Testing Tubes

I recently found an old 1960s era tube amp that my grandfather built, and I hooked it up to a speaker I had laying around to see if it worked. Lo and behold, the thing worked! Unfortunately, there was a massive hissing sound coming through from somewhere.

So, I opened it up and first thing I noticed was a pair of capacitors had exploded. I ordered the equivalent from parts-express, and am currently waiting for them to arrive. I am hoping that the new caps fix the problem.
However, I would also like to know if there is a way to test the tubes as well, just in case they are the cause.

Thanks! :)

JimJ would be your man for this question, he knows a good bit about such.

As you found out, electrolytic caps are usually the first things to go from something of that age.

A good tube tester is not a cheap piece of gear, so I wouldn't really bother with trying to test the ones you have.

Do you have a pic of the amp? If you don't have a use for it, I might :D