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 Post subject: 150k pots for MPC
PostPosted: Sat Jan 29, 2005 8:08 am 
hey guys i saw one post for this same subject and while looking around to replace all my pots i read something interresting and i'm hoping for some confirmation. while looking for pots the 500k are easy to find and looking at parts places they talk about the 1meg pot.
the quick: the pots funtion is to vary the amount of hot that is bled off to the ground....the school of thought is that more resistance makes the pickup hotter putting more gain the the amp....ok i can agree with this but will this same thought work for the MPC channels as well. IE going to a 250k pot for the MPC circuits or would this over load the effects units?
second does anybody have a really good replacement pick up for the open coill double humbucker?


 Post subject:
PostPosted: Sat Jan 29, 2005 3:47 pm 
thats so funny i went on e-baysaw 150 pots and in my furry made the purchase just to find out they were also smooth shaft...doht!
ok i went out to the music stores, did a ton of research and i believe this is a just answer
(for info i found no other 150k pots)
ok so now what can be used as a replacement which way should i go 200 or 100k. As it was described to me this specific circuit is designed for 150k now most pots have a +- of 20 % and here is the effect lets say everything perfect and only the pot having the variable that in this circuit the knob turned to "0" will effectivly make the resistance of the circuit 150 and essentially sending the current to the ground and deverting no sound to the effect (let say the dynamic fuzz) and thus a clean sound. turn the knob to 10 and the resistance is now zero thus all the signal is sent to the effect (full distortion)..ok so lets apply the +-20%
on the plus, the total resistance would be 180k thus allowing no signal at all ever reach the effect module.
applying the -20% the pot would have a total resistance of 120k and the result would be even with the knob turned to 0 some of the singnal would still reach the effect unit so you would still have a little distortion with the knob at zero.
so my conclusion that a substitute pot of 200k is perfectly fine and can be found on e-bay at this moment ... RK:MEWA:IT
for buy it now of $1.25
what this 200k pot will do is make sure that no signal will ever pass at the zero setting - BUT will cut out the signal around the one or two setting thus shortening the effective rage of the knob. the effect control would run fron 10 to 2. NOT that the full range of effect control is not accessable, it just only accessable over a shorter range of the dial.
meaning that where ever on the dial the resistance reaches 150k the signal will diverted.
and its unknown where on the dial this will happen until you try it.
just for giggles lets say we used a 100 the result is that the full dial could be accessed but you could never totally turn off the effect using the dial - but isn't that what the switch is for :) - your choice, but at least we now know the guitar won't blow up
and i must say i haven't made up my mind which way i'm going...........
Best of luck

PostPosted: Sun Jan 30, 2005 8:27 am 
i was also thinking about modifying a knob set as well
essentially the knurls in the knob would need to be drilled out using a 1/4" drill bit
then you would have to test set the pot turned to the off or "0" position
then align the knob on the shaft and it some way mark both the knob and the shaft of the pot.
where the mark on the knob is you would need to drill a 3/64th pilot hole at a 90deg to the pot shaft and use a 1/8th inch set screw with threaded bushing. the bushing would be a bit of a press fit with a touch of super glue to keep it set.
then where the shaft of the pot was marked using a file or grinding wheel, cut a flat spot into the pot shaft so that when the set screw in the knob was tighten it would not just spin on the shaft. this is a very common method of attaching knobs to pots on amps and other gutars.
Its just not as asthetically pleasing as the original method, as you would see the set screw sometimes when looking down at the guitar....but as i said many guitars and amps used this method...
I'm going to try both of these repares using a 200k pot and modifying the smooth shaft 150k pot, i'll take pictures and document the result and post them to this site for future reference.

oh the modle af gutar i have was an origial purchase by my father in 1981 and is the first guitar i learned how to play on....this guitar is priceless to me :)
a Vulcan X-940 in perfect condition - minus the dead pot to effect chamber #1

 Post subject:
PostPosted: Sun Jan 30, 2005 10:50 am 
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Joined: Sat May 22, 2004 12:17 am
Posts: 1903
check your PM!

 Post subject:
PostPosted: Sun Jan 30, 2005 2:05 pm 
Electraman wrote:
AP, any way to merge this with the other 150k thread or possibly close this one and refer people to the other?

I wish there was a way to! The next release of phpBB will likely have many new admin functions and hopefully merging threads is one of them.

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