I had the VR4JR for a while, but never had a problem with the adjustment of the ambiance tweeter. Have you pulled the plate/assembly out to confirm that its still wired? have you lost control or all sound out of the tweeter?
finally, is it possible that the dial has lost its grip on the pole and while you are turning the dial, it is not turning the pole/shaft?
finally, is it possible that the dial has lost its grip on the pole and while you are turning the dial, it is not turning the pole/shaft?