Ever hear of a "smoke plate" ?

[tvcabinetblues]

Repairing an old Technics SAR330 stereo. The volume control assembly has a thin, extremely delicate, graphite/carbon colored, film sandwiched within the plastic volume knobs and is referred to as a "smoke plate" in the service manual.

What is this "smoke plate"

When I took the volume controls apart to service the mechanism, the "smoke plate" shattered, probably due to age.

I would like to try and replace it. Problem is, I don't know what the technical name for this material is, what it's actual function is (blocking light?), or whether its something that is even still available.

This "smoke plate" doesn't affect stereo operation, I technically don't need it, however it bugs me that I can't figure this out. I repaired everything but this.

Manufacturer was no help.

Any thoughts?

Thanks




[mod note: image resized for forum]

 

[Bluejets]

Is it an insulator between the volume control terminals and the mains switch terminals?

Looks like bakelite or fibre.

 

[tvcabinetblues]

When the volume is turned either up or down, a mini light bar indicator, situated around the exterior of the volume knob, increases or decreases indicating volume level. The light bar is powered by 3 mini incandescent light bulbs housed within the assembly. I'm thinking this film may help block excess light or maybe heat, from the lamps. I don't believe the film has any electrical properties. You can see the volume indicator lights below.

 

[hevans1944]

There is link to download a PDF copy of the service manual available here. You have to register on the site to download it, but that's not a big deal. The manual lists part numbers for the plastic parts in question, but they may no longer be available from the original equipment manufacturer.

This appears to be a very high quality Japanese receiver. Too bad they don't make 'em like this anymore at affordable prices. The volume control has a remote-controlled motor drive, so the light-bar is a useful feature. If you can't order a replacement you might be able to reproduce the broken one with large-format photographic film of the type used to expose the photo-resist on etched circuit boards. There are companies that will take your artwork and create the photo transparency for a small fee if you don't happen to have the photographic facilities in your home.