Hello, the rotating dial with playback direction control knob of my DVX4 fell off last week.
I checked now with a local JVC official repair centre. Their procedure is to replace the entire circuit board on which the dial is mounted which means quite a lot of the total cost is hw related. Their quote translates to 330 US dollars...

Looking at the construction of how the rotating dial is mounted it's a miracle it has stayed in place this far. It mounts to a underlying circuit board but I can't figure out how the fastener plastic knobs can really be made to keep the dial in place. I think it will be possible to drill a very small hole in the centre plastic pin and screw a likewise small screw into it from underside the PCB to hold the button + some epoxy glue. But I have not gone into action yet.

I have figured out how I can control the camera even with the knobs not in place but it's a bit inconvenient. A small screwdriver serves a purpose in that solution.

Given the repair quote it seems better to pick up a $100 unit on Ebay that's broken in some other way and transfer the circuit board from that unit. To remove some disassembly guesswork it would ge great to find a DVX4 service manual that hint how to go about swapping the PCB. /gunnar