Same is true of vintage 45's and 2A3's. They have 2.5 volt filaments.

And none of the above have indirect cathodes which complicates the process further, in case you were thinking about making some kind of converter to use a pentode such as the 6L6 or 807 (now there's a neat one) wired as a triode. But it can be done.

So find out what you need, and be patient. In the end, all is possible.

And the Chinese, particularly Shuguang, are turning out very good tubes. I have no connection with them other than buying a few now and then.

:::Hello! I am very excited.I am aquiring a Sparton highboy that I am 99% sure is a 301 equasonne.(not the really huge one).I don't know what power tubes it has yet but they could be 50's.I hope so because that would be really cool,I love huge tubes and you can still get them and there are some new Chinese built ones.The craftmanship on the radio is gorgeous and there are doors that open to expose the radio.Anyways what is with the #50 and#10 power tubes being so rare ?Were these only made for Sparton radios?I see that the 50's can handle something like 600 plate volts.Why were these discontinued? One more thing,if the power tubes are 182's or 183's can these be substituted with 71A's?Does anyone here own one of these radios?
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:::IPAddress: ***.12.191.237
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::I have a Sparton Equasonne, not sure of model number. The one I have has three chassis assemblies. The set came with Cardon (brand name) 285 tubes; the sockets are marked 285/250; a 1937 Sylvania tube manual lists the 50 as a substitute for 285. Other tubes are Cardon 484 or 483 (I do not remember). The Equasonne has a unique circuit. Although some later sets used another tube, the set I have has the antenna feeding a tuner assembly consisting of a four gang variable condenser and four coils - no tubes or other components. After this 'tuner', there are five stages of untuned RF amplication, and a detector. Beautiful solid walnut cabinet, wood dors over the radio, some hand-painted detail, and a significant amount of carved wood (not repwood). The 250 (50)tube was used briefly in other sets, such as some Grundig-Majestic and other high-end sets. Hams used it, which may explain why there are not many floating around. The 250 (50) was short-lived, as the (2)42, (2)47, and later the 6L6 soon became the tube of choice for high output audio. The 250 / 50 is a triode which can run at high plate voltage, and it is pretty finicky, and has a short life span before the filament loses emmissability. Transformer input coupling must be employed, and the tube is easily ruined - disconnecting the speaker, etc. Some Sparton Equasonne used 183 or 182 tubes; do not substitute with a 71A. And do not replace a 384 with a 27; I have seen it done - wrong filament voltage.
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:Correction - that should be Cardon 585, not 285 and 484. EdM
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::IPAddress: ***.112.18.238
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:IPAddress: ***.112.18.238

IPAddress: ***.188.127.197