8800gt risistor missing after crasy mod

[turbopropello]

some dude "helped" me mod a pov8800gt resulting in just a mess

but now i have thaken that card to a car chip store where i worked before
and the "solder" guy there is going to try to fix that board...
( he modded a second pov for me user the vmoc whit Vr ( 1000 ohm )
but i havent started turning up the volts yeat ( looks like there will be a lot of turning allso before volt goes up when i understand its @ 500ohm and less the voltage starts to rise... re that i am going to rise until 1,29 idle desktop using swifttech water block on cpu and sinks on ram..

but can someone themm me the value ( 15 ohm) of the resistor
marked red on this pic? so we can try to fix the other card?

[largon]

Too bad the measument can't be done without first desoldering the part. :(

Good thing is, one doesn't need to! :)
Just measure the one on it's left and calculate (http://www.1728.com/resistrs.htm) the needed value for the missing one so that the combined resistance is ~15Ω.
Please post what the resistor immediately to the left of the resistor marked in red measures.

[winbond]

did u figure out what ohm resistor goes there cause id like to know too,

also can anyone tell me what this red point connects to? ? cause i broke it off and this resistor is supposed to be connected to it. thanks

[trez0r]

The red dot is unused. You can do without it as long as the resistor below it is still connected to the one to the left from it.

[largon]

winbond,
Follow the light green trace to find out where the spot you're talking about is connected. First it goes down, then left, up, then it ends in the 6th leg (counting from right) of the IC in the top edge of the pic

[winbond]

thanks and thanks for the replies, i can see where it goes the way you described it, but i meant going the other direction, (i guess it's not going anywhere the other way, like trez0r said)..

...largon, can you explain a little more how to figure out the resistor value, i read what you said but i don't get it, i looked at the calculator you pointed to but it says 3+9+18 ohms = 2 ohms , huh? :shrug:

[turbopropello]

Too bad the measument can't be done without first desoldering the part. :(

Good thing is, one doesn't need to! :)
Just measure the one on it's left and calculate (http://www.1728.com/resistrs.htm) the needed value for the missing one so that the combined resistance is ~15Ω.
Please post what the resistor immediately to the left of the resistor marked in red measures.

the one on the left messuers 12 ohm

[winbond]

i don't think the 12ohm is the resistance of that resistor, i think it's the resistance of the entire circuit it's connected to, right/wrong?

[jason4207]

Unless he removed it from the board it is the entire circuit.

[turbopropello]

he did not remove it from the borad... should he?

[winbond]

lolz, no, once u start removing more stuff u'll never get this card back together
,

we're somehow supposed to calculate the resistance of that resistor by measuring the circuit resistance, which is 12ohm + the missing resistor and that is supposed to give us ~15ohm circuit, however i don't know the way they calculate it.

[mike047]

60 ohm???

[winbond]

how did you figure out the 60 ohm?

[mike047]

how did you figure out the 60 ohm?

I don't think that's correct. I went and got my calculator and am trying again....I am old and slow:D

edit;
60 is correct.

I can't correctly explain how I did it but I used the link given. Just substitute 60 for R and do the math.
Sorry I don't have a better explanation:(

That is assuming all 4 resistors are in the circuit.

EDIT AGAIN;
I still NOT sure that is correct...it's late and I'm tired and stupid:D

[STEvil]

You're going to have to find where that dot goes to, it probably carries a signal to/from somewhere.

[winbond]

i thought we had some electronic geniuses here, but no one can figure out the value of that resistor? :confused:

[largon]

mike047,
What "4 resistors" are you talking about? There's only 2 in the vGPU sense network.
And btw, 60Ω makes no sense. we're somehow supposed to calculate the resistance of that resistor by measuring the circuit resistance, which is 12ohm + the missing resistor and that is supposed to give us ~15ohm circuit, however i don't know the way they calculate it.Now, this here is an mathematical inequality.
If there's a 12Ω resistor in the circuit and we have another one parallel to it then it is absolutely, literally impossible to reach 15Ω - or anything above 12Ω - by installing a resistor of any value. I reckon we're dealing with a DMM missreading/inaccuracy here. Resistance at the low tens is difficult to reliably measure with a cheap DMM.

[mike047]

mike047,
What "4 resistors" are you talking about? There's only 2 in the vGPU sense network.
And btw, 60Ω makes no sense. Now, this here is an mathematical inequality.
If there's a 12Ω resistor in the circuit and we have another one parallel to it then it is absolutely, literally impossible to reach 15Ω - or anything above 12Ω - by installing a resistor of any value. I reckon we're dealing with a DMM missreading/inaccuracy here. Resistance at the low tens is difficult to reliably measure with a cheap DMM.



POST #14;
EDIT AGAIN;
I still NOT sure that is correct...it's late and I'm tired and stupid

You are correct in your statement and that was what I was seeing also, BUT being old, tired and "stoopid" I faded out:ROTF:

edit;
Knowing nothing about the card in question, I "assumed" the 4 adjacent components were in the circuit:rolleyes: ...I know better than to assume anything ...sorry:p:

[winbond]

i'm gonna pull my card out and remeasure the resistance, turbopropello said it's 12ohm and i measured 12 ohms myself but that was measured with the vgpu mod on and lowered resistance on the VR, so i'll unsolder the mod and measure it again

[largon]

winbond,
You'll be measuring the whole circuit not a single resistor...

[winbond]

ok, i see, well i'm not gonna unsolder that resistor because it will probably brake and i'll be totally screwed, i'm gonna have to wait for someone else to figure it out, thanks

[oohms]

huh its easy.. measure the resistance on your broken card between the 2 points the resistors were, then measure across the same resistor on a card with it in place (and no vmod attatched)

Then we can work it out

[winbond]

i only have one video card, even though it's messed up it still works , because i blindly added a resistor of about the same size ,(not value), but the card doesn't overclock well, anyways, i measured what i could with the vgpu mod and the fake resistor taken off,

- points 1 and 2 are gone so i can't use them
- missing resistor between point 2 and 3
- i can still use point 5 instead of 2 because they are directly connected anyway, right?
- point 3 to ground = 1.1 ohm
- point 3 to point 5 (2) = 13.1 ohm
- point 4 to ground = 4.2 ohm
- point 4 to point 5 = 10.1 ohm
- point 5 to ground = 14.1 ohm

[G H Z]

Is the trace termination below point 3 still intact? If so I'd uncover it and go between there and the side of the resistor above point 5/to the left of point 1

[winbond]

yes, the pad under point 3 is fine, thanks for pointing it out , i'll probably use that resistor as the missing point 2, only someone still needs to figure out the value of it :yepp:

[G H Z]

Why not use a VR so you can adjust it? Once it's soldered in place you can match the resistance on a working card without needing to know the value.

[winbond]

hmm, that's a good idea too, i might do that later, for now i just soldered in a 0.5 ohm resistor and im gonna live it in for now, thanks

edit
well, .5 ohm is not good, needs to be a higher value, the card shots down with little over 1.2v

[winbond]

edit, still experimenting

.5ohm resistor, card shots down @ ~1.22v
20ohms resistor card shots down @ ~1.36v

after the card shots down, i get extremely high voltage to the core, like 3 or 4v (i have the 2 resistors removed for OCP mod)

what do you guys think, should i go with like 500ohm resistor?

[Dawgdoc]

Winbond, good luck fixing your card.

I dont want to hijack your thread, I just want to say that those closeup pics are AWESOME for being so dang close.

What brand/make digital camera do you have?

[turbopropello]

pic is cred of http://www.xtremesystems.org/forums/member.php?u=13027 ( Largon )

i found something i think might have messed up another card.. we used a 1000 ohm vr.. but its 64w? could this mess everything up??

i am posting the ohm of the missing resistor whitin 24 hours.. ( xmas.. i know someone who gets a orginal card...)

[largon]

That pic (http://img148.imageshack.us/img148/1354/img0830bbbbbq5.jpg) was shot by dinos22 (http://www.xtremesystems.org/forums/showpost.php?p=2523498&postcount=10) with a Canon PowerShot G9.

[winbond]

i'll be glad to finally find out the actual value of the resistor that goes there,
i have tried 0.5, 20, 500, 700, 1k and 4.5k ohm , the higher the resistance the higher working voltage i could get from the volt mod, but card is unstable after an hour or so of gaming anyways, and i'm only running it 750/1900 core/shader @ 1.3v,

[Diverge]

after the card shots down, i get extremely high voltage to the core, like 3 or 4v

shouldn't that be something to be really concerned about? 3-4v... that would probably damage your chip, if not blow it up lol

[mieller]

i have also lost a resistor for the vcore on a 7800gt reference design. can i just put a variable resistor where the missing resistor was?

[turbopropello]

got my hands on a new unmodded one
messured the first one( marked red to 13,6 ohm the one to the right og it to 10 ohm...


some dude "helped" me mod a pov8800gt resulting in just a mess

but now i have thaken that card to a car chip store where i worked before
and the "solder" guy there is going to try to fix that board...
( he modded a second pov for me user the vmoc whit Vr ( 1000 ohm )
but i havent started turning up the volts yeat ( looks like there will be a lot of turning allso before volt goes up when i understand its @ 500ohm and less the voltage starts to rise... re that i am going to rise until 1,29 idle desktop using swifttech water block on cpu and sinks on ram..

but can someone themm me the value ( 15 ohm) of the resistor
marked red on this pic? so we can try to fix the other card?

[winbond]

thanks for posting it, i looked around many broken electronics and no where i could find a tiny black resistors of this value, it's always either .5 or smaller or 20 or higher,

[turbopropello]

maybe find some old boards and start messuring

[largon]

I resoldered the vGPU mod on my 8800GT and ran into a little problem.
I somehow managed to destroy the same resistor as the one on turbopropello's card. After poking some dead motherboards with the solder iron hoping to find useable surface mount resistors I was left no other choice but to desolder the second resistor too and place a single linear 14.6Ω resistor in their place.

Works fine...
But looks absolutely horrid.got my hands on a new unmodded one
messured the first one( marked red to 13,6 ohm the one to the right og it to 10 ohm...One simply cannot measure the resistance of two parallel resistors without first braking the circuit. There is no way whatsoever to measure individual resistors if they are connected in parallel.