what am i doing wrong with this POT?

[RichBa5tard]

I bought this (http://www.velleman.be/Product.asp?lan=1&id=8751) 10K pot to voltmod my R9500 (r9700 PCB desing).

I've set the resistance to 8K (should result in 1.6v gpu) and connected the middle pin to ground and one of the 2 other pins to leg #18 of the voltage regulator as described in MrIcee's guide.

When i turn on my computer, i get a whopping 2.4 vgpu (!)... that's a little too much for a 1.42v chip imho. I'm glad it survived. :)

When i check the resistance of the pot, it's about 300~400 ohm once connected, but when i disconnect the ground, it's back 8000 ohm... what am i doing wrong? Should i just buy a fixed 8k resistor to be safe? :confused:

I'm cooling the gpu with a 80W pelt & h²o, which is the highest _safe_ vgpu i can use, and how much ohm?

:am:

[Xenogias]

dude, smoke that :banana::banana::banana::banana::banana:.....thats what you're doing wrong with that pot. screw computers....

seriously, it sounds like (if you're using a cermet trimmer) that you have connected the wrong leg of the pot to the pin 18, giving you essentially 2000k ohms resistence (although you say 300-400, so this may not be the case). If this isn't the case, I'm not sure whats wrong. Just make sure that you test the middle leg (ground) and the leg you are going to solder to pin 18 with an ohmmeter, and if it registers 8k but you still get 2.4vgpu, make sure your measurement point is correct. Thats all i can tell you atm.

as far as highest safe voltage, I've run 1.92vgpu with an 80w pelt and warmish (35-40c) water, as i run it on a loop with a 226w pelt. The back of the gpu never got above room temperature. I wouldnt go much higher than that, and not for very long. 1.75v is highest i would consider safe for day to day use with a pelt. i run mine at 1.7 normally.

[RichBa5tard]

Well, i've used the right measuring point, because normally it's at ~1.42v: stock voltage.

When i disconnect the ground pin, the resisitance between the two legs of the pot is 8k, so i don't think i connected it the wrong way.

Ah, screw it, i'll just buy a fixed 8k ohm resistor. :)

Thanks for replying. :toast:

[Holst]

best way to work is to set the safe end of the scale then increase the voltage whyle measuring the voltage.

That pot isnt the right type either, you should be using a multitern cermet type pot, that way you cant knock it or ajust it too fast.

it sounds to me like you gave it 2k rather than 8k (I dont knwo how this mod works so I might be wrong) by using the wrong two pins.
You should buy a multimeter to test this stuff before you fit it.
A £10 multimeter or a £300 graphics card... an easy choice for most people.

or it might be that your card is different to the one you are copying, in which case a 8k fixed resistor might be just as bad.

[RichBa5tard]

i _have_ a multimeter and I _did_ measure the resisitance! It's 8k when not grounded, ~ 500 ohms grounded. I don't know why resistance changes as soon as i connect it. :confused:

Maybe it's just a broken pot.

I bought a 7 & 8k fixed resistor and it works great. 7k (6.8k actually) only gives me 1.5v though (stock: 1.42v).

[KS1]

Generally speaking, one would not get a correct reading of a resistor (resistance value) when it's connected on a circuit.

[RichBa5tard]

Originally posted by KS1
Generally speaking, one would not get a correct reading of a resistor (resistance value) when it's connected on a circuit.

aha, that's what i needed to hear. Thanks KS1. :)