Some old 400W Akasa psu bulged caps and more

[tdr]

This is some old power supply, it stopped working (didn't power on) several years ago. Bought new replacement. Recently I needed some psu for temporary built non important stuff. Bringed up this psu, replaced a few bulged caps. PSU is kinda working now, voltages reported from motherboard are o.k. (except some strange usb disconnect problems if more than few devices are plugged in), sometimes psu didn't turn on by pressing button but only manually connecting green and black wires.

But there is more. Looks like something was overheating there. On the board backside you can see burned mark too below R14A that is about right side in the middle of the board. Is this repairable? Too much components in a tiny space perhaps caused this?

[Per Hansson]

Re: Some old 400W Akasa psu bulged caps and more

R14A is the spot burned by the resistor, the black mark at the pad looks almost like poor contact.
Follow that trace and you will find another burned area, what's on the opposite side there?
Coming back to the other side of that resistor I think it's related to the 5VSB sircuit, seems to go down to the lone optocoupler at the boards edge.

On the left side of the board you have a capacitor or something which is not soldered on, a bit above R56.

[tdr]

Re: Some old 400W Akasa psu bulged caps and more

Above R56 is what I believe is my replacement capacitor and my bad soldering skills, it sure needs resoldering properly. I will check it out later and what's on the opposite side on the burned area.

Ok, looks like on the opposite side of the burnmark is diode below ZD1 mark. If I need resistor and diode replacement, what to look for? Are they common on spare psu parts or other board I can borrow from?

[momaka]

Re: Some old 400W Akasa psu bulged caps and more

I see two potential problems with this PSU: cheap Teapo capacitors and tan/brown glue that goes conductive over time.

Regarding the PC not turning all the time and USB devices becoming disconnected... that would most likely be related to bad 5VSB output filter caps. From the pictures you posted above, it appears that the 5VSB rail still has the original green Teapo (SC?) capacitors. I strongly suggest replacing those first, along with all other Teapo caps, before looking into the overheated resistors. Chances are, the Teapo caps are the reason why that happened. Removing as much of the tan conductive glue, especially from the primary side, is also very important. Once you get these two things fixed, then check if the overheated components are still in spec (they should be if the PSU still works after the cap replacement).

If I need resistor and diode replacement, what to look for? Are they common on spare psu parts or other board I can borrow from?

If you have other cheap PSUs (like Deer, Allied, L&C), those often have a good selection of through-hole components that you can use for repairing things.
So in short, yes.

[tdr]

Re: Some old 400W Akasa psu bulged caps and more

There are two big Teapo caps, larger one is 3300uf 10v, smaller one is 200uf 6.3v and there are two others hidden in the middle too far to easy reach and read labels. So I will replace these two ones with recommended caps. About the glue you mean that white-ish compound between components seen on the first pictures? If so, how to remove that hardened stuff?

[Per Hansson]

Re: Some old 400W Akasa psu bulged caps and more

Probably your 5vsb has gone high voltage but is being saved by that blackened zener diode on the primary side.
Replacing all electrolytic capacitors on the primary side except for the large bulk cap would be par for the course.
And at the same time all capacitors related to 5vsb on the secondary side.
But seeing how close the capacitors are to that big coil in there I'd replace them all in one go.
As I'm sure they must be really well baked by now.

[tdr]

Re: Some old 400W Akasa psu bulged caps and more

Never come to my mind that these big coils reaches high temp too, then maybe it is not good at all to use that psu at upcoming hot summer days when it reaches 25-28 degrees C in a room where pc is placed and instead just buy a new psu with cleaner design and more airflow inside. If only it was that simple...

[momaka]

Re: Some old 400W Akasa psu bulged caps and more

There are two big Teapo caps, larger one is 3300uf 10v, smaller one is 200uf 6.3v and there are two others hidden in the middle too far to easy reach and read labels. So I will replace these two ones with recommended caps.

Don't replace just one or two caps. Replace all of the output caps and be done with this so that you don't have to take it apart and open it again or wonder why the PSU is not working when more bad caps pop up.

That said, it is most important to get the 5VSB output filter caps replaced, as that will likely stop the overheated components on the primary from overheating further. You can see one of the 5VSB output filter caps (Teapo SC, 16V, 470 uF) on the bottom-left side of this picture:
https://www.badcaps.net/forum/attach...2&d=1528023173
There is another cap behind it, right next to that purple wire, which is likely the second output filter cap for the 5VSB (probably same voltage and capacitance). I recommend going with 6.3V or 10V cap rated for 1000 uF instead of 16V, 470 uF that is there originally.

About the glue you mean that white-ish compound between components seen on the first pictures? If so, how to remove that hardened stuff?

Well, I had a second look at your pictures, and it appears that I am wrong and your PSU only has regular white silicone glue, which is safe. So disregard my previous comments. It looks like when this component overheated, it discolored some of the white glue with sooth. But there doesn't appear to be any tan conductive glue anywhere else.

Never come to my mind that these big coils reaches high temp too, then maybe it is not good at all to use that psu at upcoming hot summer days when it reaches 25-28 degrees C in a room where pc is placed and instead just buy a new psu with cleaner design and more airflow inside.

Nah, the PSU will fine, even with those temperatures. My room regularly reaches 28-30C in the hotter summer days, and most of my old PSUs are fine with it.
While these big coils/toroids can run hot, they don't run that hot - at least not more than the insides of an LCD monitor power supply.

But if you use good quality Japanese caps, this won't matter too much, because they will withstand the temperature just fine.

[tdr]

Re: Some old 400W Akasa psu bulged caps and more

So it is ok to replace these 2 Teapo SC 16V 470uF with 6.3V or 10V 1000uF caps?

I have Panasonic branded 6.3V 820UF FJ caps. Are these decent for replacement?

And I do not have 3300uF 10V cap, so I will need to order that one. I do have Panasonic 3300 6.3V FJ caps at home but my guess is 6.3V will too low to use there (tallest cap in the last picture) so I better go safe and order 10V or 16V rated cap.

[Per Hansson]

Re: Some old 400W Akasa psu bulged caps and more

Better bring out a meter and check the voltage on the cap.
It would be unusual to use a 16v cap for 5VSB.

[tdr]

Re: Some old 400W Akasa psu bulged caps and more

I already replaced both caps, first was 470uF 16V and second one close to it was 1000uF 6.3V and I replaced both with 820uF 6.3V Panasonic FJ caps.

PSU running fine. Nothing blowed up at the moment. Volts are kinda ok (except bios showing 11.75V on 12V line but Speccy reporting 12.5V go figure but those reading were the same before replacement too). Will not run anything important on this setup anyway.

Just to be safe I think I will order replacement together with the 3300uF 10V cap.

[momaka]

Re: Some old 400W Akasa psu bulged caps and more

So it is ok to replace these 2 Teapo SC 16V 470uF with 6.3V or 10V 1000uF caps?

If they are connected to the 5VSB rail, yes. But as Per said, double-check with a meter. Though since the PSU is running, looks like they were.

I have Panasonic branded 6.3V 820UF FJ caps. Are these decent for replacement?

For 5VSB, yes. Low ESR, high ripple current caps are actually preferable for 5VSB, due to flyback topology. Though I would probably go with something like Panasonic FR and FM, Chemicon KZE and KYB, Rubycon ZLH, or Nichicon HE, as these have higher endurance rating (which is preferable, as PSU caps tend to run hot sometimes).

And I do not have 3300uF 10V cap, so I will need to order that one. I do have Panasonic 3300 6.3V FJ caps at home but my guess is 6.3V will too low to use there (tallest cap in the last picture) so I better go safe and order 10V or 16V rated cap.

Well, standard voltages inside ATX PSUs are 3.3V, 5V, and 12V. Both 6.3V and 10V caps can be used on the 3.3V and 5V rails, because they have higher voltage ratings that the voltage in the circuit (i.e. 3.3V and 5V). But for the 12V rail, neither 6.3V nor 10V caps can be used - here, you have to use 16V or 25V caps. So it's a pretty safe bet that you can use 6.3V caps in place of any 10V caps.

It would be unusual to use a 16v cap for 5VSB.

Quite common actually.
Old FSP/Sparke units do it all the time, as does Sirtec, and many modern HiPro/Chicony units. Reason why is because 16V caps are larger and thus have lower ESR and higher ripple current compared to 10V and 6.3V caps from the same brand and series. And since 5VSB typically uses flyback topology, it's better to use caps that can handle more ripple current.

PSU running fine. Nothing blowed up at the moment. Volts are kinda ok (except bios showing 11.75V on 12V line but Speccy reporting 12.5V go figure but those reading were the same before replacement too).

Meh. Onboard monitors are almost never accurate (save for CPU V_core voltage... though on older motherboards, I find that even this voltage is a bit off sometimes). So I always double-check my voltage with a multimeter.

Will not run anything important on this setup anyway.

Should be fine if you replaced *all* of the caps with quality ones. Otherwise, yes, don't put anything too valuable on it. Never know when crap caps are going to die.

Just to be safe I think I will order replacement together with the 3300uF 10V cap.

Get all the small caps replaced too. Really rip all electrolytic caps out except for the two big ones on the primary side - those are the only ones that are very unlikely to ever cause any issues.

[tdr]

Re: Some old 400W Akasa psu bulged caps and more

I just replaced 3300uF 10V with 3300uF 6.3V and PSU is still running fine.

That leaves one 330uF 16V to be replaced (small cap almost touching that big rail on the left side middle behind all wires so hardest to get to) this time I think I will not tempt my luck because I have only 820uF 6.3V left so I will look for proper replacement.

And the other one on the other side close to that big heatsink is rated 1uF 50V, should this need to be replaced too?

Also one small cap is on the child board screwed to that big heatsink, forgot to check the cap ratings there.

[Per Hansson]

Re: Some old 400W Akasa psu bulged caps and more

And the other one on the other side close to that big heatsink is rated 1uF 50V, should this need to be replaced too?

Also one small cap is on the child board screwed to that big heatsink, forgot to check the cap ratings there.

The small caps are always the most critical in a PSU.
When the wrong one fails usually in cheap power supplies you can say bye bye to your mainboard.

[tdr]

Re: Some old 400W Akasa psu bulged caps and more

Hard to find the right smaller cap from my local store, they all are the same 1uF 50V low impendance but with different operating currents and impendance. How do you tell the right cap to buy? (click on the link and then on caps picture to see full specs)

http://semicom.lv/SEARCH/?q=UPW1H010MDD
http://semicom.lv/SEARCH/?q=UPS1H010MDD
http://semicom.lv/SEARCH/?q=UVY1H010MDD
http://semicom.lv/SEARCH/?q=UTT1H010MDD
http://semicom.lv/SEARCH/?q=UPV1H010MFD

Maybe this is where I will stop and leave that smaller cap(s) alone. My psu is working anyway. Thanks for your time guys anyway.

[stj]

Re: Some old 400W Akasa psu bulged caps and more

i think PS series is for power supplies.
you have a surprisingly large range at that supplyer.

btw,if you see a guy climbing buildings and running across rooftops like spiderman with a gopro strapped to his head, give him a wave.
it's probably Desmond!!

[momaka]

Re: Some old 400W Akasa psu bulged caps and more

i think PS series is for power supplies.

Yup. Same goes for PW, PJ, PM, PV, PL, and PR (though be careful with old-stock PR - they like to leak from the bottom, especially if they are old). I'm not familiar with UTT, but it looks like a longer life series of the PW, so they can be used too.

Overall, it looks like your supplier offers a very good variety of low ESR caps, which is nice to see from a local shop (most carry no-name cheap junk caps from China/Taiwan).

As far as which to pick... for the small caps it really doesn't matter too much. PW, PS, PV, and UTT should all be better than what is currently in that old PSU.

That is, you can use these:
http://semicom.lv/SEARCH/?q=UPW1H010MDD
http://semicom.lv/SEARCH/?q=UPS1H010MDD
http://semicom.lv/SEARCH/?q=UPV1H010MFD
http://semicom.lv/SEARCH/?q=UTT1H010MDD

As for the VT series... i.e. these:
http://semicom.lv/SEARCH/?q=UVY1H010MDD
These are general purpose caps with 105C rating - great for repairing CRT TVs and monitors, along with audio stuff. In a pinch, you could use them in a PSU too, but it is not recommended because they probably won't last as long as the low impedance series and they also likely won't filter ripple and noise that well, due to the higher ESR.