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Author Topic: Weird Pots?  (Read 2776 times)

Offline 908ssp

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Weird Pots?
« on: November 06, 2006, 01:59:58 PM »
Hi Wilmington and Paul can one of you explain to me the weird pots in my Mojo? Traditional volume pots for a humbucker pickup are 500k but the one installed on my Mojo is only 20K and I measured it to be sure, yep 19.89k.

The reason I ask is I broke it yea got a knob stuck and when I pulled it off the shaft came right out of the pot. I am not going to make comments on quality pots no point. Anyway I replaced it without giving it a lot of thought with a 500k pot. Worked fine but after a few days it occurred to me this guitar seems too dark and I wanted to make it brighter. A common mod on traditional guitars is to up the ohms on the volume pot so I was looking into putting  1meg pot in. Thats when I checked the old broken original volume pot and found out it was only a 20k. Which seems very weird. Also the old dual volume pot from the Deluxe is a only 10k. Is the difference due to the mix control on the pre-amp? And if so what value can I replace the stock pot with?

Alex

Alex

[IMG]http://i146.photobucket.com/albums/r245/908ssp/ThumbNails/_1010802.jpg[/IMG

Weird Pots?

Offline rt0412

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Weird Pots?
« Reply #1 on: November 06, 2006, 07:48:17 PM »
quote:
Originally posted by 908ssp

Hi Wilmington and Paul can one of you explain to me the weird pots in my Mojo? Traditional volume pots for a humbucker pickup are 500k but the one installed on my Mojo is only 20K and I measured it to be sure, yep 19.89k.

The reason I ask is I broke it yea got a knob stuck and when I pulled it off the shaft came right out of the pot. I am not going to make comments on quality pots no point. Anyway I replaced it without giving it a lot of thought with a 500k pot. Worked fine but after a few days it occurred to me this guitar seems too dark and I wanted to make it brighter. A common mod on traditional guitars is to up the ohms on the volume pot so I was looking into putting  1meg pot in. Thats when I checked the old broken original volume pot and found out it was only a 20k. Which seems very weird. Also the old dual volume pot from the Deluxe is a only 10k. Is the difference due to the mix control on the pre-amp? And if so what value can I replace the stock pot with?

Alex


Most active circuits use pots with values like 10K, 25K, 50K.
20K pots are hard to find. Use a 25K pot, 'A' (Audio Taper) not 'B' (Linear Taper).

Suppliers from the top of my head are:
http://www.guitarelectronics.com (only sells audio taper pots)
http://www.guitarheads.net (sells A or B taper, specify A)
http://ww.stewmac.com (verify from stewmac that their 25K pot is audio taper)
http://www.tubedepot.com (sells A or B taper, choose A)
« Last Edit: November 06, 2006, 07:50:50 PM by rt0412 »
 

Weird Pots?

Offline 908ssp

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Weird Pots?
« Reply #2 on: November 06, 2006, 09:40:51 PM »
On the refined guitar the magnetic volume pot shouldn't be an active pot value. The Fishman Power chip is intended to be installed in conventional guitars to supply a preamp circuit for the many after market piezo bridges. It says nothing in the instructions about replacing the volume pot with one of different value. Weird.

I am not arguing just trying to reason out what is going on. Remember I have been running this guitar for 6 months at least with a 500k pot and it is working fine so a 20k pot is not needed for it to work. This is more of academic interest then anything else.

By the way my 96 Deluxe uses a 10k stacked double pot, 10k on each pot. Now that makes some sense since one of those pots is working the piezo volume.

Alex

Alex

[IMG]http://i146.photobucket.com/albums/r245/908ssp/ThumbNails/_1010802.jpg[/IMG

Weird Pots?

Offline rt0412

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Weird Pots?
« Reply #3 on: November 07, 2006, 03:27:36 PM »
How was the 20K pot wired? Was it connected directly to the MagPU selector switch or somewhere else, like a board or something? It's really weird because if the 20K volume pot was connected directly to the mags (through the toggle select switch) it would have sounded very muddy (no highs).
 

Weird Pots?

Offline 908ssp

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Weird Pots?
« Reply #4 on: November 07, 2006, 05:04:09 PM »
quote:
Originally posted by rt0412

How was the 20K pot wired? Was it connected directly to the MagPU selector switch or somewhere else, like a board or something? It's really weird because if the 20K volume pot was connected directly to the mags (through the toggle select switch) it would have sounded very muddy (no highs).



Exactly right that is why this is so weird. It was wired just like a traditional guitar to selector switch. Even has a high pass capacitor soldered to it to maintain highs when turning down the volume. Another thing noticeable different from the per refined guitar is that the tone cap is located on the tone pot just like a traditional guitar unlike the previous guitars where the cap was a sub miniature thing built into the board. [:0]

Alex

Alex

[IMG]http://i146.photobucket.com/albums/r245/908ssp/ThumbNails/_1010802.jpg[/IMG

Weird Pots?

Offline rt0412

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Weird Pots?
« Reply #5 on: November 09, 2006, 03:22:16 PM »
quote:
Originally posted by 908ssp

Exactly right that is why this is so weird. It was wired just like a traditional guitar to selector switch. Even has a high pass capacitor soldered to it to maintain highs when turning down the volume. Another thing noticeable different from the per refined guitar is that the tone cap is located on the tone pot just like a traditional guitar unlike the previous guitars where the cap was a sub miniature thing built into the board. [:0]

Alex


If you have a 25K pot, why not try it, just for the heck of it? I wonder if you'd get close to the "original 20K" sound...

Also, what is the value of the tone pot? Should be easy to measure in-circuit since the capacitor would not really affect the reading.
 

Weird Pots?

Offline 908ssp

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« Reply #6 on: November 09, 2006, 04:12:28 PM »
I played the Mojo last night with the 500k ohm pot and it sounded fine. The tone pot is 500k ohm. For some reason it didn't seem so dark last night.

[^]

Alex

Alex

[IMG]http://i146.photobucket.com/albums/r245/908ssp/ThumbNails/_1010802.jpg[/IMG