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Old 08-11-2020, 04:59 PM   #1
sonicunderground
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Default Need Help Thermaltake Litepower 500W Problem

Hello everyone,
PSU: Thermaltake Litepower 500W Model: LT-500AL2NC
PCB: G08-CGPA462-PA00 Rev:A
I have this PSU installed in my PC for several years.
The problem is one day my PC cannot detect an external HDD so i think maybe the PSU caps already bad.
So i decided to open the case and found some of the secondary caps already bulging.
Then i recapping all the caps except the primary one (because i tested it with an esr meter and its still good) and i already tested all the new caps too before i soldered them.
After that the psu is good and my pc can detect my external HDD.
But 1-2 days later, when i using my pc suddenly i hear a clicking sound from the psu several times and then my PC turned off (about 5-10 min after the sound).
Then i removed the psu and tested it with psu tester and a light bulb (100W) in series with the AC mains.
Guess what, the light bulb shine brightly (something shorted!) and the psu fan spinning and i got all the voltage readings correct but only for a moment (about 1 min) after that all the voltage readings become 0 and only the 5vsb output remains.
So i open the psu again and start looking for the problem.
I tested the mains rectifier and all the diodes and it's all good.
I tested the filter safety caps OK, ZNR OK, Thermistor OK, Resistors in primary side OK.
I removed all the heatsink,tested the components and found the problem.
One of the 13N50 Mosfet in the middle heatsink is shorted and the PFR30L45CT diode in the secondary heatsink also shorted.
Then i decided to replace them but i cannot find the exact same parts in the local electronics store.
So i looked for similar parts and replaced all of the 13N50 with 15N50 and replaced PFR30L45CT with MBR30100PT.
After soldered all the parts and cleaning the PCB, i tested it again.
And now the AC mains light bulb is only flashed for 1 sec (charging the primary caps) and then turned off.
BUT, i still only got 5vsb readings on my psu tester.
So i decided to open the psu again (and again) looking for another problem.
I removed the KN2222A,KN2907A,TL431K,2SC1384L and found no problem.
I removed the PC817 opto and found one of them is bad, replaced all 3 of them with a new one.
But still no luck, all i got is only 5vsb output.
So, i wanna ask everyone here for help and maybe one of you have similar psu and know the problem.
I'm not an expert at electronics but i want to learn more about it.
Thanks in advance for your help.
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Old 08-11-2020, 07:31 PM   #2
RJARRRPCGP
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Default Re: Need Help Thermaltake Litepower 500W Problem

First photo: Too much flash glare!
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