Inno3D nVidia GTX 285 No Power (PC)

[api182]

Hi all! I know it's an old card but I managed to grab it cheap recently for my little brother who loves playing Minecraft and a bit of Fallout/Skyrim... and so this card will be ideal for the older games for now (teamed with his E7400 Core2Duo and 4GB DDR3 Ram...)

I got it knowingly that it was faulty with the hope that I could repair it...

I've managed to track the fault down to one of the 2x 6 Pin PCI-E Power Connectors, (SEE ATTACHED IMAGE) when I plug this in it doesn't allow my machine to even try to start and so it seems it's got that much of a fault on the power circuitry that it's cutting the PC's power circuitry out too... What I've tried so far is (with my little knowledge): -

I'm getting continuity across all the pins on the socket, I'm also getting continuity right through the 2 capacitors I've marked in the image also, I have de-soldered these capacitors to see if they were the issue but the continuity remains... I've done a lot of reading regarding the Mosfets and whilst the issue really does seem to point at that being the problem, I've checked all the Mosfets (Marked in the image) with just basic Continuity from my Digital Multimeter and they all give the same reading so it doesn't seem that one of them is broken..?

(How am I supposed to be testing them? I'm getting all the same figures from them???)

1.480 from Drain to Gate (- on the Drain and + on the Gate)
Then I get continuity from Drain to Source (Multimeter beeps)

Am I doing this wrong?

Any help will be most appreciated!

Thanks, Adam.

[Th3_uN1Qu3]

Re: Inno3D nVidia GTX 285 No Power (PC)

Continuity from drain to source is not good, it means one or more of the MOSFETs are shorted on that circuit. Start removing MOSFETs, beginning near the power connector, and re-test for shorts on both the board and the removed part. When you find a MOSFET that beeps drain to source even out of circuit, meabs it has burned and needs to be replaced. Repeat until the board no longer reads shorted.

Note: A low ohms value is not a short, so it's better to use the lowest ohms scale of your DMM and not the beeper. 3 ohms and above is not a short, 0.0 or 1.0 is. Of course, the removed MOSFETs should not read any resistance.

[api182]

Re: Inno3D nVidia GTX 285 No Power (PC)

Thank you so much for that, I'll get trying that now and report back!

[spleenharvester]

Re: Inno3D nVidia GTX 285 No Power (PC)

Yep bad MOSFET for sure, experienced it myself. Trace the PCI-E connector that prevents it booting back to the MOSFET area to narrow down which side you need to look at. Also it could just be the lighting but in your first picture the two MOSFETs to the left, third row down, appear to have no writing. If it's not the light causing that effect I would start by removing those two.

[api182]

Re: Inno3D nVidia GTX 285 No Power (PC)

That's true they don't have any writing on them, I saw that myself and thought about that, then because I was getting the same readings from all of them I thought that they might have just not been printed correctly at factory but yep, good idea, I'll start with them

[api182]

Re: Inno3D nVidia GTX 285 No Power (PC)

Guys, would just pulling the Source and Gate legs up from the board be enough to test or do I need to remove the drain also (the whole Mosfet?)

[Hoss]

Re: Inno3D nVidia GTX 285 No Power (PC)

I think you need to focus on the GPU. The 200 series is known for getting as hot as a furnace.

Many fixed their cards with a reflow, but if you can get it somewhere reballed for cheap that would be of course better.

[Th3_uN1Qu3]

Re: Inno3D nVidia GTX 285 No Power (PC)

That has nothing to do with his issue.

It's better to remove the MOSFETs whole. You'll break the legs if you wiggle them too much.

[momaka]

Re: Inno3D nVidia GTX 285 No Power (PC)

Since you have what appears to be a "short circuit" on the PCI-E power connector, that would indicate either a shorted ceramic capacitor between 12V and ground or shorted 12V line to GPU Vcc.

Ceramic capacitors are a little easier to remove, so let's start with those. You have C89, C90, C91, C92, C93, and C94 (those tan-colored rectangular boxes right where you circled the MOSFETs with yellow). Because you report that those capacitors on the bottom right of the picture appear shorted, my suggestion would be to start by removing C92, C93, and C94 first. Do so one by one and after removing each, test continuity on the 12V rail on the PCI-E power connector to ground. When the short is gone, you will have no continuity (no beeping). If that's not it, remove the other three ceramic capacitors - C89, C90, and C91.
....
Short circuit still remaining on 12V rail of PCI-E connector after trying the above? Okay, then that means those ceramic capacitors likely weren't the problem. The next step would be to start removing some MOSFETs.

Since the short is on the 12V rail of the PCI-E connector, that means the problem is then likely a shorted upper MOSFET in the buck regulator. Which one is the "upper MOSFET", you ask? Any of the MOSFETs labeled with "4821N". That would be, Q22, Q23, Q24, Q25, Q26, and Q27. So start removing them one by one and test continuity in PCI-E power connector after each. I suggest starting with Q25, Q26, and Q27, as those likely correspond with the short you see on those solid polymer capacitors you circled with red.

You will need a hot air station for this task, however.

Let us know what you find and how it goes.

It's better to remove the MOSFETs whole. You'll break the legs if you wiggle them too much.

Indeed.

[ameixoeiro]

Re: Inno3D nVidia GTX 285 No Power (PC)

Hi guys, I'm really curious to know if you managed to figured the fault out. I have a GTX 275, which is very similar to yours in PCB design, and mine has a different symptom. But anyways, I hope you repair yours!!

[SuperDuty]

Re: Inno3D nVidia GTX 285 No Power (PC)

I've repaired a handful of graphics cards with the same symptom, with continuity between +12V and ground on the PCI-E power connector, or that would prevent the system for starting (fans spinning for half a second and the power supply in "safe mode" ) : 9600GT, HD4850, 9300GE, 9500GT.
But it was only the larger type of MOSFET (TO-252 package) which are rather easy to remove, they the ones with the yellow highlight on your picture. The other smaller ones next to it, I don't know how to remove them, they looks like a BGA package or something.