|
30L6GT equivalent to 50L6GT
Just changed some tubes in my S-38 and the original 50L6GT was changed
to 30L6GT by my tube supplier. I know that it is the audio output tube, but listening to it does not seem to make any difference. Is there a difference? Should I pull the tube and use the 50? Thanks -- |
30L6GT equivalent to 50L6GT
On Sun, 4 Jan 2009, Count Floyd wrote:
Just changed some tubes in my S-38 and the original 50L6GT was changed to 30L6GT by my tube supplier. I know that it is the audio output tube, but listening to it does not seem to make any difference. Is there a difference? Should I pull the tube and use the 50? Thanks Yes. The first number is the voltage of the filament. Most equipment would have tubes starting in 6 or 12, indicating 6 and 12 volts, but in some equipment they had no transformer to drop the voltage down to filament voltage level, so they put the filaments in series. Since there were only a handful of tubes in the unit, they used tubes created for the purpose, which had higher filament voltages. The 50L6GT requires a 50volt filament, and thus uses up just under half the AC line, making it easier to drop the rest of the voltage. It was common to have rectifier that used 35v on the filament, which then totals 85 and only about 30 volts more were needed. That can be made up of 12 and 6 volt filament tubes. By using a 30L6GT in the radio, you've caused all the other tubes to see a higher filament voltage. At the very least, that will cause a shortened life for the tubes. Michael VE2BVW |
30L6GT equivalent to 50L6GT
"Count Floyd" wrote in message news:BJ4mQCBKg9HM-pn2-3dWudjBJPujT@localhost... Just changed some tubes in my S-38 and the original 50L6GT was changed to 30L6GT by my tube supplier. I know that it is the audio output tube, but listening to it does not seem to make any difference. Is there a difference? Should I pull the tube and use the 50? Thanks -- Add up the tube filament voltages and see which tube is closest to what your line voltage. I'd think that the 50L6 would be preferable. |
30L6GT equivalent to 50L6GT
"Count Floyd" ha scritto nel
messaggio news:BJ4mQCBKg9HM-pn2-3dWudjBJPujT@localhost... Just changed some tubes in my S-38 and the original 50L6GT was changed to 30L6GT by my tube supplier. I know that it is the audio output tube, but listening to it does not seem to make any difference. Is there a difference? Should I pull the tube and use the 50? Thanks -- Firstly the tube that was changed by your supplier should be a 35L6 not 30L6 (to my knowlegde the 30L6 does not exist). Secondly the 35L6 and the 50L6 are not exactly the same tube with a different filament voltage, As a matter of fact the 50L6 is a slightly more powerful tube, as witnessed by its somewhat higher power dissipation and by the fact that, despite the higher filament voltage, its filament current is the same as that of the 35L6 (that is 0.15A). This means that the 50L6 has more cathode emission. In any case, using a 35L6 instead of a 50L6 causes the filament voltage of all tubes in the series string to be too high by some 10%. If you have not used your radio with a 35L6 for a long time, I believe no damage has occurred, but it would anywy be wise to use the original 50L6. Regards. Tony I0JX |
30L6GT equivalent to 50L6GT
Count Floyd wrote:
Just changed some tubes in my S-38 and the original 50L6GT was changed to 30L6GT by my tube supplier. I know that it is the audio output tube, but listening to it does not seem to make any difference. Is there a difference? Should I pull the tube and use the 50? With American tubes, the numbers at the beginning are the filament voltage, the numbers at the end indicate the number of elements in the tube, and the letters in the middle are more or less random. The 50L6 and 30L6 tubes are variants of the classic 6L6, built with higher voltage filaments for series string radios. If you put a 30L6 in place of a 50L6, not only will it fail prematurely from the high filament voltage, but so will all the other tubes in the radio because they will also be seeing high filament voltages. You _can_ make it work by increasing the value of the series resistor on the filament string to make sure all the tubes are seeing the correct filament voltages. If you do this, write a note inside the case warning future users of the equipment about the modification. Why did you change the tubes in the first place? The old ones are probably all fine anyway. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
30L6GT equivalent to 50L6GT
On Sun, 4 Jan 2009 17:27:28 UTC, "Antonio Vernucci"
wrote: "Count Floyd" ha scritto nel messaggio news:BJ4mQCBKg9HM-pn2-3dWudjBJPujT@localhost... Just changed some tubes in my S-38 and the original 50L6GT was changed to 30L6GT by my tube supplier. I know that it is the audio output tube, but listening to it does not seem to make any difference. Is there a difference? Should I pull the tube and use the 50? Thanks -- Firstly the tube that was changed by your supplier should be a 35L6 not 30L6 (to my knowlegde the 30L6 does not exist). Tony, Thanks, it was a 35L6, a typo. Put the old 50L6 back in, it basically was just the rectifier tube that caused the problem, so I will not mess with what is working! Thanks Tony I0JX -- |
30L6GT equivalent to 50L6GT
On Sun, 4 Jan 2009 17:16:59 UTC, "Tio Pedro"
wrote: "Count Floyd" wrote in message news:BJ4mQCBKg9HM-pn2-3dWudjBJPujT@localhost... Just changed some tubes in my S-38 and the original 50L6GT was changed to 30L6GT by my tube supplier. I know that it is the audio output tube, but listening to it does not seem to make any difference. Is there a difference? Should I pull the tube and use the 50? Thanks -- Add up the tube filament voltages and see which tube is closest to what your line voltage. I'd think that the 50L6 would be preferable. Tio, Thanks for the advice. It was a 35L6, not a 30L6, but I put the 50L6 back in, it was not the problem, it was the rectifier tube, don't fix what works, right? Thanks |
30L6GT equivalent to 50L6GT
|
30L6GT equivalent to 50L6GT
|
30L6GT equivalent to 50L6GT
Richard Knoppow wrote:
The 50L6 is NOT a relative of the 6L6. It is a pentode power tube with 10 watts of plate dissipation compared to 19 watts for a 6L6. The 6L6 puts out about 2.5 times the power when operating as a single tube Class-1A aplifier. Other characteristics are also different. Yeesh! That is not good at all! That is a very misleading number in that case. What about the 25L6 then? I have pitched a lot of 25L6 tubes over the years because they showed low transconductance compared with a 6L6. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
30L6GT equivalent to 50L6GT
"Scott Dorsey" wrote in message ... Richard Knoppow wrote: The 50L6 is NOT a relative of the 6L6. It is a pentode power tube with 10 watts of plate dissipation compared to 19 watts for a 6L6. The 6L6 puts out about 2.5 times the power when operating as a single tube Class-1A aplifier. Other characteristics are also different. Yeesh! That is not good at all! That is a very misleading number in that case. What about the 25L6 then? I have pitched a lot of 25L6 tubes over the years because they showed low transconductance compared with a 6L6. --scott Its identical to the 50L6 except for the heater voltage and current. The numbering system for tubes was intended to be systematic but broke down pretty quickly because of the plethora of new tubes. The earliest system was chaotic with numbers but also prefix letters usually indicating the manufacturer. For instance, RCA prefixed its tubes with UX so a UX-210 is a 210 tube made by RCA but others also varied the numbers, I think DeForest used 5 in place of 2 so a Deforest 210 became a 510. The number-letter-number system began sometime around the early to mid 1930's. I used to know the exact date but its evaporated. Note that while the first number usually indicates the filament voltage that is not always true. For instance, Philco and others made "locktal" tubes, a variation of the octal type but with plain wire leads and a sort of locking base. These usually have a 7 as the prefix of the type number but mostly have 6.3V filaments. As usual in life chaos reigns supreme. -- -- Richard Knoppow Los Angeles WB6KBL |
30L6GT equivalent to 50L6GT
On Mon, 05 Jan 2009 09:54:36 -0500, Scott Dorsey wrote:
Richard Knoppow wrote: The 50L6 is NOT a relative of the 6L6. It is a pentode power tube with 10 watts of plate dissipation compared to 19 watts for a 6L6. The 6L6 puts out about 2.5 times the power when operating as a single tube Class-1A aplifier. Other characteristics are also different. Yeesh! That is not good at all! That is a very misleading number in that case. What about the 25L6 then? I have pitched a lot of 25L6 tubes over the years because they showed low transconductance compared with a 6L6. --scott AFAIK the numbering -- other than the filament voltage, and other than suffix letters -- is almost completely arbitrary; any similarities in functions between similarly numbered tubes in a marketing, rather than an engineering, decision. Even then, as Richard pointed out, the filament voltage sometimes isn't, and a 'G' variant of a metal tube often has different interelectrode capacitances than the parent tube or the 'GT' variant. -- Tim Wescott Control systems and communications consulting http://www.wescottdesign.com Need to learn how to apply control theory in your embedded system? "Applied Control Theory for Embedded Systems" by Tim Wescott Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html |
30L6GT equivalent to 50L6GT
Other two cases of inconsistency:
- the old 814 made by Taylor is a transmitting triode, whilst the 814 we all know is a power tetrode. - the 6BN8 is a noval twin diode - triode. But there also is an octal 6BN8 which is a twin-diode pentode. 73 Tony I0JX |
30L6GT equivalent to 50L6GT
Scott Dorsey wrote:
Richard Knoppow wrote: The 50L6 is NOT a relative of the 6L6. It is a pentode power tube with 10 watts of plate dissipation compared to 19 watts for a 6L6. The 6L6 puts out about 2.5 times the power when operating as a single tube Class-1A aplifier. Other characteristics are also different. Yeesh! That is not good at all! That is a very misleading number in that case. What about the 25L6 then? I have pitched a lot of 25L6 tubes over the years because they showed low transconductance compared with a 6L6. --scott Personal opinion of mine...I think the * manufacturers* intended a 35/50L6 to be a DESIGN replacement for the old 6L6 as applied to AA5 50s-60s radios. Walks the same walk but its a 150 volt tube. No question about it....its not very closely related if you're looking from a conventional 6L6 perspective. 25L6 is sort of a different animal not related to either of the two. -ex |
30L6GT equivalent to 50L6GT
"Bill M" wrote in message ... Scott Dorsey wrote: Richard Knoppow wrote: The 50L6 is NOT a relative of the 6L6. It is a pentode power tube with 10 watts of plate dissipation compared to 19 watts for a 6L6. The 6L6 puts out about 2.5 times the power when operating as a single tube Class-1A aplifier. Other characteristics are also different. Yeesh! That is not good at all! That is a very misleading number in that case. What about the 25L6 then? I have pitched a lot of 25L6 tubes over the years because they showed low transconductance compared with a 6L6. --scott Personal opinion of mine...I think the * manufacturers* intended a 35/50L6 to be a DESIGN replacement for the old 6L6 as applied to AA5 50s-60s radios. Walks the same walk but its a 150 volt tube. No question about it....its not very closely related if you're looking from a conventional 6L6 perspective. 25L6 is sort of a different animal not related to either of the two. -ex The characteristics of the 50L6 are so completely different from a 6L6 that its obvious that it was a purpose-designed tube. About the only similarity is the use of beam-forming plates to get higher efficiency than is possible using a conventional pentode. This design originated about the mid 1930's. I am not sure which tube employed it first, perhaps the 807. In some ways the 6l6 can be viewed as a single-ended version of the 807 although there are some differences other than construction. Also, most of the early octal-based tubes were derived from previously available large pin base tubes. I am not sure about the 50L6 although there were high-voltage heater types available previous to the octal base intended for similar applications, i.e., AC/DC receivers. According to the _RCA Receiving Tube Manual_ edition RC-19, the 25L6 is identical to the 50L6 except for the heater rating. There were modified versions of the 6L6: the original was a metal-shell tube but was followed by the 6L6G which originaly had a large partly pear-shaped envelope, this was followed some years later by the GA, GB, and GC versions. The GA has a low-loss base but there are other changes in the latter versions, mainly increases in screen grid dissipation. The GC is essentially the same tube as the 5881. This tube was intended for service in circuits such as the "ultralinear" audio amplifier where the screens are operated at the same potential as the plates, a condition which will cause short life in a standard 6L6. The manufacture of tubes is fascinating and much more complex than appears on the surface requiring the services of many specialists such as metalurgists, glass specialists, etc. There are two internal RCA training manuals about tube design and manufacture on Pete Millett's web site at: http://www.pmillett.com/tecnical_books_online.htm Which also has a great deal of other stuff of interest to boatanchor types including the 4th edition of the _Radiotron Designer's Handbook_. -- -- Richard Knoppow Los Angeles WB6KBL |
30L6GT equivalent to 50L6GT
Richard Knoppow wrote:
The characteristics of the 50L6 are so completely different from a 6L6 Thank you. |
30L6GT equivalent to 50L6GT
"Bill M" wrote in message ... Richard Knoppow wrote: The characteristics of the 50L6 are so completely different from a 6L6 Thank you. You're welcome:-) FWIW, here are some common combinations of tubes used in 5-tube AC/DC sets. These were typical but its not an exaustive list, there were other tubes designed for series string operation directly from the power line. In England and in Germany other tube types were designed for the same purposebut operating from 230/250 volt mains. In fact the famous and rare original tube used in the famous Telefunken/Neumann U-47 was originally intended for such use. It was chosen because the filament could be run off the microphone bias voltage, an economy move since it elmininated the need for a separate DC filament supply: C.1934, from the RCA RC-12 tube handbook: 6A7 Converter 78 Remote cut-off IF amplifier 77 Combination dual diode and triode (detector, AVC, first audio) 43 Audio output 25Z5 Rectifier Plus 150 ohm, 10 watt filament dropping resistor From the RCA tube handbook RC-19 (1959) Miniature tube types 12BE6 Converter 12BA6 Remote cut-off IF amplifier 12AV6 Combination dual diode-triode (second detector-AVC-first audio) 50C5 Audio output 35W4 Rectifier Two other examples: Hallicrafters S-38B, a five tube set typical of many of the early 1950s. 12SA7 Converter 12SK7 Remote cut-off IF amplifier/BFO 12SQ7 Combination dual diode-triode (second detector, AVC, first audio) 50L6 Audio output 35Z5 Rectifier The original S-38 was a six tube set with an additional 12SQ7 tube as BFO and noise limiter. In the S-38B the BFO was obtained by allowing the IF stage to regenerate, a circuit patented by Hallicrafters and the ANL was eliminated. I am including the S-38 because it is an application of the 35L6. S-38 (c. 1949) 12SA7 Converter 12SK7 Remote cut-off IF amplifier 12SQ7, No.1 Combination dual diode-triode (second detector, AVC, first audio) 12SQ7, No.2, BFO and Automatic Noise Limiter 35L6 Audio output 35Z5 Rectifier Note that the filament drop here is 118V and in the five tube circuit its 121 volts, all close enough to the 110V to 120V range for AC current at the time these sets were in use. DC voltage was common in some cities, notably New York, I think at around 110 volts. DC was convenient for operating traction motors of the sort used in elevators so it was continued until a surprizingly late date. DC was also available in some other US cities but its beyond my recall which ones. 110 VDC was also common on shipboard. -- -- Richard Knoppow Los Angeles WB6KBL |
30L6GT equivalent to 50L6GT
.. DC voltage was common in some cities, notably New York,
I think at around 110 volts. DC was convenient for operating traction motors of the sort used in elevators so it was continued until a surprizingly late date. DC was also available in some other US cities but its beyond my recall which ones. 110 VDC was also common on shipboard. Richard Knoppow Los Angeles WB6KBL 110VDC on ships, Oh yes! Partner and I repairing radar on one such ship, bravely plugged in our trusty Weller soldering gun and pulled the trigger. Nothing for a few seconds, and then a little curl of smoke. When trigger was released, it hissed, breathing fire and sparks out of ALL the air cooling vent slots. Throwing it on the deck and stomping on it only aggravated the fireworks. Stone faced Skipper calmly pulled plug from wall, and I think he lost some admiration of our technical competence. Old Chief Lynn, W7LTQ |
30L6GT equivalent to 50L6GT
Lynn wrote:
. DC voltage was common in some cities, notably New York, I think at around 110 volts. DC was convenient for operating traction motors of the sort used in elevators so it was continued until a surprizingly late date. DC was also available in some other US cities but its beyond my recall which ones. 110 VDC was also common on shipboard. Richard Knoppow Los Angeles WB6KBL 110VDC on ships, Oh yes! Partner and I repairing radar Shame that replies sometimes take a few hours to saturate the planet via Usenet. The man's AA5 * could be saturated in flames* before he has a chance to read this thread. :) If its not too late, bub, just throw it out on deck and let the "skipper" aka "wife" unplug or stomp on it. We're not talking a Julien Creek mega model that can't be killed, are we? Jess like The Old Chief said. on one such ship, bravely (snipped) Old Chief Lynn, W7LTQ Oh whit, mind my manners. What was the question? -Bill |
30L6GT equivalent to 50L6GT
In article ,
Bill M wrote: Scott Dorsey wrote: Richard Knoppow wrote: The 50L6 is NOT a relative of the 6L6. It is a pentode power tube with 10 watts of plate dissipation compared to 19 watts for a 6L6. The 6L6 puts out about 2.5 times the power when operating as a single tube Class-1A aplifier. Other characteristics are also different. Yeesh! That is not good at all! That is a very misleading number in that case. What about the 25L6 then? I have pitched a lot of 25L6 tubes over the years because they showed low transconductance compared with a 6L6. Personal opinion of mine...I think the * manufacturers* intended a 35/50L6 to be a DESIGN replacement for the old 6L6 as applied to AA5 50s-60s radios. Walks the same walk but its a 150 volt tube. I pulled out the HB-3 for this and wow... it sure IS different. Only 8.5 watts dissipation, versus 14 for even the baby 6V6. No question about it....its not very closely related if you're looking from a conventional 6L6 perspective. 25L6 is sort of a different animal not related to either of the two. According to the HB-3, the 25L6 has ten watts which is a bit more than the 50L6. Mine does not have a page for the 35L6 but there is a note saying the 35B5 is an equivalent. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
30L6GT equivalent to 50L6GT
110VDC on ships, Oh yes! Partner and I repairing radar on one such ship, bravely plugged in our trusty Weller soldering gun and pulled the trigger. Nothing for a few seconds, and then a little curl of smoke. When trigger was released, it hissed, breathing fire and sparks out of ALL the air cooling vent slots. Throwing it on the deck and stomping on it only aggravated the fireworks. Stone faced Skipper calmly pulled plug from wall, and I think he lost some admiration of our technical competence. Old Chief Lynn, W7LTQ Heh heh! Been there and done that. As the civilian navigator on the USNS Keithly (a re-commissioned and converted Navy cargo ship)in the late 60's, we had a number of newly-graduated "scientists" on board. The scientific and comms spaces had been converted via MG's for 120/240VAC. The staterooms were still 110DC. I shared a room with one such newby and, seeing that my Norelco shaver worked just fine, he plugged in his early style portable record player/radio/amp. When turned on, the requisite curl of smoke and bad odor emanated, ending the machine's life, early. I probably would not have liked his music, anyway. The thing is, you really had to force the plug into those DC sockets. As I recall, they're not quite the same as standard two-blade ac plugs. de K3HVG -- Posted Via Newsfeeds.com Premium Usenet Newsgroup Service ---------------------------------------------------------- http://www.Newsfeeds.com |
30L6GT equivalent to 50L6GT
"K3HVG" wrote in message ... 110VDC on ships, Oh yes! Partner and I repairing radar on one such ship, bravely plugged in our trusty Weller soldering gun and pulled the trigger. Nothing for a few seconds, and then a little curl of smoke. When trigger was released, it hissed, breathing fire and sparks out of ALL the air cooling vent slots. Throwing it on the deck and stomping on it only aggravated the fireworks. Stone faced Skipper calmly pulled plug from wall, and I think he lost some admiration of our technical competence. Old Chief Lynn, W7LTQ Heh heh! Been there and done that. As the civilian navigator on the USNS Keithly (a re-commissioned and converted Navy cargo ship)in the late 60's, we had a number of newly-graduated "scientists" on board. The scientific and comms spaces had been converted via MG's for 120/240VAC. The staterooms were still 110DC. I shared a room with one such newby and, seeing that my Norelco shaver worked just fine, he plugged in his early style portable record player/radio/amp. When turned on, the requisite curl of smoke and bad odor emanated, ending the machine's life, early. I probably would not have liked his music, anyway. The thing is, you really had to force the plug into those DC sockets. As I recall, they're not quite the same as standard two-blade ac plugs. de K3HVG My now very distant memory is that DC outlets had either one prong perpendicular to the other or both "horrizontal" where standard sockets are parallel and "vertical". Occasionally, one sees sockets made to accomodate either type of plug. I think 220V sockets also had some variation of this pattern. Plugging 120V stuff into 220 will also get some interesting, although short lived, results. -- -- Richard Knoppow Los Angeles WB6KBL |
30L6GT equivalent to 50L6GT
My now very distant memory is that DC outlets had either one prong perpendicular to the other or both "horrizontal" where standard sockets are parallel and "vertical". Occasionally, one sees sockets made to accomodate either type of plug. I think 220V sockets also had some variation of this pattern. Plugging 120V stuff into 220 will also get some interesting, although short lived, results. I've certainly seen those plugs. The original 28v DC accessory outlets in our CAP-converted M-135 ambulance had the one plug rotated 90 deg from the other to prevent problems. The thing is, at least on that ship, I was able to get the shaver plug into the socket.. as was the other guy?? Maybe one blade was much wider? I simply can't remember... de K3HVG -- Posted Via Newsfeeds.com Premium Usenet Newsgroup Service ---------------------------------------------------------- http://www.Newsfeeds.com |
| All times are GMT +1. The time now is 06:31 PM. |
Powered by vBulletin® Copyright ©2000 - 2025, Jelsoft Enterprises Ltd.
RadioBanter.com