AT Power supply: how turn-on?

[zgouki]

Re: AT Power supply: how turn-on?

Hi again. I made the circuit that I told before, and it works! But another problem appeared....
Now, the PSU gives me the output voltajes 5 and 12 Volts for a second, and then this wires give me 0 and 0 volts for another second. This patron repeats all the time ----> 5...0...5...0...5 and 12...0...12...0...12, so I don´t know what can I do (I think that the motherboard-connectors (P8-P9

http://pinouts.ru/Power/MotherboardPower_pinout.shtml

) are the problem, but I don´t know how to connect them...)
I´m really frustrated...I need your help!!!
Greetings buddies.

[PCBONEZ]

Re: AT Power supply: how turn-on?

Some power supplies are designed such that if there is no current at all they turn off the voltage.
You may need to have a load on the power supply to keep the voltage steady.

My power supply tester uses two 10 ohm, 5 watt resistors...
... one each on 12v and 5v.
That might be a good size to try first.

As you intend to use this as a work bench power supply you may want to permanently connect some larger resistors (maybe 100 ohms) to keep it on with a changing load.
You want a larger (ohms) resistor to minimize current loss through the resistor but it must pass enough current to keep the PSU on with no other loads.

Experimentation will eventually find the best value. (ohms).

.

[kikkoman]

Re: AT Power supply: how turn-on?

You may need to have a load on the power supply to keep the voltage steady.
.

true. any old HD or CD/DVD drive usually works, too.

here's another thought: maybe you need to connect (gray) to (black) only temporarily.
like the front switch of a regular ATX PC. if you keep it connected, it cycles through on and off.
(although the control circuitry for this is located on the MB and the ATX PSU is permanently switched.)

since your PSU is a proprietary solution, I can imagine pretty much anything.

another one: (violet) may be a reset line. try what happens when you don't connect it to anything.

[PCBONEZ]

Re: AT Power supply: how turn-on?

I agree. Good point.
I suggested it might need a momentary switch earlier but dropped the subject when it seemed to be working.