ATI 4850/4870 voltmod thread

[Death909]

Will this 200k variable resistor do for a 4850 volt mod

http://cgi.ebay.com.au/200k-Variable...QQcmdZViewItem

If not can i use a normal 1k resistor for a volt mod or not?


And the final question whats a good store to buy variable resistors from, preferably in Australia

Internet wisdom is that you need at least 10 turn or preferably 20 turn trimmer. The one in the ebay link doesn't look like it could even get a full turn in.

A normal 1k resistor will not give you any control / fine tuning, and depending on your card may actually kill it. If the feedback resistance is ~5k (like reference designs), a suitable trimpots would be 5x20 = 100k.

Jaycar sells trimpots (10 turn 100k) (25 turn 100k).

measure the resistant from pin 19 + ground, multiply x20 and this is the VR you need

Uh, yes. I understood that, and mentioned that the resistance from pin 19 to ground is ~9.58k. I'm only lacking tools and components. That and Jaycar doesn't appear to stock 200k trimpots. I still have to measure pin 6 to ground on the RT8105 though. Wouldn't mind having a rough idea of how much the voltage would increase when resistance goes from 9.58k to 9.15k (9.58k and 200k trimpot (set to max) in parallel).