This is from "The Retr0bright Project".
By Merlin, of AmiBay, English Amiga Board and Vintage Computer Forums (among others)
How to deal with the “not-so-mellow yellow” of old computers and consoles
“The problem was finally cracked in late July 2008 with a mixture of hydrogen peroxide, a small amount of an “Oxy” laundry booster as a catalyst and a UV lamp; we believed that this could do the job in hours instead of days. Proof of this concept was demonstrated on EAB by Tonyyeb from Hull, UK, Chiark from Leeds, UK and myself. The original test I did as proof of concept took two hours, as opposed to up to the five days it took for the original tests at CBM and a1k.org. We were on to something!!
See the complete article at: retr0bright.wikispaces.com
Coloque as teclas em água oxigenada + bicarbonato de sódio e deixe algumas horas no sol. De preferência cubra o recipiente com um plástico.