Tube tester?

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

PM for more info.

@ieales ....*wry S*...

I may be alone, but I see a lot of kismet in those pics...;)

I have had tubes since 1973. So my thinking is 'long', many of you don't see it that way.

I read so many questions here from people who have no idea if a problem is something else or a tube or tubes. Asking about tube life, IOW, shooting blind.

The Fisher President II I inherited in 1973 had tubes for it's: am tuner; fm tuner. tape deck, control center; pre-amps; multiplex adapter; phono; added stereo phono preamps.

What an ordeal checking them all just before Thanksgiving each year. I stood on the platform attached to the big wall like tester in the electronics store, separate paper bags for each unit.. People waiting behind me, it took forever, my feet and back hurt, .... each year maybe need 1 or 2 new tubes, 1 weak, 1 a short, ... but it gave me confidence in the unknown!

I always came home in pain saying "I want my own tester". One day the wife picks me up at the train, she drives me to a house, sends me up to the door, a surprise tube tester for my birthday! What a woman!!!!!

I still have the wanted ad she placed in the newspaper taped inside the Accurate 157. She's passed on, it's happy memories every time I open the lid.

I'm just saying, if you get into tubes, rather than shoot blind, get an inexpensive tester, get simple confirmation: short? strength meter, bad or weak (hardly ever), good, how good, matched strength?

It is hard to believe some tubes last 10,000 hours, it is hard to have confidence they don't need to be checked/replaced sooner than needed.

If you don't have a nearby dealer with a tube tester, it might be nice to have one of your own.  Most of the currently available models test only the most commonly used tubes (particularly tubes used by musicians in guitar amps).  My local dealer uses several vintage TV-7 testers and the modern Orange tester.  I like the Orange because it is simple to use (you don't have to look up tube data to set the numerous dials and switches that have to be set on the TV-7), and it is pretty stringent in its rating.  Tubes that test quite good on the TV-7 often fail on the Orange and the Orange tends to be correct that the tube is failing.

I have an Amplitrex, which is a tester in a different league.  It tests at full power so it sort of stress tests a tube, it is simple to use (idiot-proof is a must for me), and it tests a lot of different parameters.  If you hook it up to a laptop, it will even curve trace the tube.  The big downside is that it is expensive.

The alternative to testing is to have back up tubes that you know are good and fresh.  If you swap these in and the sound is dramatically different, you know that at least some of the tubes in your currently operating set are becoming weak.  You can then do one-by-one swapping to perhaps identify the culprit; alternatively, you can just change all of the tubes at once and get a new set of reserve tubes.

I’ve been ’into’ tubes since the 1950’s w my Dad’s Bogen. I always wanted a tester. Many testers don’t actually test in operation range. I considered the µTrace, but it’s more of an engineer or amp designer than hobbyist’s tool. Hence, the tester shown above.

I have a pal that manufactures tube gear who lives a couple of blocks away. He has a Hickok which showed good on a KT88. Sonically, it clearly wasn't, so dammit, design and build one that can test in actual operation! Results below.

It can easily be modified to include 2x 9 banana plugs and as many sockets as desired to test almost any tube. In 50+ years of tube amp ownership, every tube I’ve owned can be tested in just the two sockets installed.