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First treat the ball with hydrochloric acid 50% in water.Keep it in the solution for 1 day.
Then use Hydrogen peroxid 100 volumes keep also one day long
Use a brush afterwards

I send to you a diagram . May be I can help you
Is in attachment
Regards Francisco Carmo

I have a new receiver to replace in the ceiling fan.

Ceiling has 3 wires : Brown (L) + Blue (neutral ) + Yellow/Green ( ground)

Receiver-IN 3 wires : Brown (L) + Blue (neutral) +...