Identify rotary encoder or potentiometer?

Question

I'd like to fix my old receiver/amplifier. It has a broken button "balance", but after opening and extracting the component I have no idea what I should buy to replace it. From my point of view, it should be a potentiometer, but some people say that it is a rotary encoder.

In any case, there is no idea what to order; I googled the numbers, but I did not find anything that would match. Please see attached photos, which hopefully will help.

Following the advice of @Justme, I found: R393 Part No. 5104225 Description N11RGLC250KW22Z Variable, but again Googling does nothing, and searching Mouser for the part number gives "Thick film resistor".

I'm attaching a part of the schematics. It seems that it strongly resembles the Bourns PTT111 model, but Bourns does not produce 250k Ohm potentiometers. Only 200k and 500k. Is there anybody else who produces such a type of potentiometers?

It seems that the manufacturer is ALPS.

Answer 1

As fuzzy as the schematic image is, it is very clear. That is a single (not stereo), linear, 250k potentiometer with a center-tap on the element. This was and still is a very common way of implementing the balance function.

The pot also might have a mechanical detent at the middle of its range of rotation, to make it easier to set it to the center position where the left and right signals have the same attenuation.

The center-tap contact probably is connected to GND, but we need more of the schematic to confirm that. Also, there probably is an acceptable range of values, but again, more schematic.

Note that the signal line from the bottom of the pot, going to destination "Roh", is not connected to GND. That is not a connection dot below the pot as it crosses the GND; it is a printing/copying artifact.

Answer 2

If it is a rotary encoder: Do you get a short or low resistance measurement from between two pins (difficult to say exactly which) and then open circuit when you turn the knob step by step?

If it is a potentiometer: 225 would indicate 2.2 Mohm resistance (22 x 10^5). Following the same logic 523 = 52 kohm.

If you have a multimeter measure if you can find one of those resistances between the pins.

Then leave the multimeter connected to one pin and see if there is a changing resistance on another pin when you turn the shaft.

When the shaft is midway through it's movement there is either total resistance divided by 2, in which case it's a linear potentiometer. If the resistance is less than half of total, the best guess is that it's logarithmic type.

Last pin might be for a push function or it could have a fixed resistance to one end of the resistive element or some other function, can't be sure without exact identification of the part.

Answer 3

As @AnalogKid correctly said: "That is a single (not stereo), linear, 250K potentiometer with a center-tap on the element". After further research I found that it is an Alps Alpine discontinued product, and it seems there is NO direct replacement.