Tube Tester

Budget?

I would only consider a mutual conductance tester. TV7 is plentiful, and probably the entry level as far as cost is concerned. Built for military use, they are very durable. From there you can go up, up, up in cost.

It does sound like you had an output tube that shorted. To check for shorts in a tube, a tube tester is not required, a multi-meter would be sufficient. Good luck with the hunt.

How to check tubes with a multimeter.

https://youtu.be/_M_lCwQgCMA?feature=shared

Agree with Viridian that you want a tester that measures transconductance. And that usually means Hickok or B&K (often made by Hickok.) Transconductance of a given tube varies with plate voltage and current. Unfortunately very few vintage testers are capable of providing adequate voltage and current for power tubes. Hence you may get a misleading reading for transconductance. Best to test power tubes in the amplifier where you can know plate V and current by direct calculation. And measure grid bias as a guide to tube wear. For big bucks you can get a modern tester that does a proper job, but IMO it’s not needed.

Searching for a bad tube is pretty easy. I always have a spare set. You just substitute one at a time until you find the bad tube... or eliminate the problem from being a tube. Most companies that supply matched tubes write down their electrical test results on the box or tube, so you can order a single tube matched replacement. 

take a chance, buy a tester, test new tubes you buy, test periodically, find problems, importantly rule tubes out when problems occur

https://www.ebay.com/itm/267254977386?mkevt=1&mkcid=1&mkrid=711-53200-19255-0&campid=5338381866&toolid=10001&customid=077df128-34b8-11f0-918f-313438613262

get this too

https://vacuumtubesinc.com/index.php/books/the-jackson-model-648-manual.html

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Recently purchased a BK Dyna Jet 707 tube tester on Ebay.

Sent it off to another 

Ebay gentlemen that refurbish and calibrated it. All in less than $350.

Works great. 

If you must buy a tube tester first learn about the features and capabilities of all the various Hickok testers. Then buy the best you can afford that has been refurbished, calibrated, and guaranteed by the seller. And keep in mind that most cannot properly test a power tube. For small signal tubes, they’re fine. I stipulate Hickok because they were the premier company and are still revered. Hence there are guys who can repair them, and parts are available. Also, they were simply the best. So far as I can tell, Hickok made the BK testers too. That’s if you’re going to buy vintage. If you want to spend big bucks and buy new, see Amplitron and others.

It is a bit more $$ but I am a big fan of the µ-tracer.

https://www.dos4ever.com/uTracer3/uTracer3_pag0.html

dave

What Dave said. Also, it’s “Amplitrex”, not Amplitron.

I've had several tube testers and they all worked pretty well. But they all work and test differently. My problem was that most testers didn't test all of the tube types I was using. I finally settled on a Heathkit TT-1A, based on (but not the same as) the Weston 981-3. I can test just about any tube ever made. Mine was a factory build but many of the home builds are just fine. Like any analog tube tester it pays to either buy a unit that was recently serviced or get it serviced. That makes all the difference and provides confidence and assurance in the test values.

Like I said, most vintage testers cannot deliver either enough plate voltage or plate current or both to properly test power tubes, and also a few high transconductance 9 pin miniature small signal tubes. So you will get a result but it may not represent what the tube actually does in your circuit. Ergo, it may be better to test a power tube in the amplifier circuit. There are exceptions of course. As tubes age, the grid bias voltage, which must be negative with respect to the cathode, drifts “up” from negative toward zero in order to pass the desired current. That’s “transcenductance”. So tubes that are trending toward zero difference from the cathode V over time are wearing out. That’s how tubes die.

Thanks everyone for all the comments thus far. They are extremely helpful in doing my research.  I’m still very much in the absorbing and learning mode. All your perspectives are very helpful. 
 

One quick response though. I can’t go and swap out one on one to find the bad tube. I tried it once and cause major repairs with my “circuit” board. Essentially the turning off and on with bad tubes fried some transistors or some other electronics. Expensive mistake.

thanks again 

You CAN do that if you do it properly. To be certain that no damage will occur, unplug the amplifier before swapping tubes.  I don't know exactly what went wrong in your case, but maybe you swapped tubes with power on. Or if you turned the amplifier off via its power switch, perhaps that amplifier had a power supply that was always powered up, even when the switch was in the off position.  That is not uncommon but is usually done so not to be a danger.  In any case, if you pull the plug, you are safe.

I bought this one from Space Tech Labs. It’s been great. Very easy to use and matches what other testers read. 
Space Tech Labs

If I had a dealership again or had to test tubes more often I would consider investing in the Space Tech Labs unit.