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Old 09-02-2007, 11:10 PM   #1
weirdlookinguy
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Default Dried-Out caps in a PSU?

Hello, I'm new to the forum so I'm not sure if this is in the right place, I apologize if it is not. I have a 5-year-old Gateway PC with a proprietary PSU which I believe has weak/dried out/dead caps. The system is used lightly and has ran fine without any issue for 5 years, but just a few days ago I took it apart to add a wireless PCI card. I unplugged power from the PSU, but the LED on the motherboard stayed on as it always does for a few seconds before power fully drains from the PSU. I don't know why, but just for the hell of it I pressed the power button to drain the power from the PSU. For a split second, the fans turned on and then everything died. Now that I think about it, this must have been bad for the PSU. Well anyway, installed the PCI card and plugged the computer back in and I got nothing, no power no green LED on the motherboard, lights out nobody's home. Uh-oh! I tried many power cables and outlets, but that was not the problem, however when putting in a known good spare PSU, the system booted right up so that meant the problem was with the PSU

I took the PSU apart, dusted it, looked for any cracked solder joints, nothing, so I put it back together and went to sleep. In the morning, I plugged it in again and it worked perfectly. I thought "WTF??" but the system was working fine so I left it like that. A few days later (yesterday) I accidentally unplugged the PSU from the wall. Upon plugging it back in, lights out nobody's home again just like last time. I let it sit overnight, but thsi time it didn't spring back to life the next morning. However, I tried it again a few hours later and it worked. It seems every time the PSU loses power, it must be left to sit for several hours before it will work again. Could this be dried out or dead caps? The PSU is 5 years old. I would just replace the PSU itself, but it is proprietary so any other PSU would have to be left hanging outside the case. So... dead caps?
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Old 09-03-2007, 01:18 AM   #2
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Default Re: Dried-Out caps in a PSU?

Quote:
Originally Posted by weirdlookinguy
Hello, I'm new to the forum so I'm not sure if this is in the right place, I apologize if it is not. I have a 5-year-old Gateway PC with a proprietary PSU which I believe has weak/dried out/dead caps. The system is used lightly and has ran fine without any issue for 5 years, but just a few days ago I took it apart to add a wireless PCI card. I unplugged power from the PSU, but the LED on the motherboard stayed on as it always does for a few seconds before power fully drains from the PSU. I don't know why, but just for the hell of it I pressed the power button to drain the power from the PSU. For a split second, the fans turned on and then everything died. Now that I think about it, this must have been bad for the PSU.
1) The caps would have drained either way, the acceleration of draining the caps is negligible as you wouldn't be able to do anything that matters before they had already drained.

2) No, it is not bad for the PSU. It really makes no difference, you just observed a bit of charge left in some caps that were draining down regardless of whether you pressed the button.

Quote:
Well anyway, installed the PCI card and plugged the computer back in and I got nothing, no power no green LED on the motherboard, lights out nobody's home. Uh-oh! I tried many power cables and outlets, but that was not the problem, however when putting in a known good spare PSU, the system booted right up so that meant the problem was with the PSU
I suspect it's most likely you just added that one more part that broke the camel's back. I mean your PSU was about at it's limits already and this was enough to do it in.

Quote:
I took the PSU apart, dusted it, looked for any cracked solder joints, nothing, so I put it back together and went to sleep. In the morning, I plugged it in again and it worked perfectly. I thought "WTF??" but the system was working fine so I left it like that. A few days later (yesterday) I accidentally unplugged the PSU from the wall. Upon plugging it back in, lights out nobody's home again just like last time. I let it sit overnight, but thsi time it didn't spring back to life the next morning. However, I tried it again a few hours later and it worked. It seems every time the PSU loses power, it must be left to sit for several hours before it will work again. Could this be dried out or dead caps? The PSU is 5 years old. I would just replace the PSU itself, but it is proprietary so any other PSU would have to be left hanging outside the case. So... dead caps?
There is no valid conclustion from what happens if you unplug the PSU from AC power. Leave it plugged in and assume nothing from what has happened to this point.

Only after you leave it as intended, an ATX system having continual AC power, resettting as necessary if you interfere with this, will any good conclusion be drawn.

It may be that the PSU does not have enough current for the system in it's new state, but until it is used in a regular manner this can't be determined. If it does seem the PSU is insufficient, I would suspect lack of capacity before bad caps, but if you just felt like replacing caps anyway, replace those in the 5VSB subcircuit.
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Old 09-03-2007, 01:52 AM   #3
weirdlookinguy
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Default Re: Dried-Out caps in a PSU?

That PCI card had already been in there for months, I had taken it out to try it in another machine and was putting it back in when the PSU incident happened. Also, after the PSU came back to life, it worked great with the PCI card. Also, I don't think the motherboard is getting any trickle voltage from the PSU (no green LED on the motherboard). The PSU has always made a weird whining since day one and when it is dead, it doesn't make this noise.
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Old 09-03-2007, 03:38 AM   #4
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Default Re: Dried-Out caps in a PSU?

The Quality of the PSU aside and yeah if you have to use a supply buy a good one, but in you case the case style is an issue
(I think they may fall in the crapola company of psu's but not sure)

humm well I had an issue with a supply a few years back were if you turn it off but left it connected to mains it would not start...in order to get this to happen I had to unplug it from the mains for awhile.
I eventually tracked it back to a resistor...I think from memory it was a dry joint on it.


now not the guru on smpsu's and dont know how the beastec are put together function wise

I suspected with mine it must have been a fault with the startup circuit in relation to the constantly on +5V standby.
(I think a cap was suppose to be discharged by that resistor to enable the startup function to happen when the power switch was pressed)

I am thinking that you have an intermittent fault with your psu of this nature.

Since the Stanby 5+ section is constantly powered up while plugged in the caps have been powered for five years, also carefully check that area of the psu cause it sounds to me like this type of fault.

The short answer is get another supply to make sure it the supply thats the issue

If the supply is that old and still working and you haven't got much choice I would do a full recap on it

If this is the supply that you posted the voltages on, then TC's answer about the stdby being a tad High might be a clue as to the fact it has a fault.

As I said I don't know how its put together circuit wise to give you a more informed answer.

I suspect the psu, but the only quick why to know is to change it for a known working good one.

Also If you haven't already...look at the caps on the MB and check if there crap or good ones.

cheap supplies and there rating you can take with a big dose of salt mostly,
so if this is the box you going to use a new graphics card on and if its one that pulls juice I would definitively look for a better quality/power psu and if it was me recap the MB

Anyway thats my thoughts on it and yeah agree with 9's reply above, except I think it is the psu ....more precisely the startup circuit that is the issue..you must remember too he hasn't read your second post in this thread yet either.

HTH cheers and Welcome
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Old 09-03-2007, 04:20 AM   #5
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Default Re: Dried-Out caps in a PSU?

I would advise a recap of the 5v stand by section too or replace the PSU, as the problem your described is very typical and common.

As long as you let it plugged in, the caps are staying warm. If caps has gone fubar, their spec do improve when heated up.
If you let it cool down, they need some time to get warmer and then the psu starts up.

The problem with those nasty 5v sb circuits is, that if the caps have lost the capacitance, the regulation circuit can`t regulate the voltage anymore.
Thus it is not uncommon that this elevated voltage destroys some important chips at the main board.
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Old 01-20-2008, 12:46 AM   #6
weirdlookinguy
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Default Re: Dried-Out caps in a PSU?

Hey everyone, revisited this thread and realized I never told you guys what happened. I figured I should in case someone has the same problem; this thread might help them. First of all, this was not the Bestec PSU I posted about and it's not the one I was going to be putting a graphics card into. It's the supply on my brother's computer.

It turns out it was a bad 25v cap, swapped it out and the PSU has been running well ever since, the problem with turning it on is gone. Dunno what the 25V cap did. This PSU is weird. There were a few Rubycons in there, and a Nichicon, but everything else was just random, unknown caps. The motherboard is an intel board loaded with Rubycons, so no need to recap that.

I might be ordering some caps from DigiKey for something else soon, but since caps are so cheap online I might recap this PSU. Hell, I'll probably recap the Bestec in my main system while I'm at it. I've also got some crappy Evercons in my graphics card that have to go. Hmmm....
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Old 02-04-2008, 09:12 AM   #7
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Default Re: Dried-Out caps in a PSU?

Thanks for the feedback and the fix you found, it may help someone so its good you posted a conclusion
caps like these in these positions are more toward the GP variety they don't need to be low esr super caps, but a quality cap of similar specs wouldn't go astray either.
(if its a potential piece of junk thats been used.)
make note of its position and brand (type) for future reference.

even crap caps you will get a reasonable run out of them but they will fail sooner rather then later, I guess all manufactures have to worry about is if it will live a little pass the warranty period then its not their problem.

Thanks Cheers
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Old 03-10-2008, 06:54 PM   #8
GEOcros
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Default Re: Dried-Out caps in a PSU?

Quote:
Originally Posted by weirdlookinguy
...but since caps are so cheap online I might recap this PSU. Hell, I'll probably recap the Bestec in my main system while I'm at it. I've also got some crappy Evercons in my graphics card that have to go. Hmmm....
I still don't know how much they cost. Others are saying $1-2 each-WTF !!!
I'm loocking for 6.3v 820uf 105c CAP and also 1000uf, 1500uf's. Where did you find them?
Even i went to RUBYCON website but i'm not a PRO and can't find them.
Maybe you can help me?
Thanks.
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Old 03-11-2008, 03:27 AM   #9
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Default Re: Dried-Out caps in a PSU?

If you are in US send PM to Topcat he can supply. Recommended.

If Outside the US PM Big Pope for your needs.
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