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[RESOLVED] Finding voltage measuring points?

post #1 of 10
Thread Starter 
Noob here...redface.gif

I've been scouring the forums the past week or so trying to learn how to do a volt mod on my GPU (XFX 9800 GTX+) to increase the core voltage. Also, in general i'm just trying to eliminate any artifacts when overclocking the core clock and memory clock in Afterburner (stop me if I'm way off about what I should be doing now).

I've figured out how to measure the resistance using the pins on the voltage regulator and have done so.

What I would like to know is if there is a process I can apply to any GPU PCB to find out which points to use for measuring vcore, vmem, etc. (as well as figuring out where to solder)

Too lazy to pull card but i'm 95% sure this is my specific PCB...


also, I kind of randomly poked about while the pc was on getting readings here and there from various capacitors and pads in and around the white square, varying from 1.2v~2.48v so it really didn't help me figure out anything.

have another XFX 9800 GTX+ which appears to have reference PCB (NVIDIA logo)

measured stock voltage off cap C666, 1.19v, looked normal

measured resistance according to this picture from this guide and got a reading of 13 ohms

Is that normal? I was expecting something like at least 130 or 1300, unless i'm reading it wrong (DMM was set to 200ohm range so I'm pretty sure I did it correctly). FYI: been a while but I think i bought this card off ebay and it shipped from china (cheap knockoff issues?).
Edited by regularguy - 10/7/12 at 8:22pm
post #2 of 10
Holy crap, NEVER RANDOMLY POKE AROUND! Causing a short is no fun!

If I'm not mistaken you should be able to do volt mods by simply flashing a new bios to it (it's what I did with my 8800gt & GTX550ti). Doing hard volt mods was only relevant on cards that couldn't be flashed.

Look up some guides on NibiTOR, nvflash, and gpu-z.
post #3 of 10

Your doing good so far thumb.gif


 Guide looks good and complete - follow the pics GPUv



** any of the Caps around the outer left and upper edge will work .. they are all for GPUv.


The guide refers to a 1k trimmer or VR for the mod.. I think a 500 ohm would be plenty. Really what matters the most is you have enough resistance to still turn the VR back to stock settings once its in-line on the circuit [very important before you power up for the first time rolleyes.gif]

post #4 of 10
Thread Starter 

Also, am I boned if the pad that I was supposed to solder to (the one linked to the FB pin) comes off? Because it kind of just did when I was trying to apply hot glue to seal the joint but ended up ripping the whole thing off when I pulled away the gun >.<.

Is the capacitor right next to the solder point in this picture (http://www.xbitlabs.com/images/video/geforce9800gtx-voltmodding/gpu_mod400.png) also connected to the FB pin (was getting the same resistance readings off of it) and could I solder to that instead? (EDIT: appears the card still works, but is it unmoddable now in terms of core voltage?)
Edited by regularguy - 10/7/12 at 4:32pm
post #5 of 10

#1. ouch! doh.gif  ...cant say it hasnt happened to me before though redface.gif. There may still be hope.. we will get to that..

#2. If you have a "good mod point".. it has typically 2x very important characteristics: A- it has continuity to ground on one point  B- it is connected to 'FB'


 If you dont have enough trace left in the 'hole' to get a resistance reading from.. then leave it and use your other point... so long as it meets A/B from above. 

post #6 of 10
Thread Starter 
Well, took the card out and fired up the multimeter. I got a reading that stabilized at ~0.015 when testing between blue point and GND

Does that mean I've got continuity? Please excuse my ignorance, my DMM doesn't have a beeping continuity test and i'm not sure what to make of the reading.
Edited by regularguy - 10/7/12 at 5:36pm
post #7 of 10

Does the other side of the resistor marked in blue - measure with the correct resistance from FB?

post #8 of 10
Thread Starter 
It's pretty close

measured FB pin + ground (alligator clip on metal piece at the very end of the card) ~12.2 (remeasured and got ~12.9)
blue marked cap end + same ground ~12.9 ohms
post #9 of 10

should be good to go thumb.gif

post #10 of 10
Thread Starter 
Originally Posted by CL3P20 View Post

should be good to go thumb.gif

Wooh, yay!! Been smashing F5, thanks and I guess i'm ready to finally take the dive (again)...

Aside: bad joints are bad...
Edited by regularguy - 10/7/12 at 8:23pm
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