If the original resistance between pin 8 and ground is 4,5kohm you need a potentiometer(VR) with a much higher value than 4,5kohm to do the mod, because connecting resistors in paralell makes the resistance lower. That's why we usually multiply with 20.
You can use this formula to calculate the new resistance when connecting resistors in paralell: R=(R1*R2)/(R1+R2)
So if you connect a 100kohm VR in paralell with the 4,5kohm resistance between ground and pin 8 of the regulator chip you get: R=(4,5kohm*100kohm)/(4,5kohm+100kohm)=~4,3kohm. As you see, not a huge difference. If you used a 50kohm VR instead of the 100kohm you would get 4,12kohm, which would work too, but you woud get a higher voltage at the lowest setting.
You've circled the VR/potentiometer that I use to control vdimm on that pic.
This mod should work for your board:
Connect 100k VR between ground and pin 8 of the W83320G. You might have to turn the VR many times before the vdimm starts increasing, so be careful and watch the voltage.
Reply With Quote
Bookmarks