Seriously after 50 years I've never damaged a valve by pushing the heater for thirty seconds.sometimes to oops voltages! It is also the only way to ensure it gets the ''kick up the pants''. In fact with some really dead tubes I've pushed the heater to four or five times max to where it is like a brightt bulb.. And those valves are still running... If it's gonna go it will go, but it doesn't seem to weaken the heater, or shorten life as far as I see. The cathode itself is not doing its 'thermionic' thing, and the only way to guarantee emission seems to be heat. Can't oxidise in a tight vacuum, maybe the getter or the surface of the cathode material itself has some ageing effect? it is a mystery still i think . Love your tester..Subscribed, how did I miss you?
Thanks! Honestly, in this instant I was more worried about the meter of my tube tester than I was about the tube itself. I don't know how long exactly it was totally pegged, but I'm glad it didn't got damaged. Thanks for subscribing!
That's something I never knew before but your theory makes perfect sense. Might be a way to do this without a tube tester as well. Maybe a circuit with variable voltages for all the connections would have the same effect if you simply warm up the tube then give it some 5 minute bursts of over voltages in the right places.
Sure, that might work. Just pay attention that you don't go to high with the filament voltage. This article has more information on that: www.6v6.co.uk/vcomp/tech_tips/rejuvenation_tubes.htm
In a real circuit almost always this process happens automatically, usually because there is a large resistor connecting the anode to B+ and probably some cathode resistor too. What happens is that if B+ is 250V for instance, the voltage drop is less when the tube is not "woken up" and instead 150V on the anode you get 230V initially. On the cathode side the situation is the same, resulting in lower grid voltage. The first few minutes the tube might operate inadequately, but then the waking up happens and the tube behaves like a new one. By the way, I have never actually had such issue with numerous NOS tubes, even 50+ years old.
Thanks for this explanation. I have only encountered this with EC92 tubes so far. All other NOS tubes that I own test fine from the first try on my tube tester. I agree that this recovery process will happen naturally in a normal circuit, but the 2 Telefunken ones that I got here (which tested at 1 mA instead of 10 mA) were quite extreme. Depending on the circuit I do think that might take a while to correct itself. And if you are not aware of that, you might dismiss a perfectly good tube as defective and throw it in the bin. That's why I wanted to share this video. Thanks again for your feedback!
you dont even need to have B+ when you rejuvenate a tube, just set filiment voltage 10% higher for a night. it will fix it self. The principle is that it will peel off the deposits on the cathode surface.
Interesting finding that the tubes needed to be woken up. I've learnt something new! Thank you.
Thanks! Rest assured, I also still have a lot to learn in this field... Glad you enjoyed the video!
Seriously after 50 years I've never damaged a valve by pushing the heater for thirty seconds.sometimes to oops voltages! It is also the only way to ensure it gets the ''kick up the pants''. In fact with some really dead tubes I've pushed the heater to four or five times max to where it is like a brightt bulb.. And those valves are still running... If it's gonna go it will go, but it doesn't seem to weaken the heater, or shorten life as far as I see. The cathode itself is not doing its 'thermionic' thing, and the only way to guarantee emission seems to be heat. Can't oxidise in a tight vacuum, maybe the getter or the surface of the cathode material itself has some ageing effect? it is a mystery still i think
. Love your tester..Subscribed, how did I miss you?
Thanks!
Honestly, in this instant I was more worried about the meter of my tube tester than I was about the tube itself. I don't know how long exactly it was totally pegged, but I'm glad it didn't got damaged.
Thanks for subscribing!
That's something I never knew before but your theory makes perfect sense.
Might be a way to do this without a tube tester as well. Maybe a circuit with variable voltages for all the connections would have the same effect if you simply warm up the tube then give it some 5 minute bursts of over voltages in the right places.
Sure, that might work. Just pay attention that you don't go to high with the filament voltage. This article has more information on that: www.6v6.co.uk/vcomp/tech_tips/rejuvenation_tubes.htm
In a real circuit almost always this process happens automatically, usually because there is a large resistor connecting the anode to B+ and probably some cathode resistor too. What happens is that if B+ is 250V for instance, the voltage drop is less when the tube is not "woken up" and instead 150V on the anode you get 230V initially. On the cathode side the situation is the same, resulting in lower grid voltage. The first few minutes the tube might operate inadequately, but then the waking up happens and the tube behaves like a new one.
By the way, I have never actually had such issue with numerous NOS tubes, even 50+ years old.
Thanks for this explanation.
I have only encountered this with EC92 tubes so far. All other NOS tubes that I own test fine from the first try on my tube tester.
I agree that this recovery process will happen naturally in a normal circuit, but the 2 Telefunken ones that I got here (which tested at 1 mA instead of 10 mA) were quite extreme. Depending on the circuit I do think that might take a while to correct itself.
And if you are not aware of that, you might dismiss a perfectly good tube as defective and throw it in the bin. That's why I wanted to share this video.
Thanks again for your feedback!
What kind of tester do you have?
I've never seen one that you could adjust the plate voltage like that
It's a Metrix 310BTR.
Super, thank you
Thanks!
Un beau lampemetre pour contrôler les lampes triode pentode ect !! Voilà voilà merci
Merci!
you dont even need to have B+ when you rejuvenate a tube, just set filiment voltage 10% higher for a night. it will fix it self. The principle is that it will peel off the deposits on the cathode surface.
True. But I just wanted to try this without pushing the tube outside its specified maximum ratings.