A Question About Power Supplies

[cornemuse]

I made up a switch for testing bare outofthecase psu's, check voltages, etc.
What would cause a psu to come on for a ¼-½ sec or so & then shut down?? the fan does not even make one revolution, not on long enough to measure volts. Its a 'spare' & no big deal, I just wondered, , ,

-c-

(Not recycled, yet, , , ,)

 

[FordGT90Concept]

As in when plugging it into the mains? It's a self-test to demonstrate the UPS is functional. That said, it might be a function of the motherboard BIOS rather than purely the PSU (motherboard sees power, motherboard triggers self-test, motherboard triggers power-off-standby state).


Edit: Oh, now I get you. It's most likely shot, probably a blown capacitor. When a PSU is ordered to start via the correct wires, it is not supposed to go back off until the wires lose connection.

 

[Jetster]

No Idea what you're doing Are you measuring the voltage? Or just going by the fan turning because not all fans continue to turn? Some never turn unless there is a load causing heat

How about a pic of this switch you talking about

 

[Luke Whitton]

Could be a Capacitors.

Have you tried to continually switching it off and on a bunch of times?
If so, is their any noticeable difference with how long it stays on for/ how many revs the fan makes?
Only reason i ask that is because broken Caps can do funny things once they've warmed up abit.

 

[infrared]

If I've read your post correctly, you're trying to power up a computer psu and it's not staying on?

It could just be that it doesn't like running with no load on it. Voltage and ripple measurements with no load are a waste of time anyway, you need to see what it's doing with some load on it really.

 

[cornemuse]

If you 'jump' the green wire with a black (ground) wire on the 24 pin mobo plug, the psu should stay powered up till you disconnect them. This one does not.

I unsoldered the 'mating' socket from a bad mobo & cut out the appropriate portion of it, (6 pins worth), removed all but the conn to the green & one black, much easier to plug/unplug & soldered a power switch from junk comp case. (actually, I used a 'turbo' switch from a really old case, they stay on till a second push, power switches are momentary contact type)

Anyways, like I said, I am curious, thats all, , ,

I'm retired & have lots 'o' free time on my hands.

-c-

 

[Jetster]

If you 'jump' the green wire with a black (ground) wire on the 24 pin mobo plug, the psu should stay powered up till you disconnect them.


-c-

Just be aware that some PSUs when "powered up" dont spin the fans. But still provide voltage so you need a volt multi meter to verify they are running

 

[cornemuse]

This one = nothing, no 5, no 12, , , voltmeter connected, voltage starts to rise, then zero, 5 & 12.

Sent it to recyclers, , , ,

-c-

 

[sneekypeet]

If I've read your post correctly, you're trying to power up a computer psu and it's not staying on?

It could just be that it doesn't like running with no load on it. Voltage and ripple measurements with no load are a waste of time anyway, you need to see what it's doing with some load on it really.

This! Just plug in a fan via Molex or add in an old HDD to draw load from the PSU. Of course the PSU could be dead or have bad components, but without knowing the model of the PSU, it is hard to say if it is a newer unit that needs load to operate, or if it is some 300W OEM that has simply ran out of usable life.

 

[cornemuse]

PSU is history, , , ,