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Unknown condition ATX SMPS repair - when should u power it up?
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lordvader88:
I have a 1200W PSU to repair, not sure what's wrong with it, bought as-is. So I haven't powered it with mains yet.

So nothing visibly wrong so far, (but lots of hidden stuff too) looking around inside the mains filter stage is fine, the dual rectifiers, PFC caps/mosfets/diodes seem fine in circuit. The main PWM mosfets seem fine. The various inductors/trans. I've checked so far seem fine to a DMM. I've applied 10Vdc in, and everywhere I checked so far seems about as I'd expect 10V to do. I haven't found the low-voltage supply area yet, I'll do that now (or play StarCraft 2 campaign on brutal).

There's a relay that's right before the 2 main PFC caps. In circuit it's switch side reads as 18ohm, it should be open, I'll have to pull that. It's a 2-sided PCB, maybe thats more for inrush current and I'm reading 18ohm from a current limiting thing, and then the relay would turn on to just close the switch after a few moments. Just remembered that trick from teardowns.


I have a current limiter lightblub setup, but I won't have an auto-transformer until June/july.

I haven't checked anything on output side yet. How safe should it be to turn it on now ?

There's a lot of daughter boards with various fets/controllers, and a 5V and 12V VRM sections for final output reg. I don't want to turn it on if I'm only doing more damage. Lot of work tho to pull and check the daughter board stuff at random.
Karlo_Moharic:
Unless there is some component that is clearly bad (burned or physically damaged) , just turn it on . That is the best way to check  weather there in any life in the damn thing or not.

Given that this is a computer power supply , before you plug it in , you will have to jump green and black wire on your main motherboard connector , because that is "power on" signal. For more detailed instructions just google how to power on atx power supply without motherboard.

Also if I'm not mistaken you were the guy that posted a question regarding PSU load test , I think I recommended you to buy some cheap shunt resistors off of ebay.

DO NOT conduct any type of load test before you make sure that PSU is running normaly without any load.

The last piece of advice I would give you is to not poke inside PSU with your fingers while it's pluged into outlet. To that effect, when you plug it out of outlet , make sure that main filter caps (large HV electrolytic caps right behind rectifier) are bleed. You can check this by putting voltmeter across caps terminals.
sokoloff:

--- Quote from: Karlo_Moharic on May 26, 2018, 08:33:35 am ---Unless there is some component that is clearly bad (burned or physically damaged) , just turn it on . That is the best way to check  weather there in any life in the damn thing or not.
--- End quote ---
Exactly.

Whoever had it last almost surely plugged it in. You're not saving an ancient artifact from possible damage here.
wraper:
Yeah, just power it up. If there was a serious failure on primary side, fuse should be already blown up anyway.
sokoloff:

--- Quote from: Karlo_Moharic on May 26, 2018, 08:33:35 am ---Given that this is a computer power supply , before you plug it in , you will have to jump green and black wire on your main motherboard connector , because that is "power on" signal.
--- End quote ---
Minor note: This does not have to be done prior to plugging it in. Perfectly fine (and what I'd do) to plug the supply in and later jump the green wire (pin 16) to ground to turn the supply on.
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