One man’s garbage = an [H]’s 7800GTX SLI

Servant of Shodan

[H]ard|Gawd
Joined
Dec 28, 2002
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This is an expansion of a “Post your favorite card of all time” post I made.

I occasionally buy stuff off of eBay that is listed as “untested” or “As Is”, with hopes of scoring a great find for cheap. It has worked out very well in the past.

So one day, I bought a 7800GTX that was listed as non-working, just to see if I could fix it. When it arrived, I saw under the small black heatsink, that one of 9 mosfets was obviously burned out and damaged. Of course, the card would not boot.

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So I got to wondering if I could fix this by finding an equivalent part and soldering it back on. I carefully removed the damaged one, and it was not at all pretty.

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I quickly knew that I was not going to be able to resolder anything… Well, I thought for a while, “Why would there be so many mosfets? I wonder if there is any built-in redundancy? Like the space shuttle, right?” So I put the heatsink back on, pop it in the PCIe slot, push the power button, expecting nothing to happen (but also ready to put out any electrical fire that starts)… and the computer POSTs. Without any screen corruption.

So, I’m thinking, “OK, this is cool, but how long can it last before it reboots, or Windows is all artifact-ed…” But everything worked just fine! After several hours of looping 3DMark, I figure it’s good to go. So I’m happy, considering that I paid about $35 dollars for this card that cost $600 not too long ago.

And then I think, “Please sir, may I have another?” I go back onto eBay and score another. Again, for about $35! It arrives, same mosfet burn-out, I do the same procedure, it works perfectly! And so now I have SLI 7800GTX.

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I have just purchased a 3rd 7800GTX, it has the exact same issue, and this one is going into a computer I’m building for my dad.

I have no idea why this works! Logic tells me that is should NOT work. But nothing ventured, nothing gained! The moral of the story is, fellow [H]’ers, never give up!
 
lol nice find, and grats on the new system :)

Have you run any games / benchmarks to see if they have any slowdowns or problems?
 
Hahaha. Awesome

Get a fan to blow over that area though please... The load is being split across only a few MOSFET's now, instead of all of them :)
 
Very nice dude. curiosity + tweaking pays off. But all three of them had the same exact issue? Whats up with that?
 
Get a fan to blow over that area though please... The load is being split across only a few MOSFET's now, instead of all of them :)

Yes indeed! That little black heatsink gets VERY hot, and one of the first things I did was to put an extra 80mm fan blowing right in their direction.

Have you run any games / benchmarks to see if they have any slowdowns or problems?

Yup, I ran 3DMark2005, and it was the smoothest I'd ever seen in my life! I also played Prey for a couple of hours without issue. So they run just fine.
 
thats [H]ard!

so really, whats up with the mosfets? is this known..what do they do, why does it work like this....

just curious on others inputs
 
thats [H]ard!

so really, whats up with the mosfets? is this known..what do they do, why does it work like this....

just curious on others inputs

they are voltage regulators
 
I am not certain, but have reason to believe that these all came from Gateway machines. Reason is, the company selling them on eBay had about 30 of the exact same cards for sale, and on the item description, he said, "For detailed specifications go here," and he posted a link to Gateway's Customer Service/technical specs.

I did not check the BIOS (good idea by the way) for volt mods, but I did give everything a good look-over through Rivatuner, and they look as stock as could be.

I really think these are just cards that were put in Gateway machines with poor ventilation, maybe poor Power Supply Units, and maybe a bad batch of mosfets.

Thanks for the story on GPUReview.com, mentok1982! I wish it was The Force that guided my hand! :D
 
I am not certain, but have reason to believe that these all came from Gateway machines. Reason is, the company selling them on eBay had about 30 of the exact same cards for sale, and on the item description, he said, "For detailed specifications go here," and he posted a link to Gateway's Customer Service/technical specs.

I did not check the BIOS (good idea by the way) for volt mods, but I did give everything a good look-over through Rivatuner, and they look as stock as could be.

I really think these are just cards that were put in Gateway machines with poor ventilation, maybe poor Power Supply Units, and maybe a bad batch of mosfets.

Thanks for the story on GPUReview.com, mentok1982! I wish it was The Force that guided my hand! :D

I noticed they looked very off brand, almost Nvidia reference. Great stuff tho. 70 bucks for those two cards is sweet.
 
That doesn't look to bad. Shouldn't have been hard to replace that mosfet. Mind you if it works without it so be it.
 
Thanks for the story on GPUReview.com, mentok1982! I wish it was The Force that guided my hand! :D

It's not very often that a story like yours comes around that has to do with video cards. It is a
very specific site so I can't just post anything that I find.
 
That's awesome!

However I think your game may be over now. :-p

Everyone is gonna now try to buy defective 7800s!
 
haha cool story & nice deal, but the true odds of this happening are low.. i mean if i did the same thing as you and bought AS IS or NOT WORKING vidcards, I'd have blown cash away since most of the time the gpu or ram is fried beyond all repair
 
haha cool story & nice deal, but the true odds of this happening are low.. i mean if i did the same thing as you and bought AS IS or NOT WORKING vidcards, I'd have blown cash away since most of the time the gpu or ram is fried beyond all repair

True. It is indeed a gamble. But this worked out for another eBay-er too. He bought two 7800GTX cards, and I told him about the success I had. He tried it on one of his, and got it running too! His other, however, was not to be revived. No question, it is risky.
 
I guess all that hacking in System Shock 2 paid off ;)

Amazing find, I wonder if anyone sells that on the Mexican e-bay... I should find out....
 
absolutely Awesome m8... two 7800GTX in SLI for $70:eek:. as for MOSFETs i think replacing them should not be a problem. But since its working, no point doing that now. might try it myself....
 
Definately a Gamble I would not recommend it to people you just got lucky. Alot of the time the NEW hardware I get does not even work!

But hell, I lost my 8800GTX money in vegas anyways.
 
WOAH, nice find man! A true bargin, 2 7800GTX for $70 WOW lol. Anyways its a HUGE risk if you buy one. I doubt all have the same problem, but still I am going to try this, and see what I get.
 
I tried to bid on some but I think because of your post they all went for like $50. it's a bit too much of a gamble for $100 when you can use thats towards buying a faster 8800 GTS.
 
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