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Whats This Variable Resistor Called?

11/08/2014 6:53 PM

Whats this variable resistor called? Its a volume control on a radio and I have measured a few of the contacts and they vary in an analog way as you turn the shaft. Whats this type called and why so many contacts.Thanks for reading.

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#1

Re: whats this variable resistor called?

11/08/2014 7:28 PM

It looks like a potentiometer with several channel control....

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#5
In reply to #1

Re: whats this variable resistor called?

11/08/2014 8:41 PM

Thanks for reply SolarEagle.

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#2

Re: whats this variable resistor called?

11/08/2014 7:36 PM

It is hard to say from that picture. An actual schematic would help but I realize that may not be possible. If there are only the nine inline contacts I see then my first guess is that this might be three ganged potentiometers controlled by one shaft. Another possibility is two ganged potentiometers and one form C switch. With this being an audio circuit it may or may not have a linear taper.

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#6
In reply to #2

Re: whats this variable resistor called?

11/08/2014 8:42 PM

Thanks for reply Redfred. I dont have a circuit diagram for this... wish I had. Will probe it more with my meter.

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#3

Re: whats this variable resistor called?

11/08/2014 7:40 PM

It is a potentiometer, but instead of a smooth sweep, it has multiple steps in resistance. I've seen these used in high-end stereo equipment to reduce noise.

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#4
In reply to #3

Re: whats this variable resistor called?

11/08/2014 8:40 PM

Thanks. It is high end equipment. I will do more testing with my meter. I wish I knew what its called because then I could look up datasheets. Not that its faulty... just curious.

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#11
In reply to #3

Re: whats this variable resistor called?

11/09/2014 11:15 AM

Actually, steeped attenuators need a large number of external resistors (either through-hole or SMT) and a rotary switch.

This doesn't look like quite like a stepped attenuator to me.

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#12
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Re: whats this variable resistor called?

11/09/2014 12:14 PM

Many high-end audio equipment today use an incremental encoder instead of a potentiometer for a manual control knob. This makes it easier to interface a remote control and reduces the analog signal path to limit interference noise.

I agree with AH. This is likely not a stepped attenuator volume control because there are not enough contacts.

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#13
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Re: whats this variable resistor called?

11/09/2014 1:43 PM

That and if you follow the link in my Post #9 you will see a picture and schematic for a pot that looks almost exactly like the one pictured.

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#7

Re: whats this variable resistor called?

11/08/2014 9:07 PM

Is it analog, or binary stepping? 6 pins plus power (7 pins), and gnd is metal case.

So it would be a 6 bit binary counter. Most likely gray code and not a linear binary count.

See if the pins change as digital state.

Also look at the IC this is connected to. If you can find the data sheet for that chip see what the volume control input is.

It does not make sense that it would be a dual resistor type volume control with a single shaft.

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#8
In reply to #7

Re: whats this variable resistor called?

11/08/2014 9:24 PM

The first thing I thought when I saw it was that is a stepping thing... but a limited probing with ohmeter shows analog changes in resistance as shaft is turned. I suspect vermin (dont like calling a person that really) is onto the right answer. I will do more probing later and thanks for tip on looking at what its hooked to.

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#9

Re: whats this variable resistor called?

11/08/2014 11:02 PM

It's simply a PC board mount stereo analog pot. Nothing more.

That accounts for 6 of the terminals and the 7th is just a dummy pin.

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#10
In reply to #9

Re: whats this variable resistor called?

11/09/2014 7:50 AM

Super. Thankyou Anonymous Hero.

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#14

Re: Whats This Variable Resistor Called?

11/09/2014 11:04 PM

In order to know more, you can see the datasheet of the IC it is connected to.

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#15

Re: Whats This Variable Resistor Called?

11/10/2014 4:07 PM

ROTARY ENCODER...not a pot.

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#21
In reply to #15

Re: Whats This Variable Resistor Called?

11/25/2014 10:25 PM

See photo I posted in answer to another post further on. Carbon tracks!

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#16

Re: Whats This Variable Resistor Called?

11/10/2014 4:32 PM
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#17

Re: Whats This Variable Resistor Called?

11/12/2014 12:16 PM

Appearances are that it is an analogue audio potentiometer, I performed a search at Mouser and there are pages of options. With some circuit data a search can be performed and it is likely a OEM replacement if needed can be found.

I invite you to check the location below, photo's and specs are available, there are hundreds of options.

http://www.mouser.com/Passive-Components/Potentiometers-Trimmers-Rheostats/_/N-9q0yi?No=100&P=1z0z54uZ1yzvm31

Have a fantastic day!

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#18

Re: Whats This Variable Resistor Called?

11/13/2014 9:53 AM

Does the shaft have stops when rotated clock-wise and counter-clockwise? If yes, then it's probably a potentiometer as mentioned, if it does not have stops, then it's probably a rotary switch or as one person mentioned, a "rotary encoder". Even with stops it could be a rotary switch, but they are less common. The fact that it has 7 terminals (and maybe some on the opposite side that can't be seen.) makes me doubt that it's just a stereo potentiometer. For something like this, it would be common to have a momentary switch included, with contact being made by pushing the shaft in towards the PCB. Too many unknowns at this point. What kind of device is the PCB from, and maybe most importantly, if this is an external control, what is the knob labeled that goes to this device?

Tom D.

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#19

Re: Whats This Variable Resistor Called?

11/14/2014 1:41 PM

Hang on a second, you say that you probed this with your multimeter. Did you do this with the unit still in the circuit or did you unsolder it and then probe it? Remember that any measurements of a device still in a circuit will reflect everything that it touches, and the readings will be different if the circuit is powered or not.

Why not help us solve your mystery by revealing the make and model number of the stereo, you'll get a more informed answer very quickly.

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#20
In reply to #19

Re: Whats This Variable Resistor Called?

11/25/2014 10:23 PM

If it had any numbers or make on it I would have reported that in my post. I did in the end find an identical one in an identical bit of equipment (Roberts DAB radio RD50) The way the internal tracks are connected is really complicated... not a nice simple double pot at all. Thankyou for your reply.

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#22
In reply to #20

Re: Whats This Variable Resistor Called?

11/25/2014 10:30 PM

I did try to find the schematic for that radio and as far as I can see it just is not to be had anywhere so I suppose that was why I did not say make and number of radio but I suppose I should have anyway. Thankyou for your input.

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Anonymous Hero (3); Bill H. (1); daffy (1); gmphadte (1); ignator (1); Jrod.Brown (1); RAMConsult (1); redfred (2); SolarEagle (1); Tank Circuit (8); tdesmit (1); vermin (1)

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