Bad bad capacitors

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Postby jimmy-j » Tue May 13, 2008 2:03 pm

Bad caps in other computer equipment:-
Belkin Wireless Cable/DSL Gateway Router Model # F5D6231-4 ver 1000

Gloria 1500uF 6.3V
Gloria 1000uF 6.3V
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Post subject: Bad bad capacitors

Postby GeorgeCCarter » Tue May 13, 2008 9:24 pm

Add to that the ASUS K8N8X-LA motherboard (a motherboard made for HP machines) specifically HP Pavallion A640N, also referred to as the Diablo UL6E.
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Postby jimmy-j » Thu May 15, 2008 1:32 pm

jimmy-j wrote:Bad caps in other computer equipment:-
Belkin Wireless Cable/DSL Gateway Router Model # F5D6231-4 ver 1000

Gloria 1500uF 6.3V
Gloria 1000uF 6.3V


Well I replaced those capasitors and got the thing working, I only had a 10v 1000uF but it seems to be working OK, I am on the net with this unit at the moment, I was a bit confused when I removed the first cap and the Neg stripe was on the shaded side(not the white side) so I fitted the new one in the same orientation, however when I came to do the other cap the neg stripe was on the white half, Is it possible this is where the fault came from in the first place?.
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Postby Karlsweldt » Fri May 16, 2008 1:10 pm

If properly manufactued, the mobo will have small icons where the capacitors are to go, to indicate the (+) or (-) terminals. Easier to see than tiny characters.
Per the design "flavor" of manufacturers, the labels may be different. But always look for those positive and negative symbols for orientation! If you found a unit that was installed backwards, likely it would have blown apart within a few minutes or seconds of getting power!
The safe rule concerning voltage is to stay at least 20% above circuit designs.
With audio output coupling capacitors, it is best to go with a 2x higher rating than circuit voltage.

It is safe and acceptable to replace a capacitor with one of a higher voltage rating.. but never lower! But always use the same capacitance value, unless additional filtering is needed on power circuits. The value of the capacitor is otherwise critical with timing circuits and DC isolation.
With AC capacitors, they are just two standard DC capacitors.. in series, but with two like terminals mated.. such as positive to positive. If voltage flows in reverse to the polarity, then a simulated dead short would be present. Hence the pairing of two identical caps that present "no" polarity.
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Postby jimmy-j » Sun May 18, 2008 4:23 pm

Well, the capasitor that I thought was in backwards blew again and I replaced it with one of the same size but the other way round, (The way I thought it should have been done in the first place) Now it is running again and been fine for the last few hours, Going to leve it pluged in through the night to check it out but I feel confident it will run witrhout any further trouble.
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Postby Mr T » Sat Nov 15, 2008 11:45 pm

Now add the ASUS A8N-SLi deluxe....
I have been programming on computers since the ZX81.
I am an apprentice trained Electronics Engineer with qualifications to back it up.
I have been repairing computers since 1996.
Yet to some people I still know nothing...
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Postby evasive » Sun Nov 16, 2008 3:53 am

Is it me or is the entire socket754/socket939 line of Asus boards showing up here? That would be NO fun at all...
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Postby evasive » Sat Jan 17, 2009 6:56 am

asrock p4vm890, the one near the northbridge. I see a strip of green/gold ones that I spotted on other bad boards too... I wonder when they will go... :(
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Postby Karlsweldt » Wed Jan 28, 2009 2:11 pm

Not sure if the problem is common, but my second system has developed the 'bad caps' affliction! It is an ECS 848P-A, Socket 478. Worked perfectly for a few years, then the past few days it would lock up with no reason. Only a hard reboot got it working again. I reset the device cards and memory, and happened to spot three domed caps just behind the CPU!
It will be down until I replace the caps. No sense in running it and causing any permanent damage. The caps were 1500 mfd, 16 volt.. branded "Ost" with a '+' on the top. Will be monitoring my other system, with a similar Chaintech mobo.
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Postby evasive » Thu Jan 29, 2009 2:11 am

branded "Ost" with a '+' on the top.


bingo, these are used on my Shuttle AV49N and the failed Asrock P4VM890 so we now have an official "bad brand" to avoid completely. Wow.
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