Last weekend I bought a 1000A and I have read a lot about the OPTs being bad so I'd like to see if mine are OK. How do I go about checking them out? Can I take the 7591s out and then test it with power or should I test it without powering up? I haven't put any power to it yet and don't want to unless it can be done safely. The seller said that it hasn't been ran in many years and it appears to be original except for the unblown 10 amp fuse that it has in it and two output tubes. The fuse is what makes me nervous. It is a Dec. 1965 build with one bias pot. I can't complete this project right now because I have so many other things going on but would just like to know if it's going to be fixable without spending a great deal of money on it.