Rotary dimmer control for 5 light chandelier stops dimming

Whoa...You definitely may have a fire and/or shock hazard hanging from your ceiling. I've seen a lot of fixtures with old, brittle wire and bad insulation in them. Lamp wiring is subjected to a lot of heat, especially with higher-wattage fixtures. Long term exposure to heat near or above the insulation's rating is especially damaging to electrical insulation. I've also seen cases where metal parts of the bulb socket partially melted and/or broke loose.

If you're comfortable and confident of your abilities to make a safe electrical connection, you can replace the wire and bulb sockets in your fixture. If it's valuable or an attractive antique, it's worth fixing or having fixed, even if you sell it. Just make sure you use wire with insulation rated for use in an electrical fixture. It must be rated for a temperature no less than 105 degrees Celsius.

It it's a lower cost fixture, replace it or have it replaced. Regardless of what you do, you're probably going to be replacing that dimmer again...sorry.

If you live in an older home, it may be worth (in terms of safety) having a few qualified electricians evaluate your electrical system as a whole to make sure everything is still in safe condition.