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​PSU go to self-protection after desoldering motherboard's wires Answered

Computers' PSU are very convenient power source, which can be used in numerous application. Usually such applications don't need its wires connected to motherboard. Four times I observed issue, when different working PSU went to self-protection after desoldering bunch of motherboard wires. Even cutting wires, not desoldering them, produced similar issue. I mean PSU went to self protection, when after switching on it works during a few seconds and than it automatically switched off.

What can be the reason of such issue and how it could be fixed?

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Orngrimm
Orngrimm

11 months ago

It is not self-protection, but Self-Poweroff.
See, a PSU needs a certain minimal load applied to stay on.
If you have the PSU on but dont pull a bit of power on 5V, the PSU thinks there is nothing connected at all and switches off.
Check https://www.electronics-tutorials.ws/blog/convert... at "Testing the Power Supply" for a connection-Diagram.
I normally use a 10W 4.7Ohm resistor.

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Vaster
Vaster

Reply 11 months ago

Thank you, Orngrim and Downunder35m, for your reply, correction and advises. Nevertheless, why bunch of wires cutting or soldering off pass PSU to Self-Poweroff state? Any ideas?

>I normally use a 10W 4.7Ohm resistor.
Loading of 12 V, or 5 V output by 9 Ohm resistor don't return PSU to working state in my case.
I can do this only by grounding inputs of power supervising IC, but such solution is not too nice. I'd prefer to find something safer.


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Downunder35m
Downunder35m

11 months ago

Look up PSU to power supply or PSU to battery charger.
The green wire needs to be pulled down and you need a load on the 5V rail.
In the most basic form just add some break light from your car in the 5V line and you get a power indicator for free.