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Old 10-23-2018, 06:44 AM   #1
hed190
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Default Dell Optiplex 745 SFF Bad Caps

Hey Guys,

Been searching through the forum for threads about optiplex 745 sff, and i found a few that help a lil but my problem is still a problem...

Already replace the blown 2200uF 6.3V capacitors but they keep swolling and licking, it could be other component causing this?

I touched the north bridge (the one with the heat sink) i guess, and it is so hot that almost cant touch it.

Opened the power dupply and didn't see nothing wrong.

My cpu is a core 2 duo 1.8GHz.

I have a few computers of these in need to be repaired, so can you guys help?

Regards,
Hed190
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Old 10-23-2018, 10:27 AM   #2
Uranium-235
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Default Re: Dell Optiplex 745 SFF Bad Caps

what brand/series are you replacing them with?
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Old 10-23-2018, 04:06 PM   #3
Curious.George
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Default Re: Dell Optiplex 745 SFF Bad Caps

Quote:
Originally Posted by hed190 View Post
Hey Guys,

Been searching through the forum for threads about optiplex 745 sff, and i found a few that help a lil but my problem is still a problem...

Already replace the blown 2200uF 6.3V capacitors but they keep swolling and licking, it could be other component causing this?

I touched the north bridge (the one with the heat sink) i guess, and it is so hot that almost cant touch it.

Opened the power dupply and didn't see nothing wrong.
Funny thing about electrons -- they're awful hard to SEE!

Do your troubleshooting skills END with your eyes? Have you checked the voltages on the power supply outputs? And, around the board?
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Old 10-23-2018, 08:21 PM   #4
dmill89
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Default Re: Dell Optiplex 745 SFF Bad Caps

Quote:
Originally Posted by hed190 View Post
Already replace the blown 2200uF 6.3V capacitors but they keep swolling and licking, it could be other component causing this?
More than likely the caps went bad on their own, the OptiPlex 745s were at the tail-end of the bad Nichicon HM/HN fiasco so the caps may have been defective to begin with (and Dell also used Chemi-Con KZG/KZJ which were known for issues as well) and even if they weren't defective caps, SFF systems are famous for running hot and "cooking" that caps so after 14 years failure wouldn't be unexpected even for "good" caps.

I'd definitely check all the PSUs and consider recapping/replacing them as well if they have second-tier caps (Ltec, Lelon, Elite, CapXon, etc.) even if there aren't any obvious failures.

Quote:
Originally Posted by Uranium-235 View Post
what brand/series are you replacing them with?
x2? remember motherboard caps need to be replaced with low-esr/ultra low-esr caps with specs equivalent to the originals, just "any old caps" won't do.

Last edited by dmill89; 10-23-2018 at 08:23 PM..
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Old 11-01-2018, 05:57 PM   #5
momaka
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Default Re: Dell Optiplex 745 SFF Bad Caps

Quote:
Originally Posted by hed190 View Post
Already replace the blown 2200uF 6.3V capacitors but they keep swolling and licking, it could be other component causing this?
Did this happen right away after changing the caps or over some period of time.
If it happened right away, it is possible you placed the new caps backwards. Remember, electrolytic caps are *polarized*, meaning there is a negative and a positive terminal. Get it wrong and you get instantly bulging/leaking caps as soon as you power up the machine.

Now if the failure happened over a longer period of time, there are several reasons this could have happened. One could bet that you used inappropriately-rated caps (not low ESR or not low enough compared to originals). It could also have happened if you happened to buy counterfeit caps. OR, it may not be your fault at all, and the caps could have failed due to excessive heat, which is typical for most SFF PCs, as dmill89 suggested.

Another good point that dmill89 mentioned is to replace any crap caps in the PSU, regardless if they look bad or not. Indeed Ltec, CapXon, OST, and Teapo are all known to go bad without visual signs sometimes.
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