody tell me if you have to jumper anything to test a AT power supply. When I turn power on now the fan won't come on and I read the voltage at the motherboard connection and get only 2 volts. Any help out there to tell if my power supply is dead or not. Thanks Barry

[toms111]

Un plug all connections to the mother board and to all drives. If the fan doesn't come on, its dead. Very often, what looks like a dead power supply is really a dead component. I don't know how it works, electrically but I assume that the power supply sees a short and refuses to power up. If the fan comes on with everything disconected, start with the mother board connection and no drives and see if it powers up. If it does, add one drive at a time until you determine what is bad.
Note: If it doesn't power up with just the MB connected, try removing all cards except the vidio and try again. Sometimes, a bad card can cause the motherboad to short out.

[This message has been edited by toms111 (edited 07-14-99).]

[Roy]

AT supplies require some load to start up, typically 20% of rated power on the =5V output. There are notes about this and other PC power connections at www.hut.fi/Misc/Electronics/circuits/power_from_pc.html (http://www.hut.fi/Misc/Electronics/circuits/power_from_pc.html)