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Old 01-12-2017, 06:30 PM   #21
Drack
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Default Re: Fortron 200-50SNV(PF) SFF - dead, no 5VSB

This is what happens with this micro atx PSUs, they are so small that you have to take everything out to get to one cap, I'm working on a p3 PSU those are half the size than yours is, was a bi... to recap.
Still dead btw no voltage just 5vsb

Last edited by Drack; 01-12-2017 at 06:33 PM..
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Old 01-12-2017, 06:41 PM   #22
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Default Re: Fortron 200-50SNV(PF) SFF - dead, no 5VSB

I found out that the 240k resistor is burned - reads as infinite resistance.
But it's 1W. I only have 300K 1/2W. Is it safe to replace the faulty one?
And there is other option - I have 3 resistors x 80K 1W. But there is absolutely no space for this. It's really rare to find resistor with so big value and wattage.
Is this 240k? The color code is somehow... strange... But this resistor connects pin 3 of the IC to the diode bridge, so it has to be the right one. But it's not marked with the same number as in the schematic. Neither the resistor, nor the capacitor are with the same numbers, as in the schematic.
P.S I intend to cut the case of the PSU, because all the crap Im going to do will not fit inside. I made 240K by soldering 3x80K.

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Old 01-13-2017, 03:58 AM   #23
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Default Re: Fortron 200-50SNV(PF) SFF - dead, no 5VSB

Replaced the resistor with 3x80K and the capacitor with brand new 47uF/63V
The PSU powers up. I will test it.
But neither there is space for the resistors, nor for the capacitor. I will cut the back of the case. Usually, no one opens the computer and touches the live parts, when the computer is plugged into the wall socket.
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Old 01-13-2017, 04:49 AM   #24
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Default Re: Fortron 200-50SNV(PF) SFF - dead, no 5VSB

"Usually"

Maybe not, but it does happen.

Not a great idea. Get the proper resistor and don't turn things into deathtraps!
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Old 01-13-2017, 05:11 AM   #25
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Default Re: Fortron 200-50SNV(PF) SFF - dead, no 5VSB

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Not a great idea. Get the proper resistor and don't turn things into deathtraps!
I already did it. For safety reason, I've covered both the resistors and the new capacitor with heat shrink tubing.
The biggest problem is that if this happens again, again I will need to completely take apart the PSU.
The biggest problem is that brand new capacitors don't fit inside the case. I've tried 35, 50 and 63V. None of these fits inside.
Seems like the capacitors inside are special order(sh... one) If there was enough space, the slight difference in the dimensions won't matter, but in this case...this is the best I can get..

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Old 01-13-2017, 06:57 AM   #26
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Default Re: Fortron 200-50SNV(PF) SFF - dead, no 5VSB

Okay, but seems like this PSU has killed the mobo or there is problem with the mobo. I really don't know where this computer was stored, because it was extremely dirty and even there was some corrosion in the PSU.
I've tried the mobo with other PSU(tested all fine and worked with other mobos). The mobo randomly powers on and off even with disconnected power switch and neither the power switch itself, nor the pins on the mobo for power on work.
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Old 01-13-2017, 12:33 PM   #27
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Default Re: Fortron 200-50SNV(PF) SFF - dead, no 5VSB

Maybe a corrosion issue on the motherboard if there is other corrosion in the PC.

If you have schematic, you could check the power button circuit, maybe corroded pull up resistor leaving the button input in a floating state or a faulty transistor there. Could be anything.
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Old 01-13-2017, 12:43 PM   #28
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Default Re: Fortron 200-50SNV(PF) SFF - dead, no 5VSB

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Could be anything.
I know. The PSU has perfect voltages - 3.4V 11.75V, 5.1V, 5.05V - StandBy. It's alive. I also tested the mobo with another PSU - the same. The mobo refuses to power on or loops between on and off with no reason.
Seems like the PSU fried the mobo or it's just a coincidence.
I will leave it that way. Better to replace the mobo. No one knows how much more problems there could be.
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Old 01-13-2017, 01:19 PM   #29
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Default Re: Fortron 200-50SNV(PF) SFF - dead, no 5VSB

Great job fixing the PSU!! Too bad the mobo didn't make it though.
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Old 01-15-2017, 12:35 PM   #30
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Default Re: Fortron 200-50SNV(PF) SFF - dead, no 5VSB

Have you checked for shorts on the Mobo, maybe a shorted FET, dead Southbridge, have you bent the board? That worked for my old Biostar p4 mobo
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Old 01-15-2017, 02:02 PM   #31
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Default Re: Fortron 200-50SNV(PF) SFF - dead, no 5VSB

Quote:
Originally Posted by Drack View Post
Have you checked for shorts on the Mobo, maybe a shorted FET, dead Southbridge, have you bent the board? That worked for my old Biostar p4 mobo
I did not bent the mobo. But in the case there was more than enough corrosion. The bottom of the case was whole in corrosion spots, the mobo was dirty and this wasn't only dust - i'm sure of this. The price of the whole mobo is 5EUR second hand. If I short the green and black on the PSU, the computer starts, passes post and then suddenly turns off. Not worth the effort of fixing it, because of the dirt and corrosion.
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