6L6 max cathode current?
Speaking of blowing up some 6L6'es...
I want to use a 6L6WXT+ as a series voltage regulator for a quick experiment. I know this probably isn't the intended use for that tube, but it's what I have in stock. I would prefer to stay within the safe and sane limits - or at least not damage the tube - as I plan to build an amplifier with it at some point. I figured I'd rig the tube as a source follower and just drive the grid with a lab power supply to get the voltage I need. Open loop, quick & dirty. Should be alright... I've searched high and low to find the maximum cathode current of a 6L6. None of the data sheets I've found even mention it(!). Does any of you know?
I'm looking to drop 400 V down to 300 V at 150-160 mA. So Pa = 16 W - very well within the limits. But I'm not sure the cathode will handle the current...
~Tom
Speaking of blowing up some 6L6'es...
I want to use a 6L6WXT+ as a series voltage regulator for a quick experiment. I know this probably isn't the intended use for that tube, but it's what I have in stock. I would prefer to stay within the safe and sane limits - or at least not damage the tube - as I plan to build an amplifier with it at some point. I figured I'd rig the tube as a source follower and just drive the grid with a lab power supply to get the voltage I need. Open loop, quick & dirty. Should be alright... I've searched high and low to find the maximum cathode current of a 6L6. None of the data sheets I've found even mention it(!). Does any of you know?
I'm looking to drop 400 V down to 300 V at 150-160 mA. So Pa = 16 W - very well within the limits. But I'm not sure the cathode will handle the current...
~Tom
If this is just a temporary voltage requirement for a bench experiment, and regulation is not necessary, why not just crank down your 400 volt power supply with a variac on the input mains?
I have seen over 250 mA go through my trusty well used Shuguangs on the peaks of the sine wave. The average current was in the 150 mA range, but this was for short periods of time. My guess is that 150 is on the edge for long term continuous DC use.
I would second that. If you dont want to deal with a plate cap get a 6AV5 for $4 which is rated for 110 mA in sweep use. 160 is probably safe. The cathode is twice the size of the 6L6 Sovtek. The cheap choice would be a 6DQ6 (175 mA). The optimum, 6DQ5 (315 mA) about $10, or the 6LW6 (400 mA) not so cheap.
Or yes, a big mosfet. I have recently discovered the Fuji (I thought they made cameras) mosfets that are on sale at Allied Electronics. The 2SK3522 handles 500 volts, 21 AMPS! and dissipates 220 watts! Oh, yeah it costs $2.33 too. I got a bunch and I have not been able to blow one up yet! Need more voltage? Try the 2SK3675. 900 volts, 7 amps, 195 watts, and about 8 pF reverse transfer capacitance. This one is for a monster mosfet follower or PowerDrive circuit. Real expensive at $1.40. Yes I got a few.
Hmmm... The idea of using a variac dawned on me, but I don't own one. Given that they're almost free ($70 shipped for a 500 VA one) from [THAT AUCTION SITE], maybe I should get off my balls and get one. I just generally prefer to make do with what I have.
I wouldn't mind building a small tube collection. But I think I'll wait for a HAM swap meet or something to come to town before going on a buying frenzy. Though, getting a handful of inexpensive tubes from one of the on-line places wouldn't be out of the question either. Thanks George for the tube suggestions.
~Tom
I wouldn't mind building a small tube collection. But I think I'll wait for a HAM swap meet or something to come to town before going on a buying frenzy. Though, getting a handful of inexpensive tubes from one of the on-line places wouldn't be out of the question either. Thanks George for the tube suggestions.
~Tom
i know that el34 is a pentode and not a beam-tetrode. the 6CA7 EH screen grids light up like a christmas tree due to misalignment at 425V. the excuse from new sensor was poor, and not plausible. a pentode has a better electron distribution for the G2 than a beam tetrode where the G2 is exposed to the concentrated stream of electrons in a smaller area, if not positioned correctly in the shadow of G1.
i am working with the blass babies more than 40 years, and if a G2 melts, the effect is rumbling, at least in UL mode.
i am working with the blass babies more than 40 years, and if a G2 melts, the effect is rumbling, at least in UL mode.
I have probably 100 or so exapmles of most of the 6L6 type variants. They are scattered in different boxes in 3 different locations. If there is any interest I can make an attempt to get a lot of them in one location for a group photograph. I do have many of the classic types but most are not NOS. And no, I won't attempt to find the glow point of my NOS RCA black plates or the Sylvania STR's.
As a prelude to posting some family pictures (6L6 family), I've been looking over my various stashes. The 6BG6/GA is supposed to be a plain-Jane type with ~20W plate capability, with the Sylvania Mil "super" 6BG6GAs being a notable exception. It seems that the GE 6BG6GA may also be worthy of note. Most of the ones I've encountered have big plates with large heat dissipating fins - maybe another "super" in the making. The plain Sylvanias (yellow box types) have the skinny 6L6GB-type plates, not at all like the "super" tubes. Needless to say, I bought a couple of GEs to augment the ones I already have, but not any Sylvanias.
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6L6 types
the plate size and structures not always tell you what the tube can do: the max. cathode current emitted seems for me more important. means, with the same cathode surface and a larger plate it is most likely, that the tube runs cooler, but must have not more power. most 6L6 types have a much smaller cathode emission surface than a 6CA6 or similar. for the 6L6, 5881 etc., the russians and the chinese are the masters of confusion.
the plate size and structures not always tell you what the tube can do: the max. cathode current emitted seems for me more important. means, with the same cathode surface and a larger plate it is most likely, that the tube runs cooler, but must have not more power. most 6L6 types have a much smaller cathode emission surface than a 6CA6 or similar. for the 6L6, 5881 etc., the russians and the chinese are the masters of confusion.
I was thinking more in terms of the plate having a structure that would tolerate higher dissipation than the usual 20W. This could come in useful when operating at a higher plate voltage and wanting to draw an idle current in excess of the 20W plate dissipation rating but still well within the emission capability of the cathode. Don't know about the screen voltage rating, though, and since there are no apertures in the GE plates it'll be hard to tell when the screens start to take off.
On another note, I have a pair of CBS/Hytron 6BG6GAs with huge radiators spot welded to the screen support, like elephant ears....
All of these will be in the menengerie photos when I get around to it.
On another note, I have a pair of CBS/Hytron 6BG6GAs with huge radiators spot welded to the screen support, like elephant ears....
All of these will be in the menengerie photos when I get around to it.
tubes
sorry, as a german engineer, i dont know about that 6BG6GA. probably we never had that type in europe from european manufacturing, likely philips and their companies. beam tetrodes have not been used so much in europe, besides later in TV sets for deflection, not so much in audio. anyway, the 6L6 types are nice. i also like them. their design target was to increase efficiency by reducing heater power (at least at the end) the beam can cause some plate hot heating, and this needs extra coolingg finns at the place where the electron beam hits the plate.
have luck!
sorry, as a german engineer, i dont know about that 6BG6GA. probably we never had that type in europe from european manufacturing, likely philips and their companies. beam tetrodes have not been used so much in europe, besides later in TV sets for deflection, not so much in audio. anyway, the 6L6 types are nice. i also like them. their design target was to increase efficiency by reducing heater power (at least at the end) the beam can cause some plate hot heating, and this needs extra coolingg finns at the place where the electron beam hits the plate.
have luck!
The original 6BG6GA is an 807 with an octal base. Most of the world has seen 807's, since millions were made. Both of these were repurposed 6L6GA's. As the vacuum tube production ramped down several manufacturers (Sylvania in particular) had contracts to fulfill. It became standard practice to stuff the glass with whatever guts that were available that worked in the contract owners particular design. We are dealing with the exact same thing now with legacy IC's as the older wafer fabs are being shut down.
There have been several examples of some creative glass stuffing that get discovered as the tubes (probably designed for military or government spare equipment) make their way to the surplus market. The most unusual example is some 6AV5GA beam tetrode indirectly heated TV sweep tubes packaged and sold as 6B4GA's (A DHT). I have seen Sylvania and Philips EGC branded tubes but both are of Sylvania manufacture.
The 6BG6G was a 6L6GA with a different pinout and a plate cap so that a much higher plate voltage could be used. It was intended for use as a sweep tube in TV sets, but found its way into voltage regulator and pulse circuits in military equipment. Spare tubes for this equipment were made long after the production of 6L6GA's ended. For this reason you will find some 6BG6GA's stuffed with other guts. Most of them contain some variation of the 6L6GB or 6L6GC. The "super 6BG6GA" sold by SND sales contains 7027A guts.
Can I think that is a Shuguang 6L6GCR?
4 of them did work for many year in a Mesa Fifty/Fifty stereo power amp at 460V of anode voltage. I don't know at which current but with -49V of grid voltage. Now it's time to change it but Mesa doesn't still sell it. If I buy a 6L6GCR I will have some problems?
4 of them did work for many year in a Mesa Fifty/Fifty stereo power amp at 460V of anode voltage. I don't know at which current but with -49V of grid voltage. Now it's time to change it but Mesa doesn't still sell it. If I buy a 6L6GCR I will have some problems?
With 460V and -49V, a 6L6GC should work fine.
You need to be able to measure the current, if you want a long lifetime with them - there is a big range of current possible, when you buy.
Surplus Russian 6П3С-Е also work really well, but again, you need to check for the current. Surplus tubes often have gas (= grid current, unstable anode current).
You need to be able to measure the current, if you want a long lifetime with them - there is a big range of current possible, when you buy.
Surplus Russian 6П3С-Е also work really well, but again, you need to check for the current. Surplus tubes often have gas (= grid current, unstable anode current).
The problem is that who ask me to change the tubes want that it sound like now. Or rather like when they was new. I think that a 6L6GCR sounds different from 6L6WXT+, for example. I have a used pair at home and I'll ask him to try it. Whit that pair of 6L6WXT+ che current is about 26mA. It is rather cold but the there isn't the possibility to adjust it and I don't know if I can modify it.
For now can some one confirm the the tubes in the picture are 6L6GCR?
Always and anyway I'm afraid for m bad english.
For now can some one confirm the the tubes in the picture are 6L6GCR?
Always and anyway I'm afraid for m bad english.
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