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#1
Posted to rec.audio.tubes
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What is a 4X250F?
I have a few of these I got in a box of tubes. What are they used for?
They are strange looking guys. Any of Yall need any? |
#2
Posted to rec.audio.tubes
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What is a 4X250F?
In article .com,
diecasthoop wrote: I have a few of these I got in a box of tubes. What are they used for? They are strange looking guys. Any of Yall need any? One use of these tubes was in the cutting amplifiers used to cut the old vinyl records, where a pair could provide 500 Watts or so of drive to the cutter head. If you have 4 of them they could be used to build a nice high power stereo amplifier. Regards, John Byrns -- Surf my web pages at, http://fmamradios.com/ |
#3
Posted to rec.audio.tubes
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What is a 4X250F?
In article .com,
Bret Ludwig wrote: On Jul 31, 4:28 pm, John Byrns wrote: In article .com, diecasthoop wrote: I have a few of these I got in a box of tubes. What are they used for? They are strange looking guys. Any of Yall need any? One use of these tubes was in the cutting amplifiers used to cut the old vinyl records, where a pair could provide 500 Watts or so of drive to the cutter head. If you have 4 of them they could be used to build a nice high power stereo amplifier. If one were wanting to use such a type in audio one would use the 4CS250, a conduction cooled variant, and heat sink it to a VERY large aluminum plate via a beryllium oxide link. On the contrary, the Fairchild stereo cutting system used 4 of the forced air cooled version of this tube in the stereo power amplifier that drove the cutting head. In other words, only a ****head would persist very far with building an audio amp around them. It would be like putting a Jaguar six cylinder engine in an airplane. How so, are you calling Fairchild a "****head"? You were just praising Fairchild in a parallel thread. On second thought you may be partially correct, now that I think about it, it was probably the 4CX150 that fairchild used, I will have to look it up. Regards, John Byrns -- Surf my web pages at, http://fmamradios.com/ |
#4
Posted to rec.audio.tubes
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What is a 4X250F?
OK, in the trash they go. Wife is bitching all the time about junk
gathering dust I will never use. |
#5
Posted to rec.audio.tubes
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What is a 4X250F?
On Tue, 31 Jul 2007 12:54:52 -0700, diecasthoop
wrote: I have a few of these I got in a box of tubes. What are they used for? They are strange looking guys. Any of Yall need any? This family was very common for VHF transmitter finals in point-to-point service when I was in the Army. Track24 era, anyone? PCM was just coming into use; digital audio was considered so secure that it didn't need to be manipulated at all; raw transmissions were considered secure. And even in that era, only a captured American receiver could have made any sense of even frequency-division-multiplexed telephone signals. You're making me feel old. OTOH, what doesn't? Some VHF ham guy will likely want your box of tubes. Put 'em in a visible spot, and expect your reward in Heaven. All good fortune, Chris Hornbeck "I would much rather be able to say it sounds like such and such, but when it's not obvious distortion and/or noise, when the specs are really good for those factors and IM and slew rate and a host of other stuff I probably can't bring to consciousness right now, yet one preamp lets me hear as if the source is alive and right there, and the next one makes me feel as if I'm listening to the equivalent of a very detailed cardboard Elvis, I don't know what words to offer that might help. But hell, I'm willing to try. Everything we might like to know isn't known yet, and through history people have come up with ways to measure stuff that previously went unmeasured." - Hank Alrich 07 May 2005 |
#6
Posted to rec.audio.tubes
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What is a 4X250F?
In article ,
Chris Hornbeck wrote: On Tue, 31 Jul 2007 12:54:52 -0700, diecasthoop wrote: I have a few of these I got in a box of tubes. What are they used for? They are strange looking guys. Any of Yall need any? This family was very common for VHF transmitter finals in point-to-point service when I was in the Army. Track24 era, anyone? PCM was just coming into use; digital audio was considered so secure that it didn't need to be manipulated at all; raw transmissions were considered secure. When was that, I didn't know that there was ever a time that raw PCM was considered secure? And even in that era, only a captured American receiver could have made any sense of even frequency-division-multiplexed telephone signals. I would think it would be child's play to make sense of FDM telephone signals, why would a captured American receiver be needed? Regards, John Byrns -- Surf my web pages at, http://fmamradios.com/ |
#7
Posted to rec.audio.tubes
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What is a 4X250F?
On Wed, 01 Aug 2007 03:51:18 GMT, John Byrns
wrote: PCM was just coming into use; digital audio was considered so secure that it didn't need to be manipulated at all; raw transmissions were considered secure. When was that, I didn't know that there was ever a time that raw PCM was considered secure? 1970. It was a simpler, but no less mean, time. Sadly. I would think it would be child's play to make sense of FDM telephone signals, why would a captured American receiver be needed? 1970. We were fighting starving peasants, which helped. Thanks, as always, Chris Hornbeck "I would much rather be able to say it sounds like such and such, but when it's not obvious distortion and/or noise, when the specs are really good for those factors and IM and slew rate and a host of other stuff I probably can't bring to consciousness right now, yet one preamp lets me hear as if the source is alive and right there, and the next one makes me feel as if I'm listening to the equivalent of a very detailed cardboard Elvis, I don't know what words to offer that might help. But hell, I'm willing to try. Everything we might like to know isn't known yet, and through history people have come up with ways to measure stuff that previously went unmeasured." - Hank Alrich 07 May 2005 |
#8
Posted to rec.audio.tubes
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What is a 4X250F?
There are many different versions of the 4x250 family. You will find
similar tubes as the 4cx250 and 4x150/4cx150 (little brother) around. The 4x means glass body sealed tetrode with 250 watts plate diss when you properly cool it with an adequate size blower. A ceramic type body seal "upgrade" makes the current tube a 4CX250. The various trailing letters often indicate the tube version, heater voltage and socket type. So your tube is a 26.5 volt (ac or dc) Beam Power tube. The higher heater voltage means your tube were not as popular in the consumer market or with amateurs so they are often found much cheaper on the surplus market. You can also see they have special socket and chimney requirements and often operate around +2,000 volts for typical operation. And once again forced air is required. The tubes are not extra linear in AB2 grounded grid operation so you must consider how to properly use/operate them. Since they are industry work-horse power tubes you can/will find them rf amplifiers, plasma cutter/generator circuits and similar circuits. They have been used in some audio amplifier circuits but the higher anode potentials and operational requirements make the more than unwieldy to use in most audio locations. There is a Yahoo group related to rfamplifiers, which is free to join. Please drop in if you're interested in these sort of amplifier topics (not limited to rf). http://groups.yahoo.com/group/rfamplifiers/ Great tubes for an amplifier project... don't throw them away. cheers, skipp : diecasthoop wrote: : I have a few of these I got in a box of tubes. What are they used for? : They are strange looking guys. Any of Yall need any? |
#9
Posted to rec.audio.tubes
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What is a 4X250F?
In article ,
Chris Hornbeck wrote: On Wed, 01 Aug 2007 03:51:18 GMT, John Byrns wrote: PCM was just coming into use; digital audio was considered so secure that it didn't need to be manipulated at all; raw transmissions were considered secure. When was that, I didn't know that there was ever a time that raw PCM was considered secure? 1970. It was a simpler, but no less mean, time. Sadly. It may have been a simpler time, but I can assure you from personal experience that "raw PCM" was not considered secure in 1970. That is not to say that there may not have been some people using "raw PCM" when it should have been encrypted. Regards, John Byrns -- Surf my web pages at, http://fmamradios.com/ |
#10
Posted to rec.audio.tubes
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What is a 4X250F?
"John Byrns" wrote in message
In article , Chris Hornbeck wrote: On Wed, 01 Aug 2007 03:51:18 GMT, John Byrns wrote: PCM was just coming into use; digital audio was considered so secure that it didn't need to be manipulated at all; raw transmissions were considered secure. When was that, I didn't know that there was ever a time that raw PCM was considered secure? 1970. It was a simpler, but no less mean, time. Sadly. It may have been a simpler time, but I can assure you from personal experience that "raw PCM" was not considered secure in 1970. That is not to say that there may not have been some people using "raw PCM" when it should have been encrypted. In the late 1960s I served at a Hawk site south of Miami that used a digital RF link to receive and share real time command and control information. My recollection is that the link was enciphered. The enciphering box had the only DIP TTL chips in the whole battery - the rest was tubes and discrete semiconductors. |
#11
Posted to rec.audio.tubes
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What is a 4X250F?
On Wed, 01 Aug 2007 18:57:46 GMT, John Byrns
wrote: It may have been a simpler time, but I can assure you from personal experience that "raw PCM" was not considered secure in 1970. That is not to say that there may not have been some people using "raw PCM" when it should have been encrypted. Maybe so, but you'll have to take it up with the US Army. Wasn't my call. Thanks, as always, Chris Hornbeck "I would much rather be able to say it sounds like such and such, but when it's not obvious distortion and/or noise, when the specs are really good for those factors and IM and slew rate and a host of other stuff I probably can't bring to consciousness right now, yet one preamp lets me hear as if the source is alive and right there, and the next one makes me feel as if I'm listening to the equivalent of a very detailed cardboard Elvis, I don't know what words to offer that might help. But hell, I'm willing to try. Everything we might like to know isn't known yet, and through history people have come up with ways to measure stuff that previously went unmeasured." - Hank Alrich 07 May 2005 |
#12
Posted to rec.audio.tubes
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What is a 4X250F?
Bret Ludwig wrote:
The 4X250 is a 4CX250 derivative. It probably has a glass underseal instead of the ceramic of the 4CX. I'm guessing C is for ceramic since transmitting types of this family that do not have the C usually have a glass section through which the bright filament-operating at domestic lightbulb color temperature more or less-is visible. Neither the 4X150 or the 4CX250 types used a bright tungsten filament. Both use indirectly heated cathodes, operating at modest temperatures. Bob Weiss N2IXK |
#13
Posted to rec.audio.tubes
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What is a 4X250F?
: Bret Ludwig wrote:
: Great tubes for an amplifier project... don't throw them away. : An RF amplifier in a repeater or radio room rack, sure. It's not a big deal to build a desktop 4cx250 amplifier. Many have been made and even some commercial units. But the 4cx tube family is not the most practical consumer audio tube. : The ARRL handbooks still show tube linears so people are still : building them to some extent. They can be a great dollar per watt value and fun to build if like any electronics project... you're willing to do the work. : The needed blower is a Dayton centrifugal one but some people use : converted vacuum cleaner motors. Keyword is blower... a fan just doesn't move enough air with the right amount of pressure to cool the tube(s). Doesn't have to be a Dayton brand blower. I don't know if a vacuum cleaner blower would be practical to adapt and you'd always want to check it for enough air. : If you like to listen to the stereo with the vacuum running then.... Anyone with experience knows you can find low noise blowers and learn how they are mounted to minimize heat. Don't be silly now... a casual stereo music listener is probably not going to use these type of tubes. : you still need a 10-20K:4/8/16 output transformer that is rated for : 4 kV working on the primary for, oh, 300 watts. The transformer is not going to be some off the shelf item you can find without doing a lot of homework... but they are around and can be spec'd for a project. Regardless it would be large in size and quite costly. Surplus audio transformers of the 4x/4cx tube family parameters are not easily found anymore. : This is the reason why power tubes bigger than 811s or 211s find : little commercial audio application. Sure you can build a delightful : amp around a pair of 4-400s or 5-125s or any of ten other cool looking : Eimac or WE/Machlett types...but the transformer is infeasible. Varian : EIMAC absolutely hated audio for whatever reason and refused to : consider making the low mu triodes audio people wanted. One person from early tube amplifier history once told me the tube selection process for amplifiers his company produced were based on size and anode voltage first. They did not want to deal with 2kv plate potentials in a consumer device. Consumer Audio was not the market Eimac was selling to... Most people often listen to less than 10 watts of real audio better than probably 80% of the time. : Al Bereskin built a twin 4-1000A power amp which is described in the : Journal of the IRE somewhere. The opt is a monster-but it's a voice : band only affair at that. And a bit of work to make a voice band only unit. If he built the amplifier in an AB1 layout he would have had to worry about parasitic oscillations and design the audio amplifier not to be an oscillator. Not an easy task for the amateur or first time builder(s). : A considerable body of knowledge exists on : the building of LF wideband magnetics in the 1-10 kW range, because : they were used in submarine and surface ship sonar applications. Much : of it, fifty years on even, is classified today but a good search of : library resources will reveal a few unclassified publications that are : quite explicit. Generally transformers in these voltage classes are : oil filled. A modern day toroid transformer would work just fine with many less demons. But you end up with an amplifier that costs 30dB more than you had hoped. cheers, s. |
#14
Posted to rec.audio.tubes
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What is a 4X250F?
: The needed blower is a Dayton centrifugal one but some people use : converted vacuum cleaner motors. Keyword is blower... a fan just doesn't move enough air with the right amount of pressure to cool the tube(s). Doesn't have to be a Dayton brand blower. I don't know if a vacuum cleaner blower would be practical to adapt and you'd always want to check it for enough air. Most of them were Daytons. Not all. Royal the vacuum company supplied a few. AiResearch which became Garrett did a few too. : If you like to listen to the stereo with the vacuum running then.... Anyone with experience knows you can find low noise blowers and learn how they are mounted to minimize heat. Don't be silly now... a casual stereo music listener is probably not going to use these type of tubes. : you still need a 10-20K:4/8/16 output transformer that is rated for : 4 kV working on the primary for, oh, 300 watts. The transformer is not going to be some off the shelf item you can find without doing a lot of homework... but they are around and can be spec'd for a project. Regardless it would be large in size and quite costly. Surplus audio transformers of the 4x/4cx tube family parameters are not easily found anymore. They were never ever surplus. None had low impedance voice coil windings AFAIK. : This is the reason why power tubes bigger than 811s or 211s find : little commercial audio application. Sure you can build a delightful : amp around a pair of 4-400s or 5-125s or any of ten other cool looking : Eimac or WE/Machlett types...but the transformer is infeasible. Varian : EIMAC absolutely hated audio for whatever reason and refused to : consider making the low mu triodes audio people wanted. One person from early tube amplifier history once told me the tube selection process for amplifiers his company produced were based on size and anode voltage first. They did not want to deal with 2kv plate potentials in a consumer device. Consumer Audio was not the market Eimac was selling to... Most people often listen to less than 10 watts of real audio better than probably 80% of the time. Many people contacted Eimac about getting a purpose built audio triode over the years. Including myself. They avoided that like the plague. The bottom line was if there wasn't a government tit somewhere they were not interested. The 3-500Z they made for years strictly for hams but the rest of their tubes had government customers. They even made a special small signal diode that went into HP VTVM probes. |