JVC RC-M70JW - Left volume slider always on MAX volume once it's 1/2 way up, right slider works perfect

[Tinkererman]

Hi Guys,

I picked up a nice clean JVC RC-M70JW recently, every slider works perfect except one, the LEFT Volume control.

The Left slider doesn't respond at all, no sound at all until you hit the half way mark and then BAM, it is on MAX volume as it will not get any louder as I push it up towards the MAX, it stays the same, FULL BLAST, but if you back it down just a hair, it has ZERO left channel volume.
I've never had a slider do this type of thing, kind of strange.

So when it does that, I move the right slider up to match the left channel volume level, and indeed it is on Max Volume.

The right slider volume works perfect through it's entire travel range from minimum to maximum as it should.

All other sliders work great, Bass and Treble respond well through their ranges etc., I have yet to clean any of them as I just got this.

Looking for thoughts on this issue as I have never even heard of it, so the left channel slider is either full bore volume or no volume.
As soon as the slider hits the mid-point in it's travel, it's on MAX, but no volume at all until you hit that mid-point in it's travel.

Thoughts? Shorted out? Cracked board, weird for sure. I've had a bunch of these apart in the past, so I'm not afraid to dive in deep.

I thought maybe someone has run into this issue at least once??

Thank you all for any and all replies, Rich

 

[Tinkererman]

It's a really clean unit also, must have been stored in a clean dry place for decades.

 

[Superduper]

The internal slider feeler contacts have detached internally from the main nylon slide block. New parts are no longer available. You will have to rebuild that slider by disassembling it, reaffixing the loose or detached contact. If you continue to operate the slider, you risk damaging or mangling that part where it is beyond repair since it's either going to get crushed by the nylon block, or it will get dragged and scratch or grind off the carbon on the resistor board. Search the archives for additional threads about this issue, it's a common issue.

 

[XLVII]

Hi. Does the left channel exhibit same tendencies when using headphone jack? Assuming you tried spritz of deoxit (f5). More details such as: issue occurs regardless of source; tried with batteries, etc.

 

[XLVII]

Looks like you got your answer. I'm always searching Ebay and have (2) of each model boombox in collection. Quite often this is the only way to acquire parts. Good Luck.

 

[Tinkererman]

Thanks much Superduper, and XLVII,

I'll have it apart soon, I'm going through some health issues and have some tests this week.

Slider feels prefect, no grinding, nothing - so I won't mess with it until it's off the board and apart.

Never had one that exhibited that exact problem, Rich