Electrical – How to test a slide potentiometer

potentiometer

I have a slide potentiometer for a volume switch that I suspect is failed. I diagramed out the connections in the image below. The potentiometer is on the top part of the image with the outputs pins on the left, and the input pins on the right. I'm reading the following resistances between these pins from the slider pot (negative lead to output side on left of image, positive lead to input side on right of image), one measurement with the potentiometer slide all the way to the left, and the other all the way to the right which I believe is supposed to be full volume:

+Lead:-Lead    Ohms Leftmost   Ohms Rightmost
   R+:R-         11.67K          11.67K
   R+:Y          11.67K          9.9
   R+:L-         OL              OL
   R+:OR         OL              OL

   L+:R-         OL              OL
   L+:Y          OL              OL
   L+:L-         OL              OL
   L+:OR         OL              OL

If I'm not mistaken do these measurements demonstrate a fault with the left channel?

PCB Master Volume Switch
Master Volume Switch

Background

I'm troubleshooting a faulty Yamaha Keyboard (CLP-550), and I've roughly traced the signal with a multimeter to the master volume switch which is a slide potentiometer. It's labeled as a Yamaha VB022400 Slide Pot. A10KX2 RSGA2 MASTER VOLUME. I found hits on the A10KX2 ID which brings up a bunch of audio hits with mixer boards and what not so it looks like a good generic ID for the part. The left speaker's don't play audio so I'm hoping it's just this one part that failed since the signal seems to come out the main circuit board from both sides, but nothing after this volume control. Is my pin to pin resistance measurements a definitive test, is there something else I could try or may have done wrong?

Also is there a way to parse any info from the A10KX2 I recognize the 10K OHM from my leftmost measurements, is the X2 basically saying two channels or something, does the A indicate anything? Perhaps audio?

Update

Turns out the modern equivalent part number for this component is the VK369300 POTENTIOMETER A10K CLP/CVP. I soldered in the new part and now both left and right channels are operating properly so indeed the slide pot went bad.

Best Answer

I'd say that you are correct that the pot is faulty. No other component failure would give 'OL' readings on the meter at your test points.

The circuit is a little strange. Neither end of the pot is directly grounded on this board. For a standard volume control it would be most unusual to have resistors or capacitors in the ground leg of the potentiometer. This makes me suspect that R+ and L+ are the actual grounds. You should be able to test this by pluging back together and checking for continuity between the points on the board and signal ground - maybe on the audio out connector.

I can't help with part number diagnostics. I gave up on tracing Japanese parts in the pre-Internet days. Maybe it's easier now.

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