Personal attacks aside, you read datasheets according your personal intention and conception(which is understandable and usual), this is what we have in this thread so far, just personal apinions stated as facts, unless there are factory engineers posting here.
Most of them are long dead. But since they left behind detailed textbooks covering the effects of both construction and operating parameters on tube life, and sequencing of plate voltage is not even mentioned in passing (except for specialized tubes like the VR triodes I mentioned and thyratrons, where they are quite explicit), one can say that the engineers HAVE spoken.
The RCA books are particularly enlightening, and very full of details on cathode chemistry, gettering, and the actual important considerations in assuring reliability. The same engineers published circuits where the B+ is switched on instantly, and perhaps we can assume they knew what they were doing.
The RCA books are particularly enlightening, and very full of details on cathode chemistry, gettering, and the actual important considerations in assuring reliability. The same engineers published circuits where the B+ is switched on instantly, and perhaps we can assume they knew what they were doing.
I think it is disgusting that they never tell us about the bowl of water. Even RCA never mentions it in their valve handbooks.
Time for a quote,
A billion TV sets can't be wrong. 😀
I run 6C33C. B+ and heaters on no delay with choke PSU seems to help with surge. On OTL the inrush is huge with tube conducting. I run 200V and switch heaters with B+ on. I think the most important thing with this tube is to run with heaters on for some hours before applying any B+(first power up of new tubes). Why well its rumoured that the tube components expand into a running position. People have tried applying B+ to a New cold tube and had flash over without the heater warm up time This is a one off heat up with new tubes, call it burn in, expansion time or what ever you like. After that perhaps a slow increase in B+ at first test. Then its just heaters and B+ on seems to work OK.
The warm up of heaters without B+ might help with DC coupling, however the neon trick works well.
NB its a good idea to make sure that any bias supply is up before any conduction of power tubes. That's probably one place an interlock might be good.
Regards
M. Gregg
A billion TV sets can't be wrong. 😀
I run 6C33C. B+ and heaters on no delay with choke PSU seems to help with surge. On OTL the inrush is huge with tube conducting. I run 200V and switch heaters with B+ on. I think the most important thing with this tube is to run with heaters on for some hours before applying any B+(first power up of new tubes). Why well its rumoured that the tube components expand into a running position. People have tried applying B+ to a New cold tube and had flash over without the heater warm up time This is a one off heat up with new tubes, call it burn in, expansion time or what ever you like. After that perhaps a slow increase in B+ at first test. Then its just heaters and B+ on seems to work OK.
The warm up of heaters without B+ might help with DC coupling, however the neon trick works well.
NB its a good idea to make sure that any bias supply is up before any conduction of power tubes. That's probably one place an interlock might be good.
Regards
M. Gregg
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I have the 6c33 too for 10-15 years, friends of mine too. Never had a problem with them, very reliable tube. It must be reliable because it was used for the MIG 21 airplane 🙂
I only waited for 1 minute before switching the ht on (but even if i forgot never a problem)
You mean when I said:
in contradiction to the datasheets, in the Electrical Data section?
Oh wait, that was you. Never mind.
BTW, for those who want to actually learn something about this topic and tube design and construction (tubes, not tube amps!), I highly recommend RCA's "Electron Tube Design" and RCA's "Electron Tubes" volumes 1 and 2. Tomer, of course, is the classic for non-specialists who want to know about tube life. If you're a true geek like me and are fascinated by the chemistry and metallurgy, Walter Kohl is the name to look for.
I realize the other parts of your post were useful additions but these two points answered my questions very well. It's ironic that attempts to extend tube life can shorten or just outright end it.
Also good to know while working on an amp or experimenting etc. Now I turn off the heaters as well as the plate voltage if anything is going to take longer than a minute or so. Thank you for that 🙂. -Fred
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A couple of minutes of heater only during debugging won't do much harm. Tens of minutes every time you switch on or off during normal use (e.g. guitar amp standby switch or naive unnecessary power sequencing) can soon mount up.
Yes, but the recommendations are because of the "particular schematics". If you read the paragraphs about figures 1 and 2 you will see that the issue is with applying too much voltage to the grid of the amplifier tube if B+ is applied too soon. The issue is not with applying voltage to the pass tube too soon.
This is topology specific.
As usual, and it's certainly one reason for the dispute !
A cathode biased power triode has different behaviour than a fixed grid one, specially if bias if applied immediatly.
With a penthode/tetrode the screen voltage alone can be somewhat delayed simply.
If possible, design in such way you don't need to add any complication in the PSU.
I feel this is better than waiting the cathode be hot and then suddently appying B+ on a circuit where all capacitors are (temporary) equivalent to short circuits.
In an (european) car, you won't push the right pedal down to the floor for 30 seconds before releasing brutally the left one 😀
My faith and only mine !
Yves.
Yea? tell that to my Granddaughter!
I am trying to teach her to drive a stick shift truck.
Funny name ! Here we call that a gear box lever.
Automatic ones are "paymore" options 🙁
They never had a problem is too vague, you could be more precise?
How much thousand hours these 6C33 have lasted??
Thanks
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