Hi,
I've got an ATX computer PS pulled from an old computer.
I know that 2 of the 20 pins on the ATX power plug have to be jumpered in order for the thing to power up .. not sure which ones .. was it
13-14? ... Also, after those are jumped, what turns on the supply? Normally, there's a push button on the computer which goes to a 2 pin header on the MB, which I assume sends some sort of "power up" signal to the ATX supply ... how do I fake that out?Thanks,
Bill
See
For a schematic of an ATX supply. We owe Pavel Ruzicka for taking the time to reverse engineer it. The info you're looking for is in the theory of operation on the site.
The start up line 5V start bus is a separate tiny supply that is running whenever the computer is plugged in (and turned on) It shares the input rectifier and filters with the main supply but is otherwise totally independent. A little three terminal regulator handles the output.
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He probably needs a minimum load on the PS output,too,most likely the +5V line.
-- Jim Yanik jyanik at kua.net
Possibly. The ATX diagram is representative of the type. In this particular one both the +5 and +12 / -12 are referenced back to the PWM via a voltage divider, which would suggest one or some combination of supplies might need some minimum load to regulate properly.
Hopefully he understands how dangerous the input circuits can be . . . never mind the outputs.
The schematic does show some (minimal) load resistors on the outputs.
A good basic info on switching supplies:
A better text on switching supplies with instructions on starting an ATX and using a dummy load on the +5 supply:
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I think CompUSA sells a PS tester. This gets by all of those wiring and switch problems. It is only about $20.00
What more is there than jumpering the Power_Supply_On wire to ground with a load on the output?
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That's pretty much all there is to those little cheapie testers... A little box containing a minimal load, some LEDs that give a go//nogo indication of all the voltages, a switch that lets you turn the PS on-off from the box and an instruction sheet that was written by a Chinese housewife and translated into English by a Russian schoolboy.
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