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Bad Caps
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tedster
Posted 2020-01-24 6:37 PM (#1764)
Subject: Bad Caps



UMC U5S

Posts: 57
2525
Location: Scotland
My GF4 4400Ti has three domed caps. They've not burst yet and the card still works. However I've started getting a garbled display when it resumes from a blank screen.

The caps in question are 1000 uF 6.3v

I have some 1000uF 16v ones of a similar physical size, do you guys think they'll be ok?

I've pulled the card out of service as I really want to protect it.
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tedster
Posted 2020-01-25 12:13 AM (#1765 - in reply to #1764)
Subject: Re: Bad Caps



UMC U5S

Posts: 57
2525
Location: Scotland
Well, to answer my own question. It seems ok!

I could only find two caps, doh! However I traced them and they seem to be connected to each video out on the card. Maybe the 5v supply or something. Anyway, the best of the three appeared to go to the S-video, so I left that and changed the other two. They were the most domed and my theory is that they supply vga and dvi.

I've had the card resuming from a blank screen successfully, all evening. So fingers crossed!
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DXZeff
Posted 2020-01-25 5:46 AM (#1766 - in reply to #1765)
Subject: Re: Bad Caps



Pentium II

Posts: 490
100100100100252525
Location: Hull, UK
With capacitors you can generally go up in voltage, but never down. Personally I tend to only ever order 50V ones, because nothing in the things I repair should ever go that high and they'll last longer, you can even increase the capacity in some situations and get away with it - pretty certain I replaced 100µF 16V caps on my STB LightSpeed with 470µF 50v ones because they were all I had on hand and they're just filtering power, the little ceramic ones will be filtering all of the noise out, so using electrolytics larger than the original ones could arguably work better as they'll allow for a more stable supply of power. Ceramic ones or capacitors that are otherwise used in some resonant circuit (clock generators, probably) are more touchy though, the correct value must generally be used there as far as capacity goes, at least.

Edited by DXZeff 2020-01-25 5:48 AM
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tedster
Posted 2020-01-25 10:05 AM (#1767 - in reply to #1766)
Subject: Re: Bad Caps



UMC U5S

Posts: 57
2525
Location: Scotland
Thanks man! I always worry about making things worse with meddling. If it ain't broke, I'll "fix" it until it is, kind of thing!

This seems like one of my rare success stories. Leaving things until they go "pop" maybe takes out other parts a simple cap change can't cure.
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tedster
Posted 2020-01-25 11:36 AM (#1769 - in reply to #1767)
Subject: Re: Bad Caps



UMC U5S

Posts: 57
2525
Location: Scotland
I even get the card's full bios screen showing up now on a cold boot. I only ever got a brief flash of the screen before the MB bios shows, before.

The VGA memory does a count up! I don't remember seeing that on a video card before.

Awesome!


EDIT Found another cap and replaced the last of the domed ones.

Edited by tedster 2020-01-25 2:14 PM
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tedster
Posted 2020-01-26 3:03 PM (#1776 - in reply to #1769)
Subject: Re: Bad Caps



UMC U5S

Posts: 57
2525
Location: Scotland
One strange thing I noticed when replacing these caps.

The board was double drilled on the positive + leg. So fitting a physically larger cap was possible anyway. Maybe Leadtek cheaped out by using smaller caps for some reason? Maybe that's why they failed?
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tedster
Posted 2020-01-27 9:17 PM (#1777 - in reply to #1776)
Subject: Re: Bad Caps



UMC U5S

Posts: 57
2525
Location: Scotland
Ordered the correct ones but Panasonic low ESR ones this time. Instead of the generics that I used.

Because she's worth it!
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tedster
Posted 2020-01-30 9:39 PM (#1790 - in reply to #1777)
Subject: Re: Bad Caps



UMC U5S

Posts: 57
2525
Location: Scotland
Weird how they put the negative legs of the caps on the plain side, instead of the white.


I changed the three black ones in the picture. The rest look pretty good but who knows without a proper ESR tester?


Edited by tedster 2020-01-30 9:42 PM




(caps.jpg)



Attachments
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Attachments caps.jpg (258KB - 5 downloads)
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