Hi,I realize that your post is very old.About 14 years old.But in replying,IMHO,instead of wasting so many hours trying to repair the 604S,or any VSX receiver,Isn't it more logical to simply set it aside and buy another good used one on ebay at a steal of a deal kind of auction?And keep the fixer upper one for parts.These come a dime a dozen now days and they are so old.If you really want a great receiver,look for the silver faced Pioneers from the mid 70's to 1980.But you guys already know that.
The VSX line of receivers are very good,they have to be to carry the Pioneer logo.But economically speaking,it's not worth the cost to repair them,just go buy another one since they are so plentiful on the internet.But,it's just my opinion from one Vietnam Veteran to another,brother.
On the other hand,if it's a very minor repair like a blown fuse or a relay,etc,then surely go ahead and repair it.This is my first post on audioholics.Have a great week everyone.