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Alright, so I'm thinking about doing the pencil mod on my 7800GT. I'll trace the resistor with 2B or 6B artist lead depending on how much resistance each takes away. However, I don't know how to measure the resistance or the resulting voltage... Do I measure resistance (Ohms) when the GPU is hooked to no power out of the case? And if so, where do I take the measurement - the vmem register or the resistor that I'm tracing? And how do I measure the resulting voltage increase? Should the card be in the case and running for this? And will this be from the vmem register?<br />
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Here'e the reverse side of the PCB:<br />
<img src="http://img247.imageshack.us/img247/6586/7800gtvmemsz4.png" border="0" alt="" onload="NcodeImageResizer.createOn(this);" /><br />
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The vmem register is the taped over hole and the resistor is the red circled one, with my proposed trace made in red right next to it...<br />
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Thanks for any help you guys.
 

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Discussion Starter #3
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<div>Originally Posted by <strong>born2killU</strong></div>
<div style="font-style:italic;">do you have a multimeter<br><br>
if so just measure it in volts and see which one adds the most</div>
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Yes I do have an analog multimeter, but where would I read the voltage from on the PCB? The taped over hole shown in the picture, or at the resistor? And do I measure voltage while the card is in the PC and running? Or out of the pc with no power running to it?<br><br>
I'd also like to know how to measure resistance in ohms as that would be helpful as well <img alt="" class="inlineimg" src="/images/smilies/smile.gif" style="border:0px solid;" title="Smile"><br><br>
Thanks though born.
 

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depends on what voltage u want...
 

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Discussion Starter #5
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<div>Originally Posted by <strong>Ace_001</strong></div>
<div style="font-style:italic;">depends on what voltage u want...</div>
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Well according to a guy on XS forums, the stock voltage is ~2.08v and stock resistance is 620ohms, so with a layer of graphite, he reduced the ohms to 600 and this made the voltage 2.14v. So I would be shooting for at least 2.14v, but I would like to know how to measure the ohms so while the card is out of the pc, I can check what the voltage will be like before popping it in and frying my card :-\\
 

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Measure the resistance between the location of the orange wire and the upper left black wire. This should be done with the card out of the case without any form of power applied. Wait, I'm looking at it wrong...and the pot in the picture is throwing me for a loop :-\\<br><br>
The "card out of case without power" still stands. As for the resistance measurement for this pencil mod, I don't think I'm on the same page as you.
 

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Discussion Starter #7
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<div>Originally Posted by <strong>Xavier1421</strong></div>
<div style="font-style:italic;"><b>Measure the resistance between the location of the orange wire and the upper left black wire</b>. This should be done with the card out of the case without any form of power applied.<br><br>
As far as the other stuff, I don't pretend to know anything about it, so I'm not gonna throw out any dangerous suggestions. <img alt="" class="inlineimg" src="/images/smilies/smile.gif" style="border:0px solid;" title="Smile"></div>
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Oh, so I would put the black side of the multimeter on the black ground in the pic and the red side on the resistor where the orange wire is in the pic?<br><br>
Iiiiiii gotcha... any idea what I should set my multimeter to? I know it has that confusing dial of settings lol :-/<br><br><b>The pot is just a VR...</b>
 

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A VR is just a pot <img alt="" class="inlineimg" src="/images/smilies/smile.gif" style="border:0px solid;" title="Smile"> haha<br><br>
This is a one or the other situation. Either pencil mod it, or solder in the 10k VR. What kind of multimeter is it?<br><br>
Pencil modding in this case is like trying to jump the resistor, or bypass it, with graphite. Measuring resistance across the resistor before and after the mod by using the "upside-down horseshoe" setting on the meter.
 

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Discussion Starter #9
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<div>Originally Posted by <strong>Xavier1421</strong></div>
<div style="font-style:italic;">A VR is just a pot <img alt="" class="inlineimg" src="/images/smilies/smile.gif" style="border:0px solid;" title="Smile"> haha<br><br>
This is a one or the other situation. Either pencil mod it, or solder in the 10k VR. What kind of multimeter is it?</div>
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Ehh, I really don't want to mess around with solder and my nice 7800GT, I'd rather just do the wimpier hard mod lol...<br><br>
And I'm not sure what kind of multimeter it is, I know that it's got an analog "speedo" style guage on it... I'll come back tomorro and post what kind it is and inquire as to how to set it I guess, it's down in the basement and I don't feel like gettin it...<br><br>
Thanks for the help though everyone, and Xavier, if you figure out how I'm supposed to measure the resistance and/or voltage, please tell, I'll get it tomorrow.<br><br>
Thanks again <img alt="" class="inlineimg" src="/images/smilies/smile.gif" style="border:0px solid;" title="Smile">
 

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Discussion Starter #10
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Originally Posted by <strong>Xavier1421</strong>

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<div style="font-style:italic">A VR is just a pot <img src="/images/smilies/smile.gif" border="0" alt="" title="Smile" class="inlineimg" /> haha<br />
<br />
This is a one or the other situation. Either pencil mod it, or solder in the 10k VR. What kind of multimeter is it?<br />
<br />
Pencil modding in this case is like trying to jump the resistor, or bypass it, with graphite. <b>Measuring resistance across the resistor before and after the mod by using the "upside-down horseshoe" setting on the meter</b>.</div>

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</div>Does it matter which contact, red or black, is on which side of the resistor or does it just read it the same either way? And I check resistance with the GPU out of the case with no power correct?
 

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Discussion Starter #11
Do you measure voltage with the vid card in and the computer on and running?<br />
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Just checkin cuz I need to test the voltage on my GPU and mem.
 

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Originally Posted by <strong>kidwolf909</strong>

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<div style="font-style:italic">Does it matter which contact, red or black, is on which side of the resistor or does it just read it the same either way? And I check resistance with the GPU out of the case with no power correct?</div>

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</div>Resistance is not directional, so it does not matter. Also these are passive devices no need to power on the GPU - resistance is a function of the conducting material only. The Ohmeter itself will apply a current source to solve the resistance taking into account its own impedance.
 

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Originally Posted by <strong>kidwolf909</strong>

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<div style="font-style:italic">Do you measure voltage with the vid card in and the computer on and running?<br />
<br />
Just checkin cuz I need to test the voltage on my GPU and mem.</div>

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The video card must be connected to its power source in order to have any potential on the video card PCB. To measure the voltage you will need to measure relative to a VSS (ground) source (preferably on the PCB). For comparo, always use the same ground source.
 

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Voltage = while the card is on...(direction matters)<br />
<br />
Resistance = while the card is out of the case.(direction does not matter. Touch the ENDS of the resistor..shade the TOP..from one end to the other)<br />
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Please, please, please!!! Someone blew up his card by measuring resistance while it was on...lol. Good luck.<br />
<br />
(if you hook up the leads backwards...you'll get a - reading(or 0, depending on the multimeter you use). So you'll know. Just flip it around.
 

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Originally Posted by <strong>Sideburns</strong>

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<div style="font-style:italic">Voltage = while the card is on...(direction matters)<br />
<br />
Resistance = while the card is out of the case.(direction does not matter. Touch the ENDS of the resistor..shade the TOP..from one end to the other)<br />
<br />
Please, please, please!!! Someone blew up his card by measuring resistance while it was on...lol. Good luck.<br />
<br />
(if you hook up the leads backwards...you'll get a - reading(or 0, depending on the multimeter you use). So you'll know. Just flip it around.</div>

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</div>Alright thanks guys, I'm glad somebody finally responded lol!<br />
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I'm gonna measure the vgpu and vmem right now with the + lead on each voltage register and the - lead on a grounded part of the GPU (bracket most likely)...<br />
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Everything sound good with this plan? lol
 

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Originally Posted by <strong>kidwolf909</strong>

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<div style="font-style:italic">Alright thanks guys, I'm glad somebody finally responded lol!<br />
<br />
I'm gonna measure the vgpu and vmem right now with the + lead on each voltage register and the - lead on a grounded part of the GPU (bracket most likely)...<br />
<br />
Everything sound good with this plan? lol</div>

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Your case should be a ground. Or, touch any black wire leading to your PSU. (BLACK ONLY!!!!)
 
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