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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets.

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Old 7th Jan 2020, 10:36 am   #1
Michael Maurice
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Default Log potentiometers with taps

As you probaby know, log pots with taps are no longer available.

Even Blore Edwards cant make them.

I was therefore thinking of simulating one using either a dual pot for mono or 4 ganged for stereo (assuming there is room to fit it.

Can anyone think of a way this could be done?
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Old 7th Jan 2020, 10:49 am   #2
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Default Re: Log potentiometers with taps

If you search for "potentiometer loudness" on eBay you'll find lots of pcb mounting ones in the 'Alps' style, and some ready made boards with 'round' 100k ones.

https://www.ebay.co.uk/sch/i.html?_n...sPageName=GSTL

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Old 7th Jan 2020, 12:15 pm   #3
sortedradio
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Default Re: Log potentiometers with taps

There are several type of tapped log pots available for jukeboxes from https://www.jukebox-world.de/index.p...=potentiometer . They are not cheap, but may be of help.
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Old 7th Jan 2020, 2:27 pm   #4
Alistair D
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Default Re: Log potentiometers with taps

Post #5 in this thread has an alternative suggestion for a tapped pot.

https://www.vintage-radio.net/forum/...d.php?t=126515

Al
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Old 7th Jan 2020, 7:01 pm   #5
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Default Re: Log potentiometers with taps

Hi, how important is it that you have a tapped pot? The main use for one as I understand is the original baxandall tone control design.
Anyway I had a think and if its really important you can adapt/alter a switched resistive attenuator of which several types are available and not too expensively on the Auction site.
I have one here that I've had for years, 100k log 23 position switch that switches in individual pairs of resistors in a potential divider rather than a shunt or simple ladder configuration. Each switch tag is easily accessible so you could place a tap wherever you want it along the 23 positions. With effort it could easily be converted to a linear control by replacing the individual resistors.
If you'd like to have a play with it then drop me a PM, I won't want anything for it if it's going to be useful to you.

Andy.
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Old 7th Jan 2020, 11:12 pm   #6
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Default Re: Log potentiometers with taps

One thing I didn't mention is that in the machine that i'm repairing, the volume control with a tap also has a mains switch on it!
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Old 9th Jan 2020, 12:33 am   #7
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Default Re: Log potentiometers with taps

Quote:
Originally Posted by bikerhifinut View Post
Hi, how important is it that you have a tapped pot? The main use for one as I understand is the original baxandall tone control design.



Andy.

The tap is needed for the shape/loudness/contour switch. The Pye BB circuit is fixed, this is switched.
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Old 10th Jan 2020, 12:23 am   #8
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Default Re: Log potentiometers with taps

Here is a circuit of the pot in question.

How could one incorporate the shape switch into a dual or quad log pot. Thats what I'm having difficulty with.

Remember this is also got the mains on/off switch, so I cannot use any of the alps type pots.
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Old 13th Jan 2020, 4:22 pm   #9
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Default Re: Log potentiometers with taps

Some people add their own custom taps using conductive paint.
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Old 13th Jan 2020, 5:32 pm   #10
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Default Re: Log potentiometers with taps

Quote:
Originally Posted by Michael Maurice View Post
One thing I didn't mention is that in the machine that i'm repairing, the volume control with a tap also has a mains switch on it!
I think you'll have to take it apart and repair it Michael. I've done dozens out of Jukeboxes and they often have 2 taps per track and many are stereo pots.
What is wrong with the old one?
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Old 13th Jan 2020, 6:32 pm   #11
David G4EBT
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Default Re: Log potentiometers with taps

As referred to by Al in post #4 above, you might wish to consider the option at the forum link he gave.

To save going to the other link, the circuit is attached below.

Blore Edwards can supply a dual gang log pot with mains switch (Type 2AR-45) here:

https://www.blore-ed.com/series45potentiometers
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Old 14th Jan 2020, 12:58 pm   #12
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Default Re: Log potentiometers with taps

I have such a pot, ganged 22k tapped at 9k with a double pole switch.A short plastic shaft,D'ed 1 inch long. NOS(not a solder onto PCB type) if you are interested I'll send you a pic via PM,Les
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