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Old 19th February 2021, 06:15 AM   #1
mooreamps is offline mooreamps  United States
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Default Data Sheets

I am wondering, who would it be, for me to talk to, to update some of these spec's in tube data sheets...?
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Old 19th February 2021, 06:43 AM   #2
Diabolical Artificer is offline Diabolical Artificer  United Kingdom
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What specs what valves? Are you talking about a Mullard Exxx type of thing? The problem is most valve manufacturers have long since disappeared, also unless your talking about obscure valves or triode curves typa thing most datasheets are pretty comprehensive.


Andy.
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Old 19th February 2021, 02:32 PM   #3
mooreamps is offline mooreamps  United States
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Default EZ-81

I want to update the spec on the EZ-81.
Change the max input cap from 40 uF, to 100 uF.
Just for a start.....
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Old 19th February 2021, 02:35 PM   #4
mooreamps is offline mooreamps  United States
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Quote:
Originally Posted by Diabolical Artificer View Post
datasheets are pretty comprehensive.
Andy.
Most tube data sheets strike me as like the pirates' code "they just guidelines".
I see most people treat these tube data sheets as if a tube were a solid state device, and they are not........
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Old 19th February 2021, 03:50 PM   #5
v4lve lover is offline v4lve lover  Netherlands
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Quote:
Originally Posted by mooreamps View Post
I want to update the spec on the EZ-81.
Change the max input cap from 40 uF, to 100 uF.
Just for a start.....

You could put an alternative data-sheet in circulation that shows operating conditions with higher capacitance, but you would also have to up the minimum series resistance requirement to keep it within permissible current spikes. But then again, most designers of tube equipment don't read data-sheets Otherwise rectifiers would last forever and that cuts into their margins.



The flip-side of the coin is that these permissible maximums are there for a reason, and 40uF is too much considering modern SMPS optimized electrolytics are harder on the tube anyway cause of lower ESL and ESR.


Whats the point in putting 100uF and overloading the tube during the start up? In push pull most of the ripple is cancelled in the OPT anyway.
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Old 19th February 2021, 04:24 PM   #6
jhstewart9 is offline jhstewart9  Canada
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Default frank.pocnet.net/

One of the best data sheet resources.
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Old 19th February 2021, 08:54 PM   #7
mooreamps is offline mooreamps  United States
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Originally Posted by v4lve lover View Post
You could put an alternative data-sheet in circulation that shows operating conditions with higher capacitance, but you would also have to up the minimum series resistance requirement to keep it within permissible current spikes. But then again, most designers of tube equipment don't read data-sheets Otherwise rectifiers would last forever and that cuts into their margins.



The flip-side of the coin is that these permissible maximums are there for a reason, and 40uF is too much considering modern SMPS optimized electrolytics are harder on the tube anyway cause of lower ESL and ESR.


Whats the point in putting 100uF and overloading the tube during the start up? In push pull most of the ripple is cancelled in the OPT anyway.
You are joking ?

1. designers follow the spec like it come down from the hand of God.
2. the reason, when this spec was first published, the biggest paper cap , in them days, was about's in the 40 uF range. The electrolytes did not appear until the late 1950's.
3. push-pull has nothing to do with it.
4. It takes the EZ-81 about 10 seconds to warm up, and you saying "current spikes" and lower Effective Series Resistance ?
5. one point being ; inside surface amplifier ; it uses a dual 100uf cap with 10 henry choke ; as a pi filter for the B+. Just using what parts that could be had for a plate supply......

Last edited by mooreamps; 19th February 2021 at 08:58 PM. Reason: addded content
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Old 19th February 2021, 09:13 PM   #8
v4lve lover is offline v4lve lover  Netherlands
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Default Somtimes..

Quote:
Originally Posted by mooreamps View Post
You are joking ?

1. designers follow the spec like it come down from the hand of God.
2. the reason, when this spec was first published, the biggest paper cap , in them days, was about's in the 40 uF range. The electrolytes did not appear until the late 1950's.
3. push-pull has nothing to do with it.
4. It takes the EZ-81 about 10 seconds to warm up, and you saying "current spikes" and lower Effective Series Resistance ?
5. one point being ; inside surface amplifier ; it uses a dual 100uf cap with 10 henry choke ; as a pi filter for the B+. Just using what parts that could be had for a plate supply......



1. Those specs are there for a reason, just because it doesn't blow up on the spot doesn't mean ignoring the design specifications is sound engineering. I just Simulated the EZ81 in PSUD2 and increasing C1 in size from 40 to 100u does have the effect of increasing the number of mains cycles the cathode is required to provide excessive current.


2. I have prewar (1939) Radios in my collection that have paper aluminium electrlytic capacitors in them filled with Boric Acid. Nasty stuff to replace. Your timetable is off by a couple decades. Here in the Netherlands they are called "mushroom capacitors" by collectors due to their crimped on top. and have been in use since the early 30's il see if i can find some whit date codes.



3. Yes it does, push pull amplifiers will tolerate 10's of volts of peak to peak ripple on the electrolytic feeding the output transformer with no discernable noise on the output. For Single ended however you need a much cleaner supply.


4. Yes, if you read the data sheet you would have seen that they specify a minimum series resistance measured from the center tap to each anode of the tube. This is to limit the current through each section of the rectifier. If you violate this specification there is a good chance nothing will happen, but dont act surprised when your super special GEC 5R4GY starts arcing because you put 100 instead of 4uF before the choke and didn't bother to read up on the plate to plate series resistance.


5. I don't know that particular amp, so i really cannot comment.


Oh and to answer your original question, if the current manufacturers feel that their cathodes can withstand higher peak currents than the old production stuff im sure they would have advertised this by now, fact of the matter is that cathode formulations are more or less the same in current production runs as in NOS tubes. Just because there is not a marked nor R&D money to put something better in tubes. Currently there is no one administering or updating any old data sheets, Or any central authority like you have whit 2Nxxx transistors (JEDEC?)

If you looked at any datasheets you would have seen Philips (The parent company of mullard) stopped revising them around C 1968.

Last edited by v4lve lover; 19th February 2021 at 09:20 PM.
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Old 19th February 2021, 11:11 PM   #9
jhstewart9 is offline jhstewart9  Canada
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Quote:
Originally Posted by mooreamps View Post
I am wondering, who would it be, for me to talk to, to update some of these spec's in tube data sheets...?

I'll pass on your recommendations. How about a sample schematic of one of your amps that use parts beyond spec? What are typical MTBFs? And which parts fail first?
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Old 20th February 2021, 03:48 AM   #10
mooreamps is offline mooreamps  United States
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no parts have failed.
this is the amp.... is a prototype , built for my own personal use..
as you can see , on top of the white box , the ez-81, the 500v dual 100uf cap, and the 10 henry choke.
Surface 3 Full Build - YouTube

still does not answer my question.
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