Yeah, I made one
I call it the VacuTrace. Took me forever to design because for some stupid reason I decided to do it entirely analog. Should have put an 8-bit micro in there to make things easier. But hey, it works very nice. Super useful for matching tubes. Exactly.
jh🙂
I call it the VacuTrace. Took me forever to design because for some stupid reason I decided to do it entirely analog. Should have put an 8-bit micro in there to make things easier. But hey, it works very nice. Super useful for matching tubes. Exactly.
jh🙂
I've once built one for a friend from Glass Audio, but don't remember which issue.
It works fine, checks for noise, distorsion, amplification.
Dick.
It works fine, checks for noise, distorsion, amplification.
Dick.
Very simple tube tester for EL34, EL84 and ECC83 (12AX7).
Some passive components and external universal meter.
You can build it just in one hour 🙂
Schematic diagram is self explanatory (I hope because description is in polish
.
Some passive components and external universal meter.
You can build it just in one hour 🙂
Schematic diagram is self explanatory (I hope because description is in polish
.
Check the tube for shorts BEFORE plugging it in to something like that. 😉
My Eico 625 just applies a current-limited supply to all electrodes except cathode and heaters, so it kinda tests emission as much as anything... will tell you if your tube is really in the pits though.
Tim
My Eico 625 just applies a current-limited supply to all electrodes except cathode and heaters, so it kinda tests emission as much as anything... will tell you if your tube is really in the pits though.
Tim
Sch3mat1c said:
Eek! The grid is closest to the cathode, so it has the most influence on the electric field and will draw most of the current, but it's not designed to dissipate power. Read what Tomer has to say about valve testers in his "Getting the most out of vacuum tubesz" book. He was in a position to know, and his conclusions about most testers are frightening.
build tester
I find lots EL84/6BQ5 old valves (arround 200 units), in the box are used and new, all mix.
I want test 1 to 1, but I dont a tube tester.; search in last topics:
Sch3mat1c say _build amp plug the tube and measure voltages and currents...Check the tube for shorts BEFORE
ok. but How I check for the tube shorts ???
Gsmok put link for simple tube tester, ok is god idea but no limits currents, how upgrade this schematics to limits currents, in plate and grid?
thanks.
alejo
I find lots EL84/6BQ5 old valves (arround 200 units), in the box are used and new, all mix.
I want test 1 to 1, but I dont a tube tester.; search in last topics:
Sch3mat1c say _build amp plug the tube and measure voltages and currents...Check the tube for shorts BEFORE
ok. but How I check for the tube shorts ???
Gsmok put link for simple tube tester, ok is god idea but no limits currents, how upgrade this schematics to limits currents, in plate and grid?
thanks.
alejo
All you really need to test an EL84 is a 300V HT supply, a heater supply, and a few components. Connect the +300V to the anode and screen grid (add a 100 Ohm 1/2W resistor in the path of the screen grid to prevent oscillation. Connect the cathode and g3 to 0V via a 270 Ohm 1W resistor. Connect the grid to 0V via a 10k resistor. Apply heater power and you should see about 11V on the cathode - indicating 41mA of current.
Shorts: The most dangerous short is between grid and cathode. But it may not show up hot. You could use a meter on its resistance range to test with heater power applied, but I wouldn't bother. I'd just pop it in the test circuit and switch off the 300V if there's a firework display in the valve or if the voltage across the 270 Ohm resistor rises beyond 15V.
Shorts: The most dangerous short is between grid and cathode. But it may not show up hot. You could use a meter on its resistance range to test with heater power applied, but I wouldn't bother. I'd just pop it in the test circuit and switch off the 300V if there's a firework display in the valve or if the voltage across the 270 Ohm resistor rises beyond 15V.
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