hey guys anyone know where can i find a Marshall JCM 800 (2203) with 6650 tubes in it? is the only way of getting it through ebay or something? or can i get it brand new from some shops?
You cannot get a JCM800 with 6550 tubes brand new any more. Those were made back in the 80s when there was a shortage EL34s. All new JCM800s come with EL34s. And yes, going from EL34s to 6550s can be done but require more than a simple rebiasing.
Anyway, if TS wants a 2203 with 6550s, he should check out Ceriatone and their 2203 clone. No harm contacting Nik and asking him if he can do a one-off with 6550s instead of EL34s, just for you.