Hi, I purchased lots of IERC collers and use them on many toobz, even EL34s. I would thank M. Perkins who brought these notes about IERC tests ... IMHO, those guys knew their job, and the B52s era needed a stratospheric security level for those planes... as during the WWII the 813 tubes went to market :
At these times, pressurization of planes was not mandatory but cooling transmitting toobz needed to be improved . The 813 is given for a very low max PlatePwr at sea level , but FOR 10000 feet altitude ? Imagine the problem at 30000 feet ... IERC coolers are the only way to exhaust IR radiation .
At these times, pressurization of planes was not mandatory but cooling transmitting toobz needed to be improved . The 813 is given for a very low max PlatePwr at sea level , but FOR 10000 feet altitude ? Imagine the problem at 30000 feet ... IERC coolers are the only way to exhaust IR radiation .
Some info here that backs up the IERC coolers, with refs to GE and Mil Specs if one could find them it would be interesting to see what the original data said.
KH6GRT
Well, that was easier than I thought:
http://www.dscc.dla.mil/Programs/MilSpec/ListDocs.asp?BasicDoc=MIL-DTL-24251
KH6GRT
Well, that was easier than I thought:
http://www.dscc.dla.mil/Programs/MilSpec/ListDocs.asp?BasicDoc=MIL-DTL-24251
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Some more discussion on valve cooling is in the book by Kraus & Bar-Cohen titled Thermal Analysis & Control of Electronic Equipment.
http://dalmura.com.au/projects/Cooling.pdf
One aspect to appreciate is the fourth power of temperature in the Stefan-Boltzmann radiation transfer expression. To illustrate the influence, if the original plate temp was 400C and the glass 200C, and then the glass cooling improved to achieve a lower temp of 150C (and nothing else changed), the temperature of the anode would reduce to only about 393C. This may not be a great set of temperatures to illustrate what occurs with a power valve, and is based on no other changes and blackbody radiation, but somewhat dampens the enthusiasm with respect to achieving a substantial reduction in anode temperature from better glass cooling.
Ciao, Tim
http://dalmura.com.au/projects/Cooling.pdf
One aspect to appreciate is the fourth power of temperature in the Stefan-Boltzmann radiation transfer expression. To illustrate the influence, if the original plate temp was 400C and the glass 200C, and then the glass cooling improved to achieve a lower temp of 150C (and nothing else changed), the temperature of the anode would reduce to only about 393C. This may not be a great set of temperatures to illustrate what occurs with a power valve, and is based on no other changes and blackbody radiation, but somewhat dampens the enthusiasm with respect to achieving a substantial reduction in anode temperature from better glass cooling.
Ciao, Tim
More interesting are the conclusions that modest decreases in envelope temperature produce substantional increases in tube life.
I have lately updated the PEARL Tube Cooler literature to some 85 pages by the inclusion of an original work by John McAdam of International Electronic Research, the company that did the orignal research on the benefits of tube cooling, received several patents for their work and sold tens of millions of parts to the US military and the aeronautics industry over a period of some 45 years.
The relevant link is here PEARL's Products & Services
The relevant link is here PEARL's Products & Services
Sacrificial getter function is a result of short-term induction heating to a high temperature.
Continuously acting getters are usually attached to a hot running anode whose operating temperature, referring to an earlier post here, is only remotely a function of envelope temperature.
Even so, such getters are almost never used in receiving tubes with an early version of the St. Petersburg, Ru, Svetlana Winged 'C' 6550x, some implementaions of the Ei KT90 and the PEARL RB300-3CX radial beam metal-ceramic triode being notable exceptions.
Notable as well is the fact that we, PEARL, had a hand in the design of all those parts.
See this link http://www.pearl-hifi.com/06_Lit_Archive/07_Misc_Downloads/RB300_3CX_Data_Sheet.pdf for more info on the RB300
Continuously acting getters are usually attached to a hot running anode whose operating temperature, referring to an earlier post here, is only remotely a function of envelope temperature.
Even so, such getters are almost never used in receiving tubes with an early version of the St. Petersburg, Ru, Svetlana Winged 'C' 6550x, some implementaions of the Ei KT90 and the PEARL RB300-3CX radial beam metal-ceramic triode being notable exceptions.
Notable as well is the fact that we, PEARL, had a hand in the design of all those parts.
See this link http://www.pearl-hifi.com/06_Lit_Archive/07_Misc_Downloads/RB300_3CX_Data_Sheet.pdf for more info on the RB300
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I used Pearl coolers on my Fisher 50As with great success. Mother of Pearl has done his research. His website is a font of knowledge. I would be using his coolers on my new amps (and may stll) but I now have 24 tubes to cool.
Well John, have a look at the quantity pricing you can see here PEARL Tube Coolers, cowboy up, kill the heat and start getting paid by stopping spending on replacement costs for two dozen probably hot running tubes.
Spoken from the wilds of the Western Canadian North where Hank and Merle and Willie loom large . . . 🙂
Spoken from the wilds of the Western Canadian North where Hank and Merle and Willie loom large . . . 🙂
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Yes. You are right. There is vacuum inside vacuum tubes. Even if you can run the tubes inverted submerged a chilled water bath all you'd cool is the glass envelope. There is no easy way to cool the working elements of the tube by conduction.
The most practical thing you can do is run a small fan so that cool air gets inside the cabinet. But then, many amateur builders don't bother with cabinets and leave the bare chassis and glass tubes exposed. If so a fan would not help much
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One way to make this more intuitive is to realize that you need to work in absolute temperature (tubes don't care that the C scale is based on freezing point of water) But when we work in Kelvins it seems more reasonable: Given a 673K plate the glass is 473K, cooling the glass to 423K has little effect. In kelvins this seems reasonable because moving from 200C to 150C is only on order of a 10% reduction in temperature.
Our perception is biased because we use a temperature scale based on water with zero point that is at 273C above absolute zero.
The point you are missing here is that as soft glass heats up it gets "porous," allowing thereby the ingress of atmosphere and all that it contains. THIS KILLS TUBE LIFE as many years and millions upon millions of dollars of research conclusively demonstrated.
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Chris, lowering the temperature of the glass envelope would assist cooling the anode - you seem to infer it wouldn't in your first post?
I've seen some pretty bad free-air cooling setups, including 4x EL34 in a tight square sandwiched between PT and OT, and in heads with no significant fresh air path and clearly observable heat stress on the cieling of the cab. Cooling big tubes is a significant issue, but the cooling design failings are usually not helped or assisted by any 'tube-cooler' type product - and are more a result of poor total system design. I have also used small PC fans to augment air circulation in the nether regions of poorly designed heads - and agree it can be a very practical help to reduce stress on the internals.
I'm lucky enough to appreciate what Kelvin are, but I think many would not understand it, and find it harder to interpret than trying to work out what celsius levels mean (outside of 0-100) when they are used to farenheit.
Ciao, Tim
I've seen some pretty bad free-air cooling setups, including 4x EL34 in a tight square sandwiched between PT and OT, and in heads with no significant fresh air path and clearly observable heat stress on the cieling of the cab. Cooling big tubes is a significant issue, but the cooling design failings are usually not helped or assisted by any 'tube-cooler' type product - and are more a result of poor total system design. I have also used small PC fans to augment air circulation in the nether regions of poorly designed heads - and agree it can be a very practical help to reduce stress on the internals.
I'm lucky enough to appreciate what Kelvin are, but I think many would not understand it, and find it harder to interpret than trying to work out what celsius levels mean (outside of 0-100) when they are used to farenheit.
Ciao, Tim
Bill, I'm having a hard timedownloading the 85pg article, but I do recall a few significant tests on valve life back in the 50's and life was extremely long for smaller tubes, and would doubt that anyone would notice any life increase for smaller preamp/PI valves from using coolers per se, as the glass temperature is hugely lower than for big bottles.
Ciao, Tim
Ciao, Tim
Tim: go here http://www.pearl-hifi.com/03_Prod_Serv/Prod_Serv.html and click on the RH link about a third of the way down the page.
Tubes like 12AX7s and others like it that can't create much glass-temperature rise aren't likely to be much helped by coolers. Others such as 5687s die in a hurry when run at any significant plate current.
Tubes like 12AX7s and others like it that can't create much glass-temperature rise aren't likely to be much helped by coolers. Others such as 5687s die in a hurry when run at any significant plate current.
So whats wrong with a 4 dollar radio shack fan? I bought 2 4" fans (one for each amp) and limited the power to them so they spin at about 1/3 their normal speed. They are quite and at the same time circulate quite a bit of air thru my amps. Do we have a before and after temp using the tube collars so I can compare to my before and after temp using my 4 dollar fan. Most rack mounted tube gear use fans....Peavey...Marshall....Dean Markley...carvin, etc. The link being posted really is not addressing the issue....tube collars at 10+ bucks a pop = how much total reduced BTU's of heat compared to 1 4" fan? Thats the issue in my mind.
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Do you have a reference for this? I've never read anything about this. One thing that might be happening is the seal in the leads as they exist the glass envelope
You can tell if the tube has leaked, the getter will turn white inside. If this happens then you know there must be a small leak but the cause is almost certainly NOT air traveling through the glass
Back to cooling. I know of some rather dangerous experiments where the power tube was run base up with the glass envelope submerged in cool water. A very crude form of water cooling. But it does work the envelops really do stay cool if to put them on a bucket of water and keep the hose on so water continuously spills over But the anode temperature is almost unaffected and the water cooled tubes can't run any more power. The reason is the vacuum inside the tube is nearly perfect insulation and not much of the heat from the glass can get across that vacuum. Tube cool be radiation. Then the radiation hits something else and heats it
Radiation is 2-way thing: from anode to environment, and from environment to anode. Gradient of temperatures matters. The cooler is environment, the better it absorbs radiation from anode. That's why blackened heatsinks around tubes work. They absorb radiated from anodes heat energy and dissipate it by convection radiating less back to anode.
I am surprised,
That no one seems to make a plug in base (perhaps 20mm high) for the 6C33C that lifts it off the Russian type socket out of the amp chassis and a cooler that deflects the heat away from the top plate...
This is a heat issue to think about...you can cook toast with these tubes.. 🙂
Regards
M. Gregg
That no one seems to make a plug in base (perhaps 20mm high) for the 6C33C that lifts it off the Russian type socket out of the amp chassis and a cooler that deflects the heat away from the top plate...
This is a heat issue to think about...you can cook toast with these tubes.. 🙂
Regards
M. Gregg