cooler master rs-750 load problem

[Guilty_2121]

Hi everyone,
my power supply shuts off under load, starts with out problem, the i tried to play game or benchmark, pc shuts off. I check the caps they looks good and looks like no weak solder. what shout i suspect?
model: cooler master rs-750-amaa-b1

[stj]

Re: cooler master rs-750 load problem

caps still - they need to be removed and metered with an esr meter

[momaka]

Re: cooler master rs-750 load problem

Can you post some pictures here of the internals of the power supply? That way we can see what you have.

Also, did you try your PC with another PSU and confirm the system can stay turned On under heavy load? Just asking to make sure we are not troubleshooting an issue that may not exist (i.e. possibly having the system be faulty and not the PSU.)

[Guilty_2121]

Re: cooler master rs-750 load problem

Can you post some pictures here of the internals of the power supply? That way we can see what you have.

Also, did you try your PC with another PSU and confirm the system can stay turned On under heavy load? Just asking to make sure we are not troubleshooting an issue that may not exist (i.e. possibly having the system be faulty and not the PSU.)

Yes, i take my friends 600w and try for 3 days and everything is good on PC.
back side is looks ok. no weak solder.

[momaka]

Re: cooler master rs-750 load problem

Yes, i take my friends 600w and try for 3 days and everything is good on PC.

Ok, good to know. So it likely is the PSU, then.

Based on the pictures you provided, I see a lot of CapXon capacitors. Generally, CapXon does show signs when it goes bad (bulging, leaking, and etc.) But because it's a very crappy brand, it really is hard to know if any of those caps are actually good or not without pulling them out of the PSU and measuring them with an ESR meter. If you have an ESR meter (one of those cheap GM328 multi-function testers will do - they cost about $15) or if you have a friend / know a repair shop that has one, then it would be best to remove each cap and test it. Capacitance should be within +/-20% of what is printed on each cap. And ESR should be less than 0.1 Ohms for most of the caps (the really small 5x11 caps may show up to 2-3 Ohms, which isn't considered terrible.)

Again, because none of the caps look bad, my suggestion would be to start with the small ones seen in this picture, as they are most prone to drying out and not showing visible signs of failure when they do go bad:
https://www.badcaps.net/forum/attach...5&d=1618137991

If they test OK, remove and test the two big caps shown here:
https://www.badcaps.net/forum/attach...3&d=1618137991

And if those test OK, then check the rest of the secondary-side electrolytic caps, which can be seen here:
https://www.badcaps.net/forum/attach...7&d=1618137991

Also, post a clear-focused picture of the under-side of the PSU, if possible. I would like to see if anyone of us can spot anything on there that perhaps may have gotten overlooked.

[Guilty_2121]

Re: cooler master rs-750 load problem

Ok, good to know. So it likely is the PSU, then.

Based on the pictures you provided, I see a lot of CapXon capacitors. Generally, CapXon does show signs when it goes bad (bulging, leaking, and etc.) But because it's a very crappy brand, it really is hard to know if any of those caps are actually good or not without pulling them out of the PSU and measuring them with an ESR meter. If you have an ESR meter (one of those cheap GM328 multi-function testers will do - they cost about $15) or if you have a friend / know a repair shop that has one, then it would be best to remove each cap and test it. Capacitance should be within +/-20% of what is printed on each cap. And ESR should be less than 0.1 Ohms for most of the caps (the really small 5x11 caps may show up to 2-3 Ohms, which isn't considered terrible.)

Again, because none of the caps look bad, my suggestion would be to start with the small ones seen in this picture, as they are most prone to drying out and not showing visible signs of failure when they do go bad:
https://www.badcaps.net/forum/attach...5&d=1618137991

If they test OK, remove and test the two big caps shown here:
https://www.badcaps.net/forum/attach...3&d=1618137991

And if those test OK, then check the rest of the secondary-side electrolytic caps, which can be seen here:
https://www.badcaps.net/forum/attach...7&d=1618137991

Also, post a clear-focused picture of the under-side of the PSU, if possible. I would like to see if anyone of us can spot anything on there that perhaps may have gotten overlooked.

At first thank you so much master. And here is the pictures you want.
I like to fix my thing and i can spend several hours on try. But this is a little hard for me but i will try my best and tell the what happen

[momaka]

Re: cooler master rs-750 load problem

Well, just to say here that I'm battling the same (or very very similar issue) with a Rosewill Valens 600 PSU. The PSU itself is quite different from this one, but it's doing something similar: it will turn On and run fine without a load (or with a very very light load, like an HDD or two) with all voltages in spec. But the moment I try to run any motherboard with it or heavier load, it turns Off. So if I find anything that might be related, I'll report back too. I haven't had a chance to check the caps yet, but I suspect that the issue might be either a small "startup/run" cap somewhere gone bad or perhaps the APFC / main input filter cap gone/going bad.

[goodpsusearch]

Re: cooler master rs-750 load problem

I would bet the main APFC cap has lost most of its capacitance

[Guilty_2121]

Re: cooler master rs-750 load problem

I would bet the main APFC cap has lost most of its capacitance

I don't know which one you are pointing but i change the all caps in the middle area(nearly 6) and problem fixed. And I change the output area too. Only 2 big ones left(2 caps with 400V).

[stj]

Re: cooler master rs-750 load problem

he's talking about the mains side caps