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Old 12-29-2010, 04:22 PM   #1
enduser
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Exclamation Dell Dimension 4700 - Bad United Chemi-Con

I was hired to troubleshoot a Dell Dimension 4700 PC that kept having random keyboard errors. I checked the BIOS log and noticed it had multiple errors with not only the keyboard but also with the memory, mouse, fan, etc.

I opened the cover to clean it figuring the heavy dust buildup was causing the CPU to overheat and generating these random errors. After blowing the dust out I found two United Chemi-Con caps leaking oil and with bulging tops.

The only two caps one each of the KZG, and KZJ series on the whole motherboard were bad. All other caps by United Chemi-Con are of the KZE series and are good.

New caps ordered will update when I install them.

2200uF 6.3vdc KZJ 105C, and 3300uF 6.3vdc KZG 105C

Last edited by enduser; 12-29-2010 at 04:25 PM..
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Old 12-30-2010, 02:22 AM   #2
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Default Re: Dell Dimension 4700 - Bad United Chemi-Con

Check the fan direction. Dell installed the case/cpu fan to blow IN. According to Dell, this is deliberate and correct. They even have a page dedicated to the issue warning you not to change it:
http://support.dell.com/support/topi...&isLegacy=true

However, in my experience, every 4700 I've worked on runs cooler with the fan blowing out in the traditional direction. Take from that what you will.
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Old 12-30-2010, 03:58 AM   #3
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Default Re: Dell Dimension 4700 - Bad United Chemi-Con

An inwards blowing fan was standard with old AT power supplies... till they figured out it gathers WAY too much dust this way. So i second the recommendation to flip it around.
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Old 12-30-2010, 04:09 AM   #4
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Default Re: Dell Dimension 4700 - Bad United Chemi-Con

It's one of those cases where DELL = Doesn't Ever Last Long
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Old 12-30-2010, 05:04 AM   #5
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Default Re: Dell Dimension 4700 - Bad United Chemi-Con

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Originally Posted by c_hegge View Post
it's one of those cases where dell = doesn't ever last long
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Old 12-30-2010, 07:31 AM   #6
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Default Re: Dell Dimension 4700 - Bad United Chemi-Con

Enduser, there is a transistor just to the left of the power supply socket by an inductor, Q5H1. Can you tell me the number of that? Took it out then lost it before I got the number. Thanks.
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Old 12-30-2010, 06:11 PM   #7
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Default Re: Dell Dimension 4700 - Bad United Chemi-Con

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Originally Posted by styxbound View Post
Enduser, there is a transistor just to the left of the power supply socket by an inductor, Q5H1. Can you tell me the number of that? Took it out then lost it before I got the number. Thanks.
It is made by ON semiconductor the numbers on it are shown as follows:

441 ON
T
11ON2
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Old 12-30-2010, 06:14 PM   #8
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Default Re: Dell Dimension 4700 - Bad United Chemi-Con

Mmm, isn't that 110N2 and Infineon? http://www.alldatasheet.com/view.jsp?Searchword=110N2
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Old 12-30-2010, 07:09 PM   #9
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Default Re: Dell Dimension 4700 - Bad United Chemi-Con

Hey thanks, guys. Thought I was going to have to wait until I run across another of these things.
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Old 01-14-2011, 07:32 PM   #10
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Default Re: Dell Dimension 4700 - Bad United Chemi-Con

Just like to update and confirm that replacing the mentioned caps fixed this motherboard. I replaced those caps with the Panasonic low-esr series
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Old 01-14-2011, 07:34 PM   #11
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Default Re: Dell Dimension 4700 - Bad United Chemi-Con

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Originally Posted by Th3_uN1Qu3 View Post
Mmm, isn't that 110N2 and Infineon? http://www.alldatasheet.com/view.jsp?Searchword=110N2
Thanks for the correction, I was not aware of this brand.
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Old 01-15-2011, 04:50 AM   #12
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Default Re: Dell Dimension 4700 - Bad United Chemi-Con

Infineon makes A LOT of motherboard mosfets. Some memory chips too.
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Old 01-16-2011, 11:39 AM   #13
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Question Re: Dell Dimension 4700 - Bad United Chemi-Con

Quote:
Originally Posted by enduser View Post
I was hired to troubleshoot a Dell Dimension 4700 PC that kept having random keyboard errors. I checked the BIOS log and noticed it had multiple errors with not only the keyboard but also with the memory, mouse, fan, etc.

I opened the cover to clean it figuring the heavy dust buildup was causing the CPU to overheat and generating these random errors. After blowing the dust out I found two United Chemi-Con caps leaking oil and with bulging tops.

The only two caps one each of the KZG, and KZJ series on the whole motherboard were bad. All other caps by United Chemi-Con are of the KZE series and are good.

New caps ordered will update when I install them.

2200uF 6.3vdc KZJ 105C, and 3300uF 6.3vdc KZG 105C

Hey enduser. I'm working on a friend's a Dell Dimension 4700 that has at least one bulging capacitor and the same symptoms you've described. I've removed all the motherboard retaining screws but the motherboard isn't releasing. It seem to be held near the CPU. Do you remember there being a hidden screw under the CPU heatsink? I didn't want to remove and re-seat the heatsink unless necessary.
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Old 01-16-2011, 12:58 PM   #14
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Default Re: Dell Dimension 4700 - Bad United Chemi-Con

Yes, almost all Dell Socket 775 CPU brackets screw to the case chassis. You're going to need to pull the heatsink. Under that there are 4 screws holding on the plastic retention bracket. Remove those and the motherboard should come out.
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Old 01-20-2011, 05:58 PM   #15
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Thumbs up Re: Dell Dimension 4700 - Bad United Chemi-Con

Replacing the 2200uF 6.3v KZJ located by the RAM slots solved the rebooting/stability problem with my friend's Dimension 4700. Works like a charm now!!
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