We explained you many times that current regulation for tube heaters to heat up slowly helps; also HT coming up slowly helps; I even put here for you schematics of both filament stabilizer and of an intelligent B+ regulator, but you even did not dare to take a look at them, but continue to pretend as if you are trying to prove that we are wrong, because you don't know what is right, and have beliefs only, and assume that we don't have a knowledge, like you, but have different beliefs...
What a mess in your understanding, Joshua!
Good luck!
No, but sudden application of HT on already hot tubes ALWAYS results in monstruous cathode peak currents before the link caps (and -worst- the large cathode bypass ones) be fully charged.
My Faith:
- ALWAYS use grid bias for power tubes applied as soon as possible.
- For penthodes, consider delaying the application of the screen voltage (easy, since screen voltage of power pentodes MUST ALWAYS be regulated)
- Unless you use IST, lo power tubes have sufficient resistance in their anodes to protect'em.
Yves.
OT personal remarks deleted. Back to the topic, gentlemen!
I've learn a lot following that post and I will probably keep some in account for next design.
I just want to add something that all engineers (should) know:
Always consider the side effetcs of protective circuits you are planning to add and insure that remedy won't be worst that disease . . . imaginary or not !
The higher the number of components, the lower the MTBF.
Ah ! and use low cost tubes, they sound as well as expensive ones . . . if not better
Yves.
I just want to add something that all engineers (should) know:
Always consider the side effetcs of protective circuits you are planning to add and insure that remedy won't be worst that disease . . . imaginary or not !
The higher the number of components, the lower the MTBF.
Ah ! and use low cost tubes, they sound as well as expensive ones . . . if not better
Yves.
No, it does not do very same thing.
My stabilizer waits for the tubes to start to draw current, then (after that!) slowly comes on the regime. It was designed by Engineer. That's the point. Yours is just a delayed rectifier designed by a hobbyist that delays B+ application according to your understanding of right time delay. If your solution satisfies you better, it is your right. Why I put mine here, to show an example how it is possible to reduce stress caused by sudden B+ application on tubes.
Please don't generalize: I meant your messy reasoning.
Speaking of Tektronix, SY and myself assumed that they were good engineers, and tried to find a reasonable explanation to why they did something weird.
My stabilizer waits for the tubes to start to draw current, then (after that!) slowly comes on the regime. It was designed by Engineer. That's the point. Yours is just a delayed rectifier designed by a hobbyist that delays B+ application according to your understanding of right time delay. If your solution satisfies you better, it is your right. Why I put mine here, to show an example how it is possible to reduce stress caused by sudden B+ application on tubes.
Please don't generalize: I meant your messy reasoning.
Speaking of Tektronix, SY and myself assumed that they were good engineers, and tried to find a reasonable explanation to why they did something weird.
Once more, the last attempt to explain: the point is it is a stabilizer that waits for tubes to start drawing the current
Do you hear me now?
Once more, slowly, spelling each letter: stabilizer, not just a time delayed rectifier. It does not delay time. Instead, it senses current, and speed of voltage increase depends on current. Such a way I minimize grid currents in stages caused by charging interstage and cathode bypass capacitors, and minimize cathode currents caused by such stressful charges of capacitors.
I am over.
Good luck!
It is normal. I don't expect everyone to go through 23 pages thoroughly trying to understand all points of view. That's why I want to stress once more that sudden delayed B+ application on already hot tubes is more harmful than unproven benefit of absence of B+ on cold tubes. Why it is harmful, because of interstage capacitors that have to be charged through grid currents. It is harmful especially for output tubes in Push-Pull amps, and even more harmful if they have cathode bias with bypass capacitor. It is easy to calculate power dissipated by tubes when voltages on anodes are maximal, and currents through tubes are also maximal.
I looked at your schematics again. I fail to see how your B+ regulator is current sensing and slow coming. It looks like a conventional series regulator.
A tip: where a conventional series regulator gets a reference voltage from?
Here is it again, for your convenience:
Last edited:
The answer is: it gets it from C3, which is 2,200 uF. C3 is charged by current drawn by load. The voltage goes up until reaches limit set by a shunt regulator (Q3, D3, R3) that is 12V. So, time delay is equal to 2,200 uF multiplied by 12V divided by current. When tubes are cold an initial current that charges C3 is supplied by R1, R2, Q2 in series.
Why is it harmful? Obviously you're referring to a brief surge in cathode current, but why is that harmful?
Has anyone done any testing or know of such a test being performed to determine the effect of instant HT on a valve? To the point of examining failure modes, dismantling the electrodes for inspection and analysis. I was thinking along the lines of say 100 triodes or pentodes [same batch] each connected as a single stage amplifier. One half of the batch cycled with soft start HT, the other full HT applied before the cathode has heated up. It would be an interesting experiment!
Hi,
Sorry for popping in so late...Wavebourn knows his stuff, the alpha et omega of how a vacuum tube works.
Haven't read the rest of the pages yet but I guess it's about software upon which I'll only say that the old IBM office stuff is much more intuitive and logical than anything Microsoft has ever come up with....Just my opinion.
As MJ would say, crickey...
Cheers ,
Congratulations!
One more woke up from propaganda-induced dreams.
If you examine datasheets carefully they specify max voltages for hot tubes, for cut-off tubes with high negative bias, and for cold tubes. Max voltage for cold tubes is the highest one. It is given bor the case when the equipment is switched on, and rectified voltage is on it's maximum because no current is drawn yet by cold tubes.
Sorry for popping in so late...Wavebourn knows his stuff, the alpha et omega of how a vacuum tube works.
Haven't read the rest of the pages yet but I guess it's about software upon which I'll only say that the old IBM office stuff is much more intuitive and logical than anything Microsoft has ever come up with....Just my opinion.
As MJ would say, crickey...
Cheers ,
Hi,
Maybe you should reread the gentleman's article from the correct perspective.
He's talking about CRT tubes which was his field of expertise at Philips.
Delaying B+ is not bad practice (even though it's unecessary in most situations) in fact it's sometimes needed to avoid popping grids or to warm cathodes of particularly slow beasts such as 6336A's and family.
Either way, cathode stripping will definitely occur when a proportionally too big signal is applied with respect to the state of warm up of the cathode.
No signal, no cathode stripping.
Doesn't matter if B+ is applied before or after the heater voltage or simultaneously, the tube should ready to go ( i.e. properly warmed up) before it's put to work.
This is stuff that's been talked about before here and should be one of the first things you should understand about tubes before you touch them, not after.
And no, like most other things in life, nothing's ever truly black or white....
Cheers,
Maybe you should reread the gentleman's article from the correct perspective.
He's talking about CRT tubes which was his field of expertise at Philips.
Delaying B+ is not bad practice (even though it's unecessary in most situations) in fact it's sometimes needed to avoid popping grids or to warm cathodes of particularly slow beasts such as 6336A's and family.
Either way, cathode stripping will definitely occur when a proportionally too big signal is applied with respect to the state of warm up of the cathode.
No signal, no cathode stripping.
Doesn't matter if B+ is applied before or after the heater voltage or simultaneously, the tube should ready to go ( i.e. properly warmed up) before it's put to work.
This is stuff that's been talked about before here and should be one of the first things you should understand about tubes before you touch them, not after.
And no, like most other things in life, nothing's ever truly black or white....
Cheers,
Why?
For the beginning, because a tube manufacturer would not accept your complain if finds out that you exploit tubes out of specs, even shortly.
I ordered tubes from eBay which arrived today. The eBay listing said 6CJ3/6DW4B and the tubes I received are 6DW4B. Are they as good for this purpose as 6CJ3? On the datasheets there are some differences between the two.
Hi,
Maybe you should reread the gentleman's article from the correct perspective.
He's talking about CRT tubes which was his field of expertise at Philips.
Delaying B+ is not bad practice (even though it's unecessary in most situations) in fact it's sometimes needed to avoid popping grids or to warm cathodes of particularly slow beasts such as 6336A's and family.
Either way, cathode stripping will definitely occur when a proportionally too big signal is applied with respect to the state of warm up of the cathode.
No signal, no cathode stripping.
Doesn't matter if B+ is applied before or after the heater voltage or simultaneously, the tube should ready to go ( i.e. properly warmed up) before it's put to work.
This is stuff that's been talked about before here and should be one of the first things you should understand about tubes before you touch them, not after.
And no, like most other things in life, nothing's ever truly black or white....
Cheers,
No, I think you need to reread the whole shebang. This is not a thread about IBM, Microsoft, or cathode ray tubes.
It's about B+ on cold cathodes in indirectly heated tubes.
Oh, and wether someone knows or believes a cathode should be hot, or is ok cold, has nothing to do about how he designs and builds tube circuits. It's only of interest in regards of the tube's life.
I know all there is to know about tubes, have been for ten years, still I learn something new all the time. Next year I'm sure I'll wonder over all the things I know that I didn't just a year prior...just like you
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