Power Up As 480W atx power supply need help

[senz_90]

hello. everyone, i wanna asking for some help that i have facing now. first at all, my PSU dead before where it has no voltage on rails, just a 5VSB. the others no voltage exactly. after struggling i found that some components are defective and also i have changes it already. The PSU give me hope after changes the component and has a voltage again on each rails.. but i just feel there is still a problem insidely.

the problem is my ground cable (black) has a little voltage !! strange it showed that about 0.8-1.2V on my VOM. i guess there is short diode insidely, but after search around the PSU unit, i couldn't found it. all is checked with good condition. the picture below is my PSU, any advice and information really appreciated, please don't bother me to throw that cheapy PSU to the garbage and purchase a new one, because i wanna makes it to my bench power supply.. just a little experiment to get a cheapy bench power supply. for note, the marks with red sign in photo is the one that i have already change because failed.

i don't know is that really worth to fixed or not. i just wanna get experience to makes bench power supply from it.

[eccerr0r]

Re: Power Up As 480W atx power supply need help

Since your +5VSB is working the primary is probably OK, which means you can rule out the main bridge and the resistors likely nearby.

Of the PSUs I have been able to repair, so far these were what I found when +5VSB was working:
- main switching transistors blown
- main switch IC blown
- short somewhere on output circuitry

Still a lot of possibilities to look at... And yes the pictures you attached - I think I would have parted out and tossed that PSU

[senz_90]

Re: Power Up As 480W atx power supply need help

Since your +5VSB is working the primary is probably OK, which means you can rule out the main bridge and the resistors likely nearby.

Of the PSUs I have been able to repair, so far these were what I found when +5VSB was working:
- main switching transistors blown
- main switch IC blown
- short somewhere on output circuitry

Still a lot of possibilities to look at... And yes the pictures you attached - I think I would have parted out and tossed that PSU

lol. that's cheapy psu of course. main switch ic is tl431 ? im just a practician repairer. not really expert smps basic. hahaha. please show me where it is. i just think to changes that main switching transistor 13007 with 13009 for the best result. so an output maybe a short circuitry? any way to fix it? if you were me maybe that' s have parted out already

[Pentium4]

Re: Power Up As 480W atx power supply need help

Could be on the output, check the output rectifiers. Look very closely on both sides for discoloration of the PCB, maybe something got hot and burned out. But since that has 13007's, those are the most common failure in those old PSU's cause 13007's can't handle much, so check those first. You could put 13009's in there but I would seriously consider upgrading those heatsinks, that would help the efficiency a little too.

Nice job replacing the caps, but I would use at least 470uF on the input, 220uF caps could cause some issues

[ben7]

Re: Power Up As 480W atx power supply need help

main switch ic is tl431 ?

Nope, the main controller IC will be in a DIP style package, one common control IC is the TL494.

please show me where it is.

It should be on the low voltage side, it will be out in the open, not packed in-between the filter capacitors and inductors. It may be a TL494, UTC494, KA3500, SG35xx.... or it might one of those no-name '2001' or '2003' marked ones.

You can find the main switching transistor(s) on the heatsink next to those mains input filter capacitors. What are the part number(s)?

[senz_90]

Re: Power Up As 480W atx power supply need help

Could be on the output, check the output rectifiers. Look very closely on both sides for discoloration of the PCB, maybe something got hot and burned out. But since that has 13007's, those are the most common failure in those old PSU's cause 13007's can't handle much, so check those first. You could put 13009's in there but I would seriously consider upgrading those heatsinks, that would help the efficiency a little too.

Nice job replacing the caps, but I would use at least 470uF on the input, 220uF caps could cause some issues

i have checked three resistor very near my 2200uF caps for output filtering!! it gonna makes my changed caps bulged again within a few time.. it showed a little burn sign on the pcb but fine with the values. im gonna be stressed. checked and checked again with magnifier for short circuit but i couldn't find it.
the mains caps filtering have changed with 220uF because i am too lazy buying to the nearly store haha. so i just have it on my box and changes that caps looks cheapy. i have to change 13007, maybe give a good result. by the way. yesterday i just realize all rails have a voltage when i inserting my black probe VOM. it showed about 3 volt !! what is that anyway?

[senz_90]

Re: Power Up As 480W atx power supply need help

Nope, the main controller IC will be in a DIP style package, one common control IC is the TL494.



It should be on the low voltage side, it will be out in the open, not packed in-between the filter capacitors and inductors. It may be a TL494, UTC494, KA3500, SG35xx.... or it might one of those no-name '2001' or '2003' marked ones.

You can find the main switching transistor(s) on the heatsink next to those mains input filter capacitors. What are the part number(s)?

yeah the swithing transistor is 13007 and i want to changes it with 13009 and get a new heatsink if it available on my town..in my case that IC is KA7500B. it has a burned sign on the pcb nearly.. but just the transistor failed when i checked it. is there any chance maybe the IC failed?

[c_hegge]

Re: Power Up As 480W atx power supply need help

If the IC is burned, then it's almost definitely faulty.

[senz_90]

Re: Power Up As 480W atx power supply need help

If the IC is burned, then it's almost definitely faulty.

it is near has a burned sign, i definitely don't know if the IC burned or not, just near the IC on the PCB board. i'll changes it today maybe tomorrow with that switch transistor also.

[senz_90]

Re: Power Up As 480W atx power supply need help

heh.. i am fixing it now !! haha.. and the ground no voltage for now.. it looks normal and i try using big wattage resistor and the fan as dummy load and it function properly. this is the photos below.. the voltage i measure didn't disappointed i guess.

5V = 4,8V
3.3V = 3.5v
12V = 11.8V

so next i have to prepare for grinding and drill holes for my bench power supply.
i have changed diode nearly the ground cables, the transistor, and add an extra Y and X caps. also across mains with resistor high value. but i can't get a good heatsink around my town. many thanks for all of your helped..

[ben7]

Re: Power Up As 480W atx power supply need help

heh.. i am fixing it now !! haha.. and the ground no voltage for now.. it looks normal and i try using big wattage resistor and the fan as dummy load and it function properly. this is the photos below.. the voltage i measure didn't disappointed i guess.

5V = 4,8V
3.3V = 3.5v
12V = 11.8V

so next i have to prepare for grinding and drill holes for my bench power supply.
i have changed diode nearly the ground cables, the transistor, and add an extra Y and X caps. also across mains with resistor high value. but i can't get a good heatsink around my town. many thanks for all of your helped..

Good job! Surprised it worked first try, I guess nothing else was fried. Sometimes all hell breaks loose and it seems you just go in circles replacing parts, only to have others blow up.

[senz_90]

Re: Power Up As 480W atx power supply need help

Good job! Surprised it worked first try, I guess nothing else was fried. Sometimes all hell breaks loose and it seems you just go in circles replacing parts, only to have others blow up.

i have tested for about 20 minutes and got nothing to fried
before that i have test with series light bulb and i found that is no short anymore and trying to turn it on for about 20 minutes with dummy load. i have ever read that PSU can give me 13.8volt but i just think i wanna make it to have a multiple output. so i decide to make it likes the usual bench power supply. the issue maybe just i can't get a good heatsink for my diode and switch transistor around my town. very appreciate all of your help