tube testers

[David B]

Anyone use tube testers or just plunk the tubes in the amp and pray ? I dumpster dive and occasionally fleabay for tubes so I like to see if the tube is shorted, open, or gassy using a BK 700 and if a power tube it goes into a hillbilly testbed amp to measure the current and be sure it won't short out at higher voltage..

[Brian Wallace]

I'd like to have one one day to check out what I'm getting from suppliers.

[David B]

not sure if it's necessary with new ones just as long as the source is reliable with burning in, matching and weeding out the bad tubes but then again nothing wrong with checking up on those vendors

[Brian Wallace]

I think it would be nice to see how new tubes really rate.

[Hamilton]

I have a Hickok 799 that works pretty good, but these testers don't put out the higher B+ that amps do.

[David B]

Yeah I think most tube testers were geared for TV & radio equipment voltages of the time, that's why I use a testbed amp to give the power tubes a good workout at a higher voltage before putting them in something more valuable.

[David B]

Should add the benefit with this tester is not only does it match power tubes @400v you can also hook up a signal generator to see how the tubes will behave under load not just in idle like most matchers...

[BryanL]

I had problems using an AVO Valve tester on E88CCs we were using in as video amplifiers in TV cameras.They showed up as having drooping anode current. Mullard came back with the answer "the tube is meant to be operated with a cathode resistor, not a fixed bias". The resistor gives "negative feedback", as the cathode current decreases, the grid voltage decreases, raising the cathode current, which increases the grid voltage, etc, keeping the current constant.

This will apply to output tubes, too. Test it as you use it, the maker says!

( As an ex-tube maker techie, I still feel it if won't give the milliamps at DC it won'tat AC!)