[Arran]

A tri sodium phosphate mix with hot water works well for cleaning a chassis, about a tablespoon in a gallon of water should do it unless it's really grungy then you may need to make a stronger mix. I pull all of the tubes out, and remove the dial if there is one attached, then pour the mixture over the chassis, then scrub around with a toothbrush. Then I leave it for about five minutes, scrubs some more, then rinse with clean hot water at least twice. If it's still grungy I go over it again with the TSP bath, then rise again. I don't immerse the chassis It's more like giving it a shower rather then a bath.
I know this goes against what people think about water and electricity but I do this on a hot day then let it dry for at least several days afterward before trying to power it up. If I have to do it on a cold day, like in the winter, I leave it in a warm dry place with lots of air circulation like near a heat register.
Regards
Arran