Old brittle insulation on circuitry is vibrating/buzzing. Easy solutions?

[eschertron]

You don't want a 'grommet', you want one of these (by any supplier) Original-Strain-Relief-Round

If you have a grommet, or get one from the local hardware store (noting the strain relief is preferred, and also likely available at the store), then put a knot in the power cord inside the chassis to act as slip prevention.

[Triocd]

Yes, Thank you! : )

[eschertron]

I've had no problem sourcing stuff like strain reliefs, grommets, etc., from local hardware stores - Mom & Pop, and up to the big boxes seem to have a decent selection - so it's my assumption that with a few well-placed technical descriptions that you will find exactly what you need near at hand. Of course, this assumes you live closer to 'middle america' than 'middle earth'.