Repairing Fortron Epsilon 600W

[Brainless]

Hi,
I want to restore one old PSU. I found the main reason to not working. It was small cap (100uF/25V) on the Vdc bus going to the PWM controller. I replaced the cap with 470uF/25V (don't have currently 100uF) and PSU now works, tested under load with old GPU (ATi HD5830) and Furmark software. The replaced cap doesn't have any external signs of malfunction, even with capacitance meter is value is OK. But with it Vdc bus is ~11V and adding a small value like 4.7uF put the bus right, where it should be ~15.5V.
What currently doesn't like is the spikes on 12V and 5V buses. Please see the attache files.
What can be the reason for such spikes? Main big filter cap? It is CapXon 470uF/420V and its value is also OK.

[ChaosLegionnaire]

Re: Repairing Fortron Epsilon 600W

i recommend u post photos of the inside of the psu and where that small cap is located inside the psu.

we need to see if its a group regulated design. from the power label u posted, it looks like it could be. if so, if u use a 12v hungry cpu and gpu, the 12v rail will sag and the 5v and 3.3v rail will go high. u need to load all 3 rails at the same time to keep them within spec.

were u able to scope/test the psu previously before that small cap failed? if it behaved the same way before the recap then its normal behaviour.

otherwise, it could also be that the filtering caps for the 5v and 12v rail are starting to go bad. fsp luvs using teapos and capxons in their psus so considering the age of the psu, it could be that the secondary side filter caps are bad too.

[Brainless]

Re: Repairing Fortron Epsilon 600W

Hi,
Thank you for the reply. The attached schematic is very similar to my PSU.
The replaced cap was C15, which in my case was 100uF/25V.
I found that for all caps, even they have the rated capacitance, their ESR is probably terrible due age. Just adding 100uF/400V to main filter cap, reduced the spikes more than twice. I ordered replacement for all caps.

[Brainless]

Re: Repairing Fortron Epsilon 600W

I replaced all caps, but the problem is still here - big spikes on all rails, with load and without. What is the usual voltage on the main filter cap? Currently is 400V.

[stj]

Re: Repairing Fortron Epsilon 600W

leave the 400v cap alone, it's not related to 200KHz spikes with what looks like some kind of resonant echo.

check the output diodes and snubber parts.
and what caps are you fitting??

[jarvis7]

Re: Repairing Fortron Epsilon 600W

Hello ,

I am guessing that these types of spikes are harmful/damaging for other PC hardware ?

Assuming PSU is using good quality Low ESR caps

is their any way of making sure that this does not happen without having oscilloscope or other expensive testers to test, simply with a basic multimeter ?

I mean as a complete newbie i get the impression from reading posts here that , simply using good Japanese Low ESR caps should be enough for a decent power supply to supply clean and safe output and be completely reliable.. else if something else in PSU is bad it would supply really bad voltages or won't work at all , something easy to discern..

this thread seems to suggest otherwise .. so if i buy a decently designed old used power supply and recap it with Japanese low ESR caps it still can be dangerous and unreliable and i cannot be fully sure that it is safe without having scope etc even though it is running PC fine ????

sorry if questions are too basic..

Thanks..

[Stefan Payne]

Re: Repairing Fortron Epsilon 600W

is their any way of making sure that this does not happen without having oscilloscope or other expensive testers to test, simply with a basic multimeter ?

No, you need to look at the voltage and for that you need an osciloscope.

[Per Hansson]

Re: Repairing Fortron Epsilon 600W

I mean as a complete newbie i get the impression from reading posts here that , simply using good Japanese Low ESR caps should be enough for a decent power supply to supply clean and safe output and be completely reliable.. else if something else in PSU is bad it would supply really bad voltages or won't work at all , something easy to discern..

I don't know what gave you that idea.
If anything without a scope it's much harder because you must match the capacitors to the original as close as possible.
And sometimes finding trustworthy datasheets for these crap brands can be impossible, case in point:
https://www.badcaps.net/forum/showth...013#post805013

[jarvis7]

Re: Repairing Fortron Epsilon 600W

Thank you very much Stefan and Per Hansson Sir