Swollen caps - old computer. Why so many bad caps? Computer not used in years.

Thread Starter

Tonyr1084

Joined Sep 24, 2015
5,039
Last time this computer was powered up it had no problems. Today I attempted to fire it up and got no video at all. Having removed the MB, there are 12 caps (electrolytic) with swollen tops. 5 of them to the point of a small bit of leakage at the tops. I'm wondering why these caps went bad. Were they bad last time I used the computer and I got lucky it worked? Or have they gone bad from sitting all this time with no power?

All but two are odd values - 820µF @ 6.3V (9 count). The two are 1500µF @ 6.3V. I happen to have some 1500µF's @ 10V (Low ESR) but don't have any 820µF's. So I'll be ordering some. The 10V cap is larger than the 6.3V caps, so I'll probably be ordering some of those as well.

Do caps go bad just sitting around? My thought is they shouldn't.

I'm guessing I probably should go ahead and change all the caps because others, though not showing any signs of trouble may be at the precipice.
 

jpanhalt

Joined Jan 18, 2008
10,219
In my limited experience, the PS for a monitor alone (like the one I am using right now) has at least 6 caps. Replace them and be happy...if it works.
 

Thread Starter

Tonyr1084

Joined Sep 24, 2015
5,039
What era was the computer?
2003 is when I purchased it.

The ONLY reasons why I want to continue using it is it operates on Windows XP and operates my Hantek Computer scope. I have the Hantek disk but it won't load to my Windows 10 computer. Have tried several times and have reached out to Hantek but no response.
 

dl324

Joined Mar 30, 2015
11,485
Do caps go bad just sitting around? My thought is they shouldn't.
Electrolytic caps can go bad when not being used, but at a slower rate than when they're powered. Aging can cause reduced capacitance, increased leakage, and increased ESR. They'll try to reform when power is applied, but sometimes they don't survive. Some use a low wattage bulb in series with power to limit current while they reform; some use a Variac and increase voltage slowly.
The ONLY reasons why I want to continue using it is it operates on Windows XP and operates my Hantek Computer scope.
Computers capable of running XP should be inexpensive now. I have a stack of them left over from when I was refurbishing and giving to needy families. Now that XP is unsupported, that stopped because giving someone who isn't computer literate a Linux computer is asking for trouble all around.
 

ScottWang

Joined Aug 23, 2012
6,933
The first issue is that the quality of capacitor liquid, and the second issue is that the rated voltage, for a 5V power, 6.3V rated voltage is not good enough for the long term use, so you better change it to 10V, for a 12V power, 16V rated voltage is not good enough for the long term use, so you better change it to 25V unless you could find a 20V.

I have had repaired many old computers main board(mother board) and PSU, I replaced much more new capacitors for PCB with over old rated voltage, and they all worked fine, unless there is bad quality of capacitor liquid inside the capacitor.

One day in many years ago, I bought the new capacitors at the local EE store, when I went home to check the them, and I found out that some of them already bluged, so I went back to the local store to changed to the new capacitors, and also asked him what reason caused the capacitors bluged.
 

jeffkrol

Joined Dec 8, 2015
14
Personally.. As noted bad Chinese corporate espionage.. second, think they realized they could use the bad cap design for planned obsolescence.
 

MrAl

Joined Jun 17, 2014
7,800
Last time this computer was powered up it had no problems. Today I attempted to fire it up and got no video at all. Having removed the MB, there are 12 caps (electrolytic) with swollen tops. 5 of them to the point of a small bit of leakage at the tops. I'm wondering why these caps went bad. Were they bad last time I used the computer and I got lucky it worked? Or have they gone bad from sitting all this time with no power?

All but two are odd values - 820µF @ 6.3V (9 count). The two are 1500µF @ 6.3V. I happen to have some 1500µF's @ 10V (Low ESR) but don't have any 820µF's. So I'll be ordering some. The 10V cap is larger than the 6.3V caps, so I'll probably be ordering some of those as well.

Do caps go bad just sitting around? My thought is they shouldn't.

I'm guessing I probably should go ahead and change all the caps because others, though not showing any signs of trouble may be at the precipice.
Hi,

Electrolytic caps can leak and still work, so the product may work for some time before it stops working completely. You can tell because usually you see several caps that have leaked when you take something apart and the chances are slim that they all started leaking at the exact same time.

My experience has been that the error detection circuits (like over voltage or under voltage cutouts) do not detect anything right away, and then when they do start to detect an error they dont detect it every time you turn the product on, they instead let it run for a while first and then shut it down after either a long time or a short time depending on how bad they got. Once my computer power supply would start shutting down maybe once a day, then twice a day, then more times per day, then eventually it would shut down after only maybe an hour. Once it gets annoying enough you tend to want to do something about it, so i took off the cover to the power supply and found the leaking caps. After replacing them it worked fine again.
The same thing happened with an LCD TV set i had. That one got harder and harder to turn on because it would shut right down as soon as you tried to turn it on, but then sometimes it would stay on. Taking the back cover off, there were electrolytics that were leaking. It was the caps that were in the low voltage DC section of the power supply, same with the computer. The TV acted bad in a progressive way also, first it would turn on ok, then it would take two times to turn it on, then three times, then it got really hard to turn on so i never knew if one day it would not turn on at all so that is when i decided to tackle the problem. After replacing the caps, worked fine again.
 

Ramussons

Joined May 3, 2013
871
2003 is when I purchased it.

The ONLY reasons why I want to continue using it is it operates on Windows XP and operates my Hantek Computer scope. I have the Hantek disk but it won't load to my Windows 10 computer. Have tried several times and have reached out to Hantek but no response.
Just a diversion. Is it nor possible to run the XP in a Virtual box to operate the Hantek?
 

MrSoftware

Joined Oct 29, 2013
1,906
2003 is when I purchased it.

The ONLY reasons why I want to continue using it is it operates on Windows XP and operates my Hantek Computer scope. I have the Hantek disk but it won't load to my Windows 10 computer. Have tried several times and have reached out to Hantek but no response.
2003 was smack dead in the middle of the capacitor plague (see the link in my previous post). I've seen sooo many things from that era fail due to capacitors going bad. Electrolytic capacitors are chemical and have a finite shelf and service life anyway, but during that era the failures were just off the charts. Replace them now with good capacitors and it will probably last longer than you want to use it. Look into the soldering iron tweezer tool, I don't know what the real name is, but it might be helpful in getting those things off and on again. I don't know if this specific set is any good, but this is the general idea. I would try putting a bunch of solder and flux on either side, then use something like these to get the solder under both sides to flow at the same time:
https://www.amazon.com/VPABES-Portable-Tweezers-Soldering-Repairing/dp/B07QYMW9NS/ref=sr_1_9?dchild=1&keywords=soldering+iron+tweezers&qid=1597845100&sr=8-9
 

bob2

Joined Jun 15, 2019
194
Last time this computer was powered up it had no problems. Today I attempted to fire it up and got no video at all. Having removed the MB, there are 12 caps (electrolytic) with swollen tops. 5 of them to the point of a small bit of leakage at the tops. I'm wondering why these caps went bad. Were they bad last time I used the computer and I got lucky it worked? Or have they gone bad from sitting all this time with no power?
Many motherboard capacitor problems arise from failures and poor operation of the power supply. It is necessary to check all supply voltages and an oscilloscope to check the level of ripple of the main output voltages. Otherwise, after a while, the same will happen with new capacitors.
A good in-circuit ESR meter is very useful here, with which you can quickly check all capacitors and identify deviations in their parameters.
 

bob2

Joined Jun 15, 2019
194
The ATX12V Power Supply Design Guide requires that the peak-to-peak (distance from minimum to maximum) residual ripple of the output voltages of power supplies at maximum load does not exceed 50 mV for +5 V and +3.3 V rails and 120 mV for + 12V rails.
 

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Thread Starter

Tonyr1084

Joined Sep 24, 2015
5,039
The first issue is that the quality of capacitor liquid, and the second issue is that the rated voltage, for a 5V power, 6.3V rated voltage is not good enough for the long term use, so you better change it to 10V, for a 12V power, 16V rated voltage is not good enough for the long term use, so you better change it to 25V unless you could find a 20V.
Changing from 6.3V to 10V means a different spacing on the through hole caps. Higher voltage caps will have to sit above the board.
Personally.. As noted bad Chinese corporate espionage.. second, think they realized they could use the bad cap design for planned obsolescence.
#1 - OK. #2 - OK. #3 - Compaq!
Electrolytic caps can leak and still work, so the product may work for some time before it stops working completely. You can tell because usually you see several caps that have leaked when you take something apart and the chances are slim that they all started leaking at the exact same time.
As you may have noticed from the picture (if clear enough) some caps are swollen, others clearly have leaked. I've pulled a few off so far, but have been busy with other matters. Will return to removing the old caps later today.
Look into the soldering iron tweezer tool
One issue I've had with removal of these caps is that the power plane is pretty thick, and it takes a lot of time and heat saturation before you can work the leads out of the solder.
Many motherboard capacitor problems arise from failures and poor operation of the power supply.
Replaced the ATX supply about 6 or 7 years ago. Computer has sat for around 3 to 5.

Someone mentioned Hantek not working in an XP environment. I believe it did. Can't swear it does - but I think it did.
 

ScottWang

Joined Aug 23, 2012
6,933
Changing from 6.3V to 10V means a different spacing on the through hole caps. Higher voltage caps will have to sit above the board.
If you can't do that for the PCB then you should find the caps made in Japan (or Japanese company) or other countries that you can trust, and then you can buy the same rated voltage.
 
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