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MB recap with only one visually bad cap? Sharing experience..

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First post, by vutt

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I bought recently QDI Legend Superb 1 motherboard. Initially equipped it with Pentium 200Mhz MMX. Everything run well over few weeks. Installed DOS/Win 3.1 and Win98SE. No lockups/crashes. However visually only one power circuit Capacitor looked very slightly bulged rest are completely flat. See attached pic.
Then decided to buy AMD K2-450 CPU. Installed it run trough speedsys with default 100FSB@4.5x no issues. However when trying to run any game quake/doom PC restarted few seconds after game start. (Important: I used integrated SIS GPU)
Lowering multiplier to 4x everything seems to be working just fine - no crashes, used it for week or so this way.

So today I decided to pull out bulging 1000µF Cap and measure it ... ... measured around 200µF and ESR at 100kHz is 2.5 Ohm!! Ouch. Cap brand is DST. Unknown brand to me. However MB brand QDI/Legend I believe is today known as Lenovo.
After replacing it with some old more or less working Cap from my broken Athlon MB it started to run just fine with correct 4.5x multiplier.
Thought I share my experience that even only one slightly bulging one can make or break experience. I will probably order brand new set of caps. I really like this MB.

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Reply 1 of 4, by PD2JK

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Good job and thanks for sharing. Yes, one bad cap can give you headaches.

i386 16 ⇒ i486 DX4 100 ⇒ Pentium MMX 200 ⇒ Athlon Orion 700 | TB 1000 ⇒ AthlonXP 1700+ ⇒ Opteron 165 ⇒ Dual Opteron 856

Reply 2 of 4, by shevalier

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Most of the time in replacing capacitors is disassembling / assembling a PC.
When I get bored, I immediately change all the remaining ones. 😀

Aopen MX3S, PIII-S Tualatin 1133, Radeon 9800Pro@XT BIOS, Diamond monster sound MX300
JetWay K8T8AS, Athlon DH-E6 3000+, Radeon HD2600Pro AGP, Audigy 2 Value

Reply 3 of 4, by vutt

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Follow up: It turned out that all 12 1000µF caps were out of spec hovering around 500 - 300 µF capacity and ~2Ω ESR. No visible symptoms.
So I treated board with nice 9000h@105C rated Rubicons. Should be now good for next decade and them some...

Reply 4 of 4, by BitWrangler

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Some "uninteresting" boards that I've done zero dollar recaps on, I've taken all the major caps off one by one and tested with the component tester, within 10% they go back in, if not, junked, then I end up with a few empty spots I stick tested okay reclaimed caps from other junk into. So what I'm saying is even if not visibly bad, you can test them to be sure. It's not gonna put years and years of life on a board, but if you're just seeing if the board is useful before you drop $30 or so on major caps, you can get by with that method.

Unicorn herding operations are proceeding, but all the totes of hens teeth and barrels of rocking horse poop give them plenty of hiding spots.

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