Help with vmod gone wrong (8800GTS 640MB)

[sile__x]

Hello people! I would appreciate any kind of help or ideeas regarding my problem. I'm not proud of what I've managed to obtain this evening. Till 2 hours ago I had 2 8800gts 640MB in SLI running happy at stock volts.
Now, one of the cards is on the table with one of the small SMD missing. It is circled in yellow in the picture from SFED's volt modding thread for 8800gts G80's.



I managed to drop a small bubble of solder over that SMD and it unsoldered when I tried to clean it. With this error not beeing enough for today, the SMD stuck on the iron's tip and, ..... you've guessed right .... I've managed to lost it on the table/near it on the ground.
So, does anyone know :
1. the card can run without that SMD or I'll trash it if I'll power it on (I've seen that the 2 SMDs and the empty pad betwen them share a common end towards the Primarion chip) ?
2. i have the second card at hand, but I don't think that I can willingly unsolder that SMD even in 100 years .... to check it's value.
3. can I put a VR in the place of the missing SMD and what value (I measured the resistance of the solder pads, it can be seen in the picture)?

This is SFED's original thread about 8800gts G80 volt modding (I hope that he woudn't mind that I've used one of his pictures): http://www.xtremesystems.org/forums/...d.php?t=123046
Any kind of help would be appreciated. Thank you. I'll try to read the pdf of the primarion px3540 controller but I'm limited in this field .... http://208.109.51.75/PrimarionMain/D...s/PDB-3540.pdf

[lalPOOO]

Your Ohm measurements probably won't help you, as its quite possible that missing SMD is a capacitor. Don't power it up without it. If you can take a look around the area, it might be labeled as CXXX or RXXX. R meaning resistor, C meaning capacitor. If its a resistor you could remove an identical one and then measure off that and use the VR as you said, or just directly replace it with a resistor of the same value. If its a cap, or if you can't see anything labeling it as a resistor, its a cap and its going to be a little bit trickier. You can try emailing tech support for whichever company you bought it from and see if they have and are willing to share with you the capacitor specs. If they don't want to help you, find a dead 8800gts pcb or someone with one who doesn't mind helping you out and make the swap, or get them measure the cap for you (which requires equipment)
If you can't find another card, you will have to find someone/someplace nearby where you can take your other card and get the cap measured and replaced.
All in all, its not the end of the world, and those little mistakes happen to the best of us...
Good Luck! and Welcome to Xtremesystems (even though you've lurked for 2 years)

[ceemic]

Yes, its a cap. Probably around somewhere 100nF. I had that VGA, but not now. I can measure its capacitance, but I need to borrow that VGA from a friend and unsolder the same cap.

[sile__x]

MY DEEPEST THANKS to both of you.
I know this forum for a very long time(I was learning how to overclock athlons from here ), but I'm not a man of deep hardware modifications, so I resumed to small SMDs paint/pencil tricks till a year ago. I think that without good equipment one cannot do well in soldering area,especially in small SMDs, so I'll consider twice any crazy thought from now on.

I'll not power the card till I will find some way of measuring the SMD from the working one. I'm very found of both of the G80 boards (you can make me wired if you please ) But, I'm a little reluctant in chopping the second one. I have at work 2 good engineers, one of them automatician, who have good soldering tools, not my 15 dollar 25w generic iron, and I'll try to unsolder the good one with them, but even so, I'm very scared in doing this because of the very small size of the SMD.

Another thing that I saw today was that the empty solder pad trace between the 2 SMDs(in the picture - the empty solder pad on the right to the missing SMD) is cut, so that's the wired results from the measuring of the 3 SMD pads that are close to the Primarion chip.
Measuring the voltage read point to ground, but on 200 ohms set on DMM, I obtained 1,4 ohms on the working card and 1,6 ohms on the broken one (of course both cards were on the table, with 0 voltage supplied ). I was doing this because I was trying to see if the hole trace isn't broken because of the cut that I saw earlier. So, my question: it is possible that the lost SMD is a resistor ?.... A capacitor can make such a difference in resistance measuring ?

Thank you again for all the help and I'll speak tommory with my colleagues at work .

[PMM]

I think your OK looking at the tech doc for the IC
the capacitor forms part of the Vsense Circuit

It couple's between the Output and Ground and each side feeds
back to 2 sense inputs.

So I believe Voltage and current sense off the Output & Ground.

Essentially I think its just serving as a Filter capacitor feeding unwanted signals to Ground after the output.

[sile__x]

Ello ppl !

Back again .... The card is working now, thanx to you and my coworkers So, my advice after this experience: don't hesitate to ask for help from someone who is better than you in any field. If they want to help, the job will be done perfectly.
In 2 hours they made the unsoldered trace (by me) and, with the help of a 7 years old video card, they replaced the lost capacitor.
I'm very amazed by their patience and tools (I couldn't say it better than in first post... maybe in 100 years I could have done such of an artwork).
A picture is better than 1000 words ....



Thank you again ..... and I'm restraining from future soldered v-mods till I'll have better tools and some more patience.