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What would I refer to this type of potentiometer as?


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So like a volume pot that goes 1-10 would be called a linear pot. Is that correct?

 

What do you call a pot that has a detent in the middle and goes from 1 in the middle to 5 and -5. 

 

Dors that make sense? Like a blend pot i guess? 

 

Specifically a tone pot that boost or cuts 

 

Cheers, lads.

 

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Posted (edited)

As I understand it ...

 

The term linear is one that describes how the pot resistance changes relating to its position (Its taper) , the following is roughly how it works.

image.png.21a22146189108620e559e15fceb1b42.png

A center detent pot has a physical notch or dimple such that when it is moved to the centre position you get that little 'click' to indicate such, the electrical behaviour of the pot remains the same.

 

A common blend control is actually two pots with a single control shaft, as you turn the signal going through one pot increases whilst the other one decreases.

 

I believe a centre detent pot used to boost/cut requires some more electronics behind it (commonly active electronics) to achieve that effect.

 

Sam x

Edited by SamIAm
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3 hours ago, SamIAm said:

As I understand it ...

 

The term linear is one that describes how the pot resistance changes relating to its position (Its taper) , the following is roughly how it works.

image.png.21a22146189108620e559e15fceb1b42.png

A center detent pot has a physical notch or dimple such that when it is moved to the centre position you get that little 'click' to indicate such, the electrical behaviour of the pot remains the same.

 

A common blend control is actually two pots with a single control shaft, as you turn the signal going through one pot increases whilst the other one decreases.

 

I believe a centre detent pot used to boost/cut requires some more electronics behind it (commonly active electronics) to achieve that effect.

 

Sam x

Cheers. So i need to specify a centre detent pot!

 

It is an active preamp 

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Are you replacing an existing pot?  It could be logarithmic or linear either side of the detent.  Are there any legible identity codes on the pot?  If not you have four possible ways forward. 1. Ask the manufacturer what pot is fitted, 2.Search the internet for a schematic or clone schematic which might show the pot type, 3. Make some basic measurements, using a multi-meter and determine if the pot is log or lin, 4. Buy a log and a lin centre detent pot.  Try them both and see which you like.  What preamp is it? the BC collective wisdom may know the answer to your question.

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13 hours ago, 3below said:

Are you replacing an existing pot?  It could be logarithmic or linear either side of the detent.  Are there any legible identity codes on the pot?  If not you have four possible ways forward. 1. Ask the manufacturer what pot is fitted, 2.Search the internet for a schematic or clone schematic which might show the pot type, 3. Make some basic measurements, using a multi-meter and determine if the pot is log or lin, 4. Buy a log and a lin centre detent pot.  Try them both and see which you like.  What preamp is it? the BC collective wisdom may know the answer to your question.

20240623_022320.thumb.jpg.3f7a8c2d2147f6fca4f75022ac41789d.jpg20240623_022413.jpg.7ed90d8f9f0e7a5a1d23bb9dd6f1d00d.jpg

 

It's this fella. Treble boost from a 90s ibanez BII preamp

 

Any way i can tell what i need?

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Posted (edited)

A quick search does not find any schematics for a BII pre-amp. However, this circa 2008 looks promising https://www.talkbass.com/threads/fyi-ibanez-sr480-preamp-schematic-jpg-pdf.455174/.  The pot values are shown as 50K Ohms. I would imagine that the amp designs would not have changed much in that era, you could look which IC is fitted - TL062?   On the treble pot board, can you see what value the capacitor has on the side, and what colour code and hence resistance the resistor is.  This will help confirm that it is the schematic above.  The best answer would be to desolder the pot and then measure the resistance across the two outer legs.  

Edited by 3below
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Posted (edited)
59 minutes ago, 3below said:

A quick search does not find any schematics for a BII pre-amp. However, this circa 2008 looks promising https://www.talkbass.com/threads/fyi-ibanez-sr480-preamp-schematic-jpg-pdf.455174/.  The pot values are shown as 50K Ohms. I would imagine that the amp designs would not have changed much in that era, you could look which IC is fitted - TL062?   On the treble pot board, can you see what value the capacitor has on the side, and what colour code and hence resistance the resistor is.  This will help confirm that it is the schematic above.  The best answer would be to desolder the pot and then measure the resistance across the two outer legs.  

Looking at your images confirms it is not the above circuit, the treble capacitor on your board is C6, on the schematic it is C3.  Must look more closely at the evidence in future :(  Having said that there is no reason why the RC combination in that circuit could not have been used in other preamps.

Edited by 3below
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56 minutes ago, 3below said:

Those appear to be 20K, 19.8K + 0.2K.

Does that mean the pot is 19.8 and the little black thing is .2?

 

 

 

 

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52 minutes ago, 3below said:

Looking at your images confirms it is not the above circuit, the treble capacitor on your board is C6, on the schematic it is C3.  Must look more closely at the evidence in future :(  Having said that there is no reason why the RC combination in that circuit could not have been used in other preamps.

Cheers, bud.

 

I dont know any of this!

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Posted (edited)
4 hours ago, lidl e said:

Does that mean the pot is 19.8 and the little black thing is .2?

 

 

 

 

The little black thing with a stripe is an electrolytic capacitor.  The pot (in the model circuit) is 20K.  The best bet is to de-solder the pot and remove it from the little board.  You will have to do this anyway to replace it, de-solder braid and or a solder sucker are useful.  Get a multimeter (a cheapie  10-12 Euro one will do), and measure the resistance between to two outside terminals (legs).

Edited by 3below
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1 hour ago, 3below said:

The little black thing with a stripe is an electrolytic capacitor.  The pot (in the model circuit) is 20K.  The best bet is to de-solder the pot and remove it from the little board.  You will have to do this anyway to replace it, de-solder braid and or a solder sucker are useful.  Get a multimeter (a cheapie  10-12 Euro one will do), and measure the resistance between to two outside terminals (legs).

So that's a cap like on my fender basses. Like the .047 

 

The little PCB is just a design choice? One could achieve the same idea without it?

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51 minutes ago, lidl e said:

So that's a cap like on my fender basses. Like the .047 

 

The little PCB is just a design choice? One could achieve the same idea without it?

Yes and yes, although the PCB makes the construction simpler / neater / easier  than point to point wiring when you are manufacturing thousands (or more) of the preamp.  Stating the obvious, when you re-build it you will solder the new pot onto the PCB.

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1 hour ago, 3below said:

Yes and yes, although the PCB makes the construction simpler / neater / easier  than point to point wiring when you are manufacturing thousands (or more) of the preamp.  Stating the obvious, when you re-build it you will solder the new pot onto the PCB.

 

Which is also a reminder that you need a pot with PCB mounting terminals in the same orientation:

 

potentiometer.jpg

 

and not one with solder terminals

 

SF-COM-09939.jpg

 

or right-angle terminals

 

3233-Lg.jpg

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So it does look like it is a 20k. Does the 17 C on the other side mean anything?

 

Can you tell what value the cap is from these pics?

 

 

20240707_235953.thumb.jpg.549f4e9da5dd938f343969808e84f333.jpg20240707_235813.thumb.jpg.ac37cfe8a37252aada473b377738ddf8.jpg20240707_235749.thumb.jpg.b1d4fd4abd0e62e9d9767d9fb3f023b0.jpg

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10 hours ago, SamIAm said:

This schematic claims to be for that EQ and it shows a 20K pot.

https://everycircuit.com/circuit/5314341701681152/active-2-band-bass-guitar-eq-

 

Also, this post has some more info
https://www.talkbass.com/threads/1990-ibanez-sr1000-wiring-help.1089289/post-16157750

 

Sam x

I was looking at that EMG BTS as i think that is basically the same as this Ibanez BQ-II. 

 

But when icgot the bass back, it sounds so good, i want to try and get this one sorted.

 

It does have EMG pickups.

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17C may be manufacturer's date code or similar. 20 kohm is clear. Other alphabets are non standard, as there are many different ways of telling things: "A" may be "audio taper" i.e. logarithmic, but it can also be linear.

 

That C6, you took a picture from the other side only which says 85 degree centigrade. This is the max temp it works. The numbers on the other side tell the parametres needed.

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