Note on choosing a resistor for Vmod

[KS1]

I came across a spec (tolerance level) of each type of resistors that could be used to do the mod.

1. Cermet multi-turn: +/- 10%
2. Carbon film (fixed): +/- 5% or +/- 10% (gold or silver band)
3. Carbon pot: +/- 20%
4. Metal film (fixed): +/- 1%

Based on the above info, it could be said that a metal film resistor offers the lowest tolerance level and should be used to do the mod to min the flucuation/variation in volt.

Source: http://www.velleman.be/

[pelikan]

Thanks for posting that. I read it just before going to Radio Shack for resisitors and found the metal film ones there. But I wasn't sure how many watts the 1.5KOhm resistor should be for my Ti4600 core volt mod. I got 1/4 watt, but I'm going to make sure before I use it.

[KS1]

A watt rating is not as crucial as a tolerance level.
Generally speaking, a 1/4 watt is more than enough to do the mod.

[pelikan]

Cool. I'm going to throw that baby in there. Thanks.

[IamAnoobieCheez]

Great info, KS1. Thank you for your contribution.

[ppctx]

I would believe that the stated tolerance on resistors is the tolerance on getting exactly what the package says it is, not how much it jumps around.
Example:
You buy a 10k resistor either fixed or variable, is asserts a tolerance of 10%+/-, so you test it and are likely to find the actual resistance to between 9k and 11k but what ever that resistance is it stays their. Your ohm meter doesn't jump around from 9k to 11k... no, or did some prankster put a funny mushroom in my taco?

[wolfgang]

Originally posted by ppctx
I would believe that the stated tolerance on resistors is the tolerance on getting exactly what the package says it is, not how much it jumps around.
Example:
You buy a 10k resistor either fixed or variable, is asserts a tolerance of 10%+/-, so you test it and are likely to find the actual resistance to between 9k and 11k but what ever that resistance is it stays their. Your ohm meter doesn't jump around from 9k to 11k... no, or did some prankster put a funny mushroom in my taco?

thats what i thought

[KS1]

then will you buy a 1kOhm resistor to do vmod to find that it is running as a 800Ohm resistor?

as far as vmod is concerned, it is very critical in the amount of resistance value that we used especially for the first of its kind vmod that involved trial-and-error method.

[ppctx]

Originally posted by KS1
then will you buy a 1kOhm resistor to do vmod to find that it is running as a 800Ohm resistor?
as far as vmod is concerned, it is very critical in the amount of resistance value that we used especially for the first of its kind vmod that involved trial-and-error method.

yes, you could be using 800Ohms (if you bought a 1kOhm resistor with a tolerance of 20%) of resistance if you didn't check with a good multimeter before you used it. I hope all are checking and rechecking all of these tiny parts before being used for such critical things :p
For trial-and-error I would suggest a quality multi-turn Cermet that is dialed in for the exact resistance that was calculated to be needed. Then check and recheck to make sure you are putting in what is required. If the results are not what you expected, you can adjust the pot to achieve the desired effect.
But hey, thats the fun thing about moding, you can do it however you want.