Trying to diagnose dead right channel in JVC RC-838jw. Pre-amp is fine, outputs signals in both channels. Bridging signal at the amp brings dead channel back to life. All signs point to defective balance slider. Tonal sliders have no effect and I suspect they are worn out. Come to think of it, the (2) M70's on my shelf also have tonal controls with minimal effect. Of course I've already cleaned them. Found one source that might have them, mega expensive. I'm reluctant to believe that the sliders are this wear prone. Never had problem with rotating controls not responding to a good cleaning.

Question: What is your experience? Are the slide controls, especially with JVC's, failure prone?