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Help on Trimpot knowldge

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MaddMutt

Member
Joined
Jan 12, 2015
I have purchased a 100K & 5K Trimpot for my HD 4870 Voltmod.
I followed the required items needed as found here http://sandwichamwin.blogspot.com/2008/07/volt-modding-hd4870.html

Both of the trimpots have their knobs on top. Which way does it need to be turned to be in the OFF\LOW position?? Does the knob stop turning when you reach the end??

Here are pictures of the trimpots that I got.

100K Trimpot
Untitled #1.jpg

5K Trimpot
Trimpot 5K.jpg

Thank You For Your Time :)
 

Blaylock

"That Backfired" Senior Member
Joined
Jun 5, 2013
Location
Go Blue!
Those look slightly different than mine but probably function the same. for mine (10k) i had to have the trimmer turned fully clockwise(Max resistance) to set the vCore close to the BIOS setting. It probably depends on which two post you use on the pot also. You could always test it with a digital Ohm meter/multi-meter. DSCN3118.jpg
 

Lochekey

Senior Pink Member
Joined
Sep 13, 2015
I use pots similar to this. Like Blaylock said it will depend on which leg you connect. The center leg is the common and the two outer legs are the varied resistance. Depending on which of the two outer legs you connect to you will either have to go clockwise or counterclockwise so it is really up to you how you want to set it up. I draw an arrow with a plus sign on mine so that i remember which way is which after i have them wired up.
 

Blaylock

"That Backfired" Senior Member
Joined
Jun 5, 2013
Location
Go Blue!
^ This guy is smrt. I normally make sure to return it to the lowest setting before I'm done that way I'm not hammering volts while at ambient. LOL

M&M said:
Does the knob stop turning when you reach the end??
No it doesn't stop at either end but you can definitely feel when you reach the end. There is a tactile end.
 

Lochekey

Senior Pink Member
Joined
Sep 13, 2015
^ This guy is smrt. I normally make sure to return it to the lowest setting before I'm done that way I'm not hammering volts while at ambient. LOL

No it doesn't stop at either end but you can definitely feel when you reach the end. There is a tactile end.

The ones I bought do have a end stop. If you overcrank them you can break past it but there is a definitive stop. I wire in a microswitch in my setup as well so that I can leave my trimpots set and just turn them on and off.
 

Blaylock

"That Backfired" Senior Member
Joined
Jun 5, 2013
Location
Go Blue!
Something else to note MaddMutt is that even with the trimmer turned all the way down there was still a bump in voltage (0.064v) from the BIOS settings prior to adding the pot. Adding a micro switch like Lockekey may eliminate that, but it's something to be aware of.
 

Johan45

Benching Team Leader Super Moderator
Joined
Dec 19, 2012
Just check it with your multimeter only way to be sure which leg is off/on and what restistance you're getting. If you don't have a DMM get one
 
OP
MaddMutt

MaddMutt

Member
Joined
Jan 12, 2015
As I posted earlier. I'm following this guide to voltmod my HD 4870 http://sandwichamwin.blogspot.com/2008/07/volt-modding-hd4870.html

Hopefully it will not turn out like Lochekey's. I think a WILD cat hair might have caused yours to short :)

When using my DMM set @ 2K ohms and reading the 100k trimpot. Using the middle tab as common - The right tab reads .002 - The left tab reads .101 - Does this sound right??? I think this is turned all the way down for the middle\right tabs.
 
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Lochekey

Senior Pink Member
Joined
Sep 13, 2015
Can you set your DMM to 100k+ ohms instead of 2k ohms it will give you a more reliable reading.
 
OP
MaddMutt

MaddMutt

Member
Joined
Jan 12, 2015
Can you set your DMM to 100k+ ohms instead of 2k ohms it will give you a more reliable reading.

I have above the 2k spot - 20k, 200k and 2m. 200k gives me - Left 00.1 - Right 00.0

Reading package and it says 100 ohms, would that be the setting below 2k that reads 200??? With this setting I get - Left 99.7 - Right 00.7
 
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Lochekey

Senior Pink Member
Joined
Sep 13, 2015
Are you using 100K ohm or 100 ohm trimpots? The guide calls for 100 ohm and 5k ohm trimpots not a 100k ohm trimpot.
 
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MaddMutt

MaddMutt

Member
Joined
Jan 12, 2015
I'm using 100 ohm trimpot for the VGPU and 5k ohm for the Memory side.
 

Lochekey

Senior Pink Member
Joined
Sep 13, 2015
Ok earlier you mentioned using 100K ohm trimpots which is why I was second guessing your DMM readings. Based on this I would say that yes you have them set correctly all the way to one side.
 
OP
MaddMutt

MaddMutt

Member
Joined
Jan 12, 2015
How much mv does the 100 ohm give??
How much mv does the 5k ohm give??
Does the increase mv show up in Afterburner\Trixx. Do you turn up the trimpot while the card is powered up??
I don't want to turn it to far and fry the card :)
 

Blaylock

"That Backfired" Senior Member
Joined
Jun 5, 2013
Location
Go Blue!
I can't speak for the GPU, Lochekey is the guy for that, but on my mother board the Voltage change does show up in CPU-Z so I would venture to guess that it would for GPU-Z too. Turn the screws slowly to add just a little voltage at a time. Sometimes it takes a few turns before the voltage will start to change then just go slow.
 

Johan45

Benching Team Leader Super Moderator
Joined
Dec 19, 2012
How much mv does the 100 ohm give??
How much mv does the 5k ohm give??
Does the increase mv show up in Afterburner\Trixx. Do you turn up the trimpot while the card is powered up??
I don't want to turn it to far and fry the card :)

Voltage increases depend on the initial circuit voltage
You'll need live voltage read points to to verify V_GPU and V_Vram look at this pic after I took it I added another lead for the mem voltage readings. This is a lot easier than trying to touch spots on the card while it's running in a system
http://www.overclockers.com/forums/...9800GTX-Vmod?p=7950661&viewfull=1#post7950661
 

Lochekey

Senior Pink Member
Joined
Sep 13, 2015
My voltages do not show up in the software monitoring which is why I added the voltage readouts on the 7970 that I did.