Power Tube Failure

@elliottbnewcombjr 

Thanks, that makes sense as a place to begin.  Yet I need to admit, with Bad (red);  Good (green) my 'Geeky' side dies just a little bit ;-).

That said, I will try to get an instruction manual with whatever tester I purchase.

Best

Since '81 I've had a few tubes go out on my entry level CJ amp & preamp.

Usually a fuse blows at the same time, with no fireworks, but I've also had a sparkler show at least once. Loud "blam" occasionally.

My K-horns are so revealing that I replace tubes when the wind noise "whoosh" gets too noticeable.

Guitar amps have been tube-driven from the beginning, so an amp shop is a great resource to test tubes.

Good luck!

About the tube testers out there for sale. If the tester measures mutual conductance it is a better one and provides a lot of useful data. If it is not a mutual conductance tester it’ll usually only tell you good, bad , shorted ,not shorted. Mutual conductance testers give you a couple of readings in the chart for new values and minimum values. So you’ll know how close to new it’s available electron supply is , how new it’s performing . 

@inagroove 

@brownred6 

"I’ve been told by tube experts most tube testers can not match tubes. They do not supply actual high DC voltage needed to the plate of the tube and thus can not measure actual plate current."

The above statement is absolutely true. I've been told by a very reputable tech that is working on a piece of equipment I have who said exactly the same thing and pointed at a tube tester under his workbench and said he may have only used it five times in the last several decades. I believe he prefers to test his tubes in circuit.