100k pot made into 500k

[guavatone]

is there a way to convert a 100kohm pot to 500kohm with resistors?

I need to fix this horible TS-turbo

[cd]

Nope.

If you're using the pot to control the gain in a feedback loop, change the other gain set resistor and cap.

[petemoore]

100K +100K POT+ 300K = 500K
  are you using all the potlugs?
 200k +100k pot + 200k = 500k...using a linear pot set at half, you'd get 250k R on either side, turn the pot either way and one side gets 300k the other gets 100k...or 100k of variable resistance. Like turning a 500k from 11:30 to 12:30 or something like that....verify variables with DMM.

[cd]

100K +100K POT+ 300K = 500K
  are you using all the potlugs?
 200k +100k pot + 200k = 500k...using a linear pot set at half, you'd get 250k R on either side, turn the pot either way and one side gets 300k the other gets 100k...or 100k of variable resistance. Like turning a 500k from 11:30 to 12:30 or something like that....verify variables with DMM.

How the hell is that a 500k pot?  If you need to go from 0 to 500k, there is no way to make a 100k pot do that.  Add all the resistors you like, it won't happen.

[petemoore]

100K +100K POT+ 300K = 500K
  are you using all the potlugs?
 200k +100k pot + 200k = 500k...using a linear pot set at half, you'd get 250k R on either side, turn the pot either way and one side gets 300k the other gets 100k...or 100k of variable resistance. Like turning a 500k from 11:30 to 12:30 or something like that....verify variables with DMM, >>>some range but limited compard to a 500k.
 .

How the hell is that a 500k pot?  If you need to go from 0 to 500k, there is no way to make a 100k pot do that.  Add all the resistors you like, it won't happen.

>>>I don't have time to explain. You'll be ok. Just re-read it if you're still confused, AND do nOt forget to verify resistances with a DMM cd.
 Also, I should say use a 500k pot for proper range, again what circuit. 100k pot and 8 x 100k resistors and switches could get you everything from 0-500k...alot of messing around. Basically you only get 1/5th range [100k of 500k], anywhere in the 500k range...100k through 200k, 200k through 300k, 300k through 400k, or 400k through 500k, depending where it's placed in the string of four seriesed 100k resistors...long story short...use a 500k, or 1meg pot with a 500k resistance from wiper to each outside lug.
 Sometimes, for tuning bias or something, 100k variability 'within' a 500k string [right in the middle] is enough to do the trick. Other times you may need 500k resistance across the pot, but leave the pot set, so finding you're sweet spot resistance could be easier using a smaller pot than you'd like to use [cause you don't have a big one] and finding the sweet spot by 'course targetting' first where the 100k sits in the string, then fine tuning when you get close to the target.
 Alot of how much you 'actually' need the big pot you don't have depends on how you're using it in what circuit.
 What circuit is this being used in and in what capacity?

[cd]

100K +100K POT+ 300K = 500K
  are you using all the potlugs?
 200k +100k pot + 200k = 500k...using a linear pot set at half, you'd get 250k R on either side, turn the pot either way and one side gets 300k the other gets 100k...or 100k of variable resistance. Like turning a 500k from 11:30 to 12:30 or something like that....verify variables with DMM, >>>some range but limited compard to a 500k.
 .

How the hell is that a 500k pot?  If you need to go from 0 to 500k, there is no way to make a 100k pot do that.  Add all the resistors you like, it won't happen.

>>>I don't have time to explain. You'll be ok. Just re-read it if you're still confused, AND do nOt forget to verify resistances with a DMM cd.
 Also, I should say use a 500k pot for proper range, again what circuit. 100k pot and 8 x 100k resistors and switches could get you everything from 0-500k...alot of messing around. Basically you only get 1/5th range [100k of 500k], anywhere in the 500k range...100k through 200k, 200k through 300k, 300k through 400k, or 400k through 500k, depending where it's placed in the string of four seriesed 100k resistors...long story short...use a 500k, or 1meg pot with a 500k resistance from wiper to each outside lug.
 Sometimes, for tuning bias or something, 100k variability 'within' a 500k string [right in the middle] is enough to do the trick. Other times you may need 500k resistance across the pot, but leave the pot set, so finding you're sweet spot resistance could be easier using a smaller pot than you'd like to use [cause you don't have a big one] and finding the sweet spot by 'course targetting' first where the 100k sits in the string, then fine tuning when you get close to the target.
 Alot of how much you 'actually' need the big pot you don't have depends on how you're using it in what circuit.
 What circuit is this being used in and in what capacity?

Did you bother reading the original post?  This is a TS9DX, the pot is used to SET THE GAIN OF THE OPAMP.  It's wired as a rheostat, NOT a voltage divider.  You need the full range of the 0-500k, not some fake 10 degree rotation BS.   Early TS9DXs had the wrong value for the drive pot.  If you want to get back the full range, you either change the gain set resistor (coming off the - input), change the pot, or do a "pot mod", seen here:

http://www.geocities.com/SunsetStrip/Vine/6655/tubescreamer.htm

[Hal]

everyone needs to _calm_ down.

You're both right....yes, it can't make a "real" 500k pot, yes, it can do something fairly useful, maybe.  He can use it to test out the circuit in a jam, while the parts in the mail or something.

[petemoore]

Anyway, when you just had coffee and want to see what happens...
 You take a couple test clipped wires [2 clips on a wire], a handful of resistors and a pot.
 Use a knob, maybe put a cardboard mount to mark left right and center settings of your pot.
 Measure the pot. put different value resistors:
 wiper to outside lug[s
 across the outside lugs [1 and 3]
 from outside lug[s to meter
 Might as well take notes so you'll know about where you'll get in future tapering tasks.

[cd]

Hal, I can appreciate you trying to diffuse things, but the fact of the matter is, if you need a 500k pot to sweep from 0 to 500k, as it is in this case (to go from zero distortion to full distortion) there is NO WAY to do it with a 100k pot and resistors.  Tack a 400k resistor onto the end, the best you're going to get is 400k to 500k, or some other 100k sweep in between.  Which means unless you're in love with one particular 10 degree rotation of the control, adding other resistors is useless.

If I sound emphatic, it's because this is a frequently confused topic which always requires clarification.  Fundamentally, you can put resistors across any combination of lugs you like (1>3, two resistors 1>2, 2>3) it won't make the pot any larger.  Remember the forumula for resistances in parallel:

(R1*R2)/(R1+R2)

The parallel resistance can never be larger than the smallest resistance.  Think about it: two 10k resistors in parallel = 5k.  As one resistance increases towards infinity (some very large number) you have 10k*(some very large number)/(some very large number), and the parallel resistance approaches 10k, but never exceeds 10k.

In short, replace the pot or do the pot mod.

[guavatone]

Thanks cd.  I did that mod but I wasn't really satisfied with the drive.  

Does antone know where to get a 500k pot replacement.  Its a "square pot that measures 9.6mm x 10.9 mm.  It sits at a 90 deg agle to the PCB.



Thanks

[petemoore]

Mouser has little 16mm ones...hope this helps.

[Brian Marshall]

you could use an led, and two matched reciprocating LDR's.  That might be kind of hard to do because i doubt they would totally be linear.

[Paul Marossy]

You could try taking a 1M pot and soldering a 470K pot across the lugs to make a rough 500K pot...

[puretube]

errr, put a 1M across the lugs to make it 500k... :wink:

[Paul Marossy]

Doh! That's what I meant to say...  :oops:
For some reason I always say it that way - the end result. But it's actually the same value as the pot. Thanks for correcting me on that, puretube.

[Jason Stout]

You can make a 100k pot into a fully functional 500k pot. Just find a way to open it, remove the resistive element, gently sand with fine steel wool until the strip measures 500k, rinse well and re-assemble. Check Small Bear's Tremulous bear doc for a picture essay. If you have a pot you can open, its not hard at all.


http://www.smallbearelec.com/Projects/TremBear/TremBear.html