Tube tester?

Check craigslist, they typically aren't too much money there and they almost always seem to have.  Years ago, every hardware and drugstore had one.  You'd take your tubes in a grocery bag and plug away.  I do not have one.  I listen and if something is off, I swap the whole set for said device.  If you test and find a bad one, a new one will not match up with the old ones. 

I bought a tube tester when I started playing with DHT and rectifiers.     Having one actually saved my new amp from a shorted rectifier.   It was a NOS 5r4gy from 1956 that I bought as a group of 4.  They were time capsule condition yet one was bad

Your best bet is to pay a few bucks extra to have pairs and quads matched.   Also a good idea to have dual triodes matched and screened for noise.   My best quality tube sets have been purchased from trusted sources that match.    This was proven after testing a bunch of tubes collected over the years

When I receive them I also test them. 

I was lucky, I bought a mint Hickok that works great and is accurate with several "bogey" tubes so it's more than accurate for weeding out bad tubes and matching good ones.    MOST TUBE TESTERS NEED WORK.    Always remember that if thinking of getting one.   

Almost all of my gear has tubes so for me it is peace of mind. 

It is rare to find one this nice that works so use caution if looking for one.  Best to just buy from vendors with an Amplitrex or similar computerized test equipment.  

I'm in northern New Jersey if you are local and want to swing by to test your tubes or ship them. No charge 

Very nice and helpful guys here. If you need replacements they can also help. It's best to have a spare set to plug in while the tubes being tested are away.

Build your own. I have schematic, parts list, cad dwg and PCB.

PM for more info.