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#1
Posted to rec.audio.tubes
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High heater-cathode voltage
On Fri, 01 Jan 2010 21:36:09 -0800, Alex wrote:
snip To be on a safer side I would like to use a tube with 200...250V cathode-to-heater rating. So far I have found 6CG7, 6BQ7A, 6BC8 which have 200V rating. I hope many of you, tube gurus, can easily quote more suitable part numbers. Would it be possible to bias the heater winding to a higher voltage, say 90v? That might allow a far larger choice of bottles. -- Mick (Working in a M$-free zone!) Web: http://www.nascom.info Filtering everything posted from googlegroups to kill spam. |
#2
Posted to rec.audio.tubes
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High heater-cathode voltage
Alex wrote:
Hello, I would ask for an advice from the tube experts. I need a double triode or a triode-pentode with high cathode-to-heater voltage rating, 200...250V. Cathode current -- not less than 15mA. Transconductance -- as large as possible. Amplification mu -- as large as possible, but not to the detriment of the former criteria. Envelope -- miniature 9-pin. Heater -- 6.3V. One section of this tube is to be used as a cathode follower. Under steady state conditions cathode voltage is expected to be around 80...110V, but during warm-up, transients or pull-down load removal it might rise higher. To be on a safer side I would like to use a tube with 200...250V cathode-to-heater rating. So far I have found 6CG7, 6BQ7A, 6BC8 which have 200V rating. I hope many of you, tube gurus, can easily quote more suitable part numbers. Thanks in advance! Regards, Alex You might well find it hard to find many more B9A tubes with greater hk ratings although you might like to look at the 12BH7 but it mu is lower than that of a 6CG7. Be careful with these ratings because in many cases they are not dc only ratings but the sum of dc and peak signal values. The normal way to work a CF such are you are thinking of is the elevate the heater voltage to around 75V or so above ground. Cheers ian Cheers Ian |
#3
Posted to rec.audio.tubes
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High heater-cathode voltage
On Jan 2, 12:36*am, "Alex" wrote:
Hello, I would ask for an advice from the tube experts. I need a double triode or a triode-pentode with high cathode-to-heater voltage rating, 200...250V. Cathode current -- not less than 15mA. Transconductance -- as large as possible. Amplification mu -- as large as possible, but not to the detriment of the former criteria. Envelope -- miniature 9-pin. Heater -- 6.3V. One section of this tube is to be used as a cathode follower. Under steady state conditions cathode voltage is expected to be around 80...110V, but during warm-up, transients or pull-down load removal it might rise higher.. To be on a safer side I would like to use a tube with 200...250V cathode-to-heater rating. So far I have found 6CG7, 6BQ7A, 6BC8 which have 200V rating. I hope many of you, tube gurus, can easily quote more suitable part numbers. Thanks in advance! Regards, Alex Can you use a separate transformer for this heater? That would solve your heater-cathode voltage problems. |
#4
Posted to rec.audio.tubes
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High heater-cathode voltage
Hello,
I would ask for an advice from the tube experts. I need a double triode or a triode-pentode with high cathode-to-heater voltage rating, 200...250V. Cathode current -- not less than 15mA. Transconductance -- as large as possible. Amplification mu -- as large as possible, but not to the detriment of the former criteria. Envelope -- miniature 9-pin. Heater -- 6.3V. One section of this tube is to be used as a cathode follower. Under steady state conditions cathode voltage is expected to be around 80...110V, but during warm-up, transients or pull-down load removal it might rise higher. To be on a safer side I would like to use a tube with 200...250V cathode-to-heater rating. So far I have found 6CG7, 6BQ7A, 6BC8 which have 200V rating. I hope many of you, tube gurus, can easily quote more suitable part numbers. Thanks in advance! Regards, Alex |
#5
Posted to rec.audio.tubes
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High heater-cathode voltage
On Jan 2, 4:36*pm, "Alex" wrote:
Hello, I would ask for an advice from the tube experts. I need a double triode or a triode-pentode with high cathode-to-heater voltage rating, 200...250V. Cathode current -- not less than 15mA. Transconductance -- as large as possible. Amplification mu -- as large as possible, but not to the detriment of the former criteria. Envelope -- miniature 9-pin. Heater -- 6.3V. One section of this tube is to be used as a cathode follower. Under steady state conditions cathode voltage is expected to be around 80...110V, but during warm-up, transients or pull-down load removal it might rise higher.. To be on a safer side I would like to use a tube with 200...250V cathode-to-heater rating. So far I have found 6CG7, 6BQ7A, 6BC8 which have 200V rating. I hope many of you, tube gurus, can easily quote more suitable part numbers. Thanks in advance! Regards, Alex If you are worried about heater-cathode voltages causing arcs or leakage, then make a floating dc heater supply which has a 100k resistance from the cathode to the negative side of the heater supply. The 100k will keep the heater voltage close to the cathode Vdc and Vac. The only trouble is that if the heater supply transformer winding is close to a mains winding then you'll have maybe some mains hum noise transfered to the cathode via the small amount of capacitance between windings. So you may need to bypass the heater supply to 0V via maybe 2uF which will charge up quickly. But then you effectively have a 100k + 2uF from cathode to 0V which may upset the signal working. Another method is to have a 6.3Vac : 6.3Vac transformer from an existing heater supply and arrange the secondary to have an electrostatic screen. Stray C is reduced to less than 75pF. The winding can have a CT and this is then connected to the cathode via say 10k to bias the winding. I have never ever needed to do such tricky things in any amplifier and I've never seen it done in any of many amps or gear I have have serviced. If you need to use such techniques, you should have become aware of the extra country miles you gotta travel to make sure the gear remains smoke and noise free. 6U8A and many video triode pentodes used in TV applications will have high gm you say you want. I suggest you browse other listed tri-pents in the old tube manuals. I never trust the 200Vdc rating for heater cathode voltages and I would always want the Ek-h to be less than 75V. I've seen failures in amps where stupid designers have had over 200V on triodes rated for only 90V. Patrick Turner. |
#6
Posted to rec.audio.tubes
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High heater-cathode voltage
On Jan 3, 7:39*am, "Alex" wrote:
"flipper" wrote in message news On Fri, 1 Jan 2010 21:36:09 -0800, "Alex" wrote: Hello, I would ask for an advice from the tube experts. I need a double triode or a triode-pentode with high cathode-to-heater voltage rating, 200...250V. Cathode current -- not less than 15mA. Transconductance -- as large as possible. Amplification mu -- as large as possible, but not to the detriment of the former criteria. Envelope -- miniature 9-pin. Heater -- 6.3V. One section of this tube is to be used as a cathode follower. Under steady state conditions cathode voltage is expected to be around 80...110V, but during warm-up, transients or pull-down load removal it might rise higher. As others have mentioned the traditional method is to bias the heater voltage but, making a guess from your numbers, there are some circuit tricks you could maybe use. The first obvious one is to prevent load removal. I.E. a permanent load in parallel with the one that might be removed. Second, put a SS diode from grid (diode anode) to cathode (diode cathode). That will pull down the driver tube's load (since it will drive into the CF load) when the tubes are non conducting keeping grid and cathode V low until they both conduct, at which point the diode drops out and the circuit operates normally. Your concern there is the nominal operating voltage on the follower (when operating) if all other tubes are removed (I.E. maximum power supply float under minimum load) but with the numbers given I'm guessing that should not be a problem. Having said that, it's debatable whether 'start up' is as much of a problem as it might seem because, with no current flow, cathode is not 'high' despite high grid V but the diode makes the issue moot. To be on a safer side I would like to use a tube with 200...250V cathode-to-heater rating. So far I have found 6CG7, 6BQ7A, 6BC8 which have 200V rating. I hope many of you, tube gurus, can easily quote more suitable part numbers. 200V is the normal 'max' and the only thing I can recall higher was a power pentode. The more common case is lower, like with some intended for (U.S.) 'line power'. Note, that *is* total DC and signal peak, for heater negative (your case). With heater positive it's 100VDC, peaks to 200V. Thanks. Though the silicon diode will not help from the load disconnection, it might help reduce positive bias on a cold tube. Well, I ended up using a pentode section of 6BX8 in a triode connection. It has plenty of current, a decent transconductance for low output impedance.. Triode connection mu is not directly quoted in the datasheet, but from the other operation point numbers it must be somewhere around 40, which is good. In all respects it is better than 6CG7 triode. Some disadvantage -- this tube is rather hungry on the heater: 0.75A. Regards, Alex- Hide quoted text - - Show quoted text - I much like to use EL84 or EL86 as driver triodes for output tubes. An EL84 typical triode set up is Ea = 250V, Ia = 15mA, giving Ra = 2k2, µ = 17, so gm = 7.7mAV. This is about like using 5 half triode sections of a 6CG7 all in parallel. The EL86 has Ra = about 1k5 and µ = 10, so gain is less, but hey, Ra is *very* low. 6CL6 is another choice.... Linearity is at least as good as 6CG7. If you wish to use EL84 as a CF or have a pair in µ-follower, and you have one cathode at +250V, then follow what I said before in a post about dedicated heater windings. Or bias a common heater supply up to +125V, which means you'll have 125V Vh-k difference for the top and bottom triodes. Or if you have a CF after a typical common cathode gain tube, use a negative -250V supply for the cathode load of the CF and CR couple the gain tube anode to the CF grid which is biased at 0V. Patrick Turner. |
#7
Posted to rec.audio.tubes
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High heater-cathode voltage
"flipper" wrote in message news On Fri, 1 Jan 2010 21:36:09 -0800, "Alex" wrote: Hello, I would ask for an advice from the tube experts. I need a double triode or a triode-pentode with high cathode-to-heater voltage rating, 200...250V. Cathode current -- not less than 15mA. Transconductance -- as large as possible. Amplification mu -- as large as possible, but not to the detriment of the former criteria. Envelope -- miniature 9-pin. Heater -- 6.3V. One section of this tube is to be used as a cathode follower. Under steady state conditions cathode voltage is expected to be around 80...110V, but during warm-up, transients or pull-down load removal it might rise higher. As others have mentioned the traditional method is to bias the heater voltage but, making a guess from your numbers, there are some circuit tricks you could maybe use. The first obvious one is to prevent load removal. I.E. a permanent load in parallel with the one that might be removed. Second, put a SS diode from grid (diode anode) to cathode (diode cathode). That will pull down the driver tube's load (since it will drive into the CF load) when the tubes are non conducting keeping grid and cathode V low until they both conduct, at which point the diode drops out and the circuit operates normally. Your concern there is the nominal operating voltage on the follower (when operating) if all other tubes are removed (I.E. maximum power supply float under minimum load) but with the numbers given I'm guessing that should not be a problem. Having said that, it's debatable whether 'start up' is as much of a problem as it might seem because, with no current flow, cathode is not 'high' despite high grid V but the diode makes the issue moot. To be on a safer side I would like to use a tube with 200...250V cathode-to-heater rating. So far I have found 6CG7, 6BQ7A, 6BC8 which have 200V rating. I hope many of you, tube gurus, can easily quote more suitable part numbers. 200V is the normal 'max' and the only thing I can recall higher was a power pentode. The more common case is lower, like with some intended for (U.S.) 'line power'. Note, that *is* total DC and signal peak, for heater negative (your case). With heater positive it's 100VDC, peaks to 200V. Thanks. Though the silicon diode will not help from the load disconnection, it might help reduce positive bias on a cold tube. Well, I ended up using a pentode section of 6BX8 in a triode connection. It has plenty of current, a decent transconductance for low output impedance. Triode connection mu is not directly quoted in the datasheet, but from the other operation point numbers it must be somewhere around 40, which is good. In all respects it is better than 6CG7 triode. Some disadvantage -- this tube is rather hungry on the heater: 0.75A. Regards, Alex |
#8
Posted to rec.audio.tubes
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High heater-cathode voltage
On Jan 4, 6:55*am, "Alex" wrote:
"flipper" wrote in message ... On Sat, 2 Jan 2010 20:08:30 -0800, "Alex" wrote: "flipper" wrote in message Ya lost me. My datasheets say the 6BX8 is a twin triode, u 25, gm 6700, 400mA heater. Sorry. A typo. Meant 6DX8. Video pentode, connected as a triode, makes a cathode follower. Triode section, quite not useless, with mu=65, works in another stage.. I don't know how much 'power' you need out of it but you might want to look at the 6AW8 and 6JW8. Similar but with 600mA heaters. Then there's the 6KT8, also 600mA, but the triode is u 100 with a 2.5W Pentode. About 2.5W would be enough with some margin. Thanks for reminding of 6AW8. I do have 6AW8 in my collection. Looks similar to 6DX8 for both triode and pentode. What is frustrating -- pinout is TOTALLY different, and I have already wired for 6DX8, which does the job fine. (Sometimes I wonder why not make the tubes of similar application pin compatible, as most of double triodes?). This is a fair question. Why do many noval base tri-pents and many others all have different damn pinouts? Why is it that there are many different railway guages and screw threads in the world when it would obviously be much more convenient for everyone if standard rail gauge was 4ft 8.5inch world wide and if the only metal threads were Metric threads which IMHO are the best, ie, the pitch is neither too fine or two coarse regardless of the application? Well, deliberate non conformist pin-outs, rail gauges and threads were all chosen to make sure a given radio could only be fitted with certain tubes and no others, and that only certain railway rolling stock could be used and only threads chosen by a manufacturer could be used. Such hegemony upon homogenious sizes and pinouts mean that once someone buys an RCA radio or TV set, only RCA tubes can be fitted, and once someone signs up to having say the broad gauge used in the USA then that's where they must buy the trains from, and the service packages. Ditto with threads on screws. If a country buys a Boeing aeroplane, then they must consequently use Boeing spare nuts and bolts, even though other cheaper speare parts brands might be quite suitable. Of course despite the lack of engineering standardization found world wide it has not prevented many bogus makers of parts for all sorts of things like companies with names like Phake-Aero-Parts P/ L, and if you were to examine aeroplane servicing with a magnifying glass you'd find many planes are flying around with nuts and bolts which are half the strength they should be. Some planes have highlighted the problem after falling from the sky. But I digress. Sometimes there are good reasons why triode-pentodes, or frequency converter tubes such as 6BE6 or 6AN7 have pin-outs different to substitutes, and mainly because the subs are not quite the same, and not real subs unless the circuit has a few real changes made to coils or R&C values to make things work best over a certain RF range. There is now a vast number of solid state integrated chips with more than 8 pins. And a vast number of applications or functions for such chips so having similar pinouts becomes a meaningless advantage to anyone. So as complexity of devices went beyond the garden variety twin triode we just didn't really need pin out compatibility. And in any case, with tri-pents or twin triodes with equal gain sections **it is not hard to change the socket wiring** to suit a different tube if we wish to switch say from 6CG7 to 12AU7, etc. BTW, usually 6DJ8/6922 are compatible in circuits designed for 6CG7 with *one major exception*, ie, the Ea used for the tube. 6CG7 have almost identical electronic rating data to 6SN7 so the Ea max could be up to around 300V without dange of arc overs within the tube. But I'd always limit Ea in 6DJ8 to 150V. In fact, I'd only want to use 6DJ8 in a power amp as an input triode in SE mode or as an input LTP balanced pair where the Ea is fine at 100V, and Ia can then be a healthy and safe 6mA so that you get a nice 5Vrms output from a low Ra device to drive a driver stage using something such as 6CG7, 12BH7, 12AU7, 6SN7, EL84, EL34 etc, but which are better suited to producing up to 100Vrms output with Ea a typical +250V. Patrick Turner. So far the mains transformer is not overly hot and heater voltage (6.1Vac) is still reasonable. However the tranny is struggling a bit at warm-up. Pilot globe is noticeably dimmer on turn on. Well, better for the tubes -- less inrush current. If later I find I need to reduce power consumption, I will take the trouble to rewire. At 450mA heater power there's the 6JW8 with a triode at 70 but the pentode is only 1.2W. And the 6CM8 with a triode at 100 and a 2W pentode. But gm is lower for both compared to the others. If you're going to burn 750mA, though, why not the 6LY8? Triode is 100 and gm on the pentode is 20k. I almost used those in my 'PC Speaker' amp but it was too much power. 6LY8 sounds exotic. I do not have such a beast in my collection. Must be just pre-tube-extinction release. Regards, Alex- Hide quoted text - - Show quoted text - |
#9
Posted to rec.audio.tubes
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High heater-cathode voltage
"flipper" wrote in message Ya lost me. My datasheets say the 6BX8 is a twin triode, u 25, gm 6700, 400mA heater. Sorry. A typo. Meant 6DX8. Video pentode, connected as a triode, makes a cathode follower. Triode section, quite not useless, with mu=65, works in another stage. |
#10
Posted to rec.audio.tubes
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High heater-cathode voltage
"Patrick Turner" wrote in message ... If you are worried about heater-cathode voltages causing arcs or leakage, then make a floating dc heater supply which has a 100k resistance from the cathode to the negative side of the heater supply. The 100k will keep the heater voltage close to the cathode Vdc and Vac. The only trouble is that if the heater supply transformer winding is close to a mains winding then you'll have maybe some mains hum noise transfered to the cathode via the small amount of capacitance between windings. So you may need to bypass the heater supply to 0V via maybe 2uF which will charge up quickly. But then you effectively have a 100k + 2uF from cathode to 0V which may upset the signal working. Another method is to have a 6.3Vac : 6.3Vac transformer from an existing heater supply and arrange the secondary to have an electrostatic screen. Stray C is reduced to less than 75pF. The winding can have a CT and this is then connected to the cathode via say 10k to bias the winding. I have never ever needed to do such tricky things in any amplifier and I've never seen it done in any of many amps or gear I have have serviced. If you need to use such techniques, you should have become aware of the extra country miles you gotta travel to make sure the gear remains smoke and noise free. 6U8A and many video triode pentodes used in TV applications will have high gm you say you want. I suggest you browse other listed tri-pents in the old tube manuals. Yes, many oscillator-mixer tubes are suitable, 6AN8, 6AW8, 6EA8, 6JW8, but they are marginal in terms of power dissipation. The best from my junk box was 6DX8: video pentode (4W plate) + triode with mu=65. I never trust the 200Vdc rating for heater cathode voltages and I would always want the Ek-h to be less than 75V. I've seen failures in amps where stupid designers have had over 200V on triodes rated for only 90V. My greatest sin though is that this is not for an amplifier. I am rebuilding a vintage sweep-oscillator. It has magnetic frequency modulation -- RF coils are wound on ferrite rods between the poles of an electro-magnet with permanent nagnet bias. from the modern view point, the design is quite brainless -- frequency modulation (sweep) is sinusoidal, just by applying mains voltage to the electro-magnet coil. Instead of that I will make a saw-tooth modulation. like a vertical deflection TV circuit at a lower frequency, say 10Hz (10 sweeps per second). The cathode follower (CF) in question is for the RF oscillator amplitude stabilisation by way of anode modulation. CF load is virtually the whole RF oscillator circuit. Yes it is boot-strapped, so to get the highest gain I would like to have higher mu in the CF, as well as high transconductance. Perhaps I might the CF pentode as a pentode and boot-strap the whole screen grid of the CF, not only the load resistor of the previous stage (error amplifier). Probably this will give even higher gain. What do you think? Since number of the tube sockets is limited, I have to use combined tubes -- single EL84 per socket would be an unaffordable luxury. I need to squeeze a saw-tooth oscillator and the final "deflection" stage as well. Regards, Alex |
#11
Posted to rec.audio.tubes
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High heater-cathode voltage
flipper wrote:
On Sat, 2 Jan 2010 19:58:27 -0800 (PST), Patrick Turner wrote: On Jan 4, 6:55 am, "Alex" wrote: "flipper" wrote in message ... On Sat, 2 Jan 2010 20:08:30 -0800, "Alex" wrote: "flipper" wrote in message Ya lost me. My datasheets say the 6BX8 is a twin triode, u 25, gm 6700, 400mA heater. Sorry. A typo. Meant 6DX8. Video pentode, connected as a triode, makes a cathode follower. Triode section, quite not useless, with mu=65, works in another stage. I don't know how much 'power' you need out of it but you might want to look at the 6AW8 and 6JW8. Similar but with 600mA heaters. Then there's the 6KT8, also 600mA, but the triode is u 100 with a 2.5W Pentode. About 2.5W would be enough with some margin. Thanks for reminding of 6AW8. I do have 6AW8 in my collection. Looks similar to 6DX8 for both triode and pentode. What is frustrating -- pinout is TOTALLY different, and I have already wired for 6DX8, which does the job fine. (Sometimes I wonder why not make the tubes of similar application pin compatible, as most of double triodes?). This is a fair question. Why do many noval base tri-pents and many others all have different damn pinouts? Why is it that there are many different railway guages and screw threads in the world when it would obviously be much more convenient for everyone if standard rail gauge was 4ft 8.5inch world wide and if the only metal threads were Metric threads which IMHO are the best, ie, the pitch is neither too fine or two coarse regardless of the application? Well, deliberate non conformist pin-outs, rail gauges and threads were all chosen to make sure a given radio could only be fitted with certain tubes and no others, and that only certain railway rolling stock could be used and only threads chosen by a manufacturer could be used. Such hegemony upon homogenious sizes and pinouts mean that once someone buys an RCA radio or TV set, only RCA tubes can be fitted, and once someone signs up to having say the broad gauge used in the USA then that's where they must buy the trains from, and the service packages. Ditto with threads on screws. If a country buys a Boeing aeroplane, then they must consequently use Boeing spare nuts and bolts, even though other cheaper speare parts brands might be quite suitable. Of course despite the lack of engineering standardization found world wide it has not prevented many bogus makers of parts for all sorts of things like companies with names like Phake-Aero-Parts P/ L, and if you were to examine aeroplane servicing with a magnifying glass you'd find many planes are flying around with nuts and bolts which are half the strength they should be. Some planes have highlighted the problem after falling from the sky. But I digress. Pure crap. Boeing didn't 'invent' SAE threads nor, being a U.S. standard, are they the only ones that use them and while radio and TV set of the era often admonished to "use only insert brand tubes" virtually every tube type was made by everyone. As for rail gauge, every one of them was chosen for technical reasons that, at the time, seemed appropriate to the governing authorities and the U.S., as of 1863 (except the South), uses Standard/International gauge, not broad gauge. The South used broad gauge until 1886 when, in the stunning record time of 36 hours, the entire South was converted to Standard. Yes, but of course that is only in the USA which as we all know is only a very small part of the world and not the centre of the universe as some seem to think. Cheers Ian |
#12
Posted to rec.audio.tubes
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High heater-cathode voltage
On Sun, 03 Jan 2010 05:02:09 -0600, flipper wrote:
On Sun, 03 Jan 2010 10:20:50 +0000, Ian Bell wrote: flipper wrote: On Sat, 2 Jan 2010 19:58:27 -0800 (PST), Patrick Turner wrote: On Jan 4, 6:55 am, "Alex" wrote: "flipper" wrote in message ... On Sat, 2 Jan 2010 20:08:30 -0800, "Alex" wrote: "flipper" wrote in message Ya lost me. My datasheets say the 6BX8 is a twin triode, u 25, gm 6700, 400mA heater. Sorry. A typo. Meant 6DX8. Video pentode, connected as a triode, makes a cathode follower. Triode section, quite not useless, with mu=65, works in another stage. I don't know how much 'power' you need out of it but you might want to look at the 6AW8 and 6JW8. Similar but with 600mA heaters. Then there's the 6KT8, also 600mA, but the triode is u 100 with a 2.5W Pentode. About 2.5W would be enough with some margin. Thanks for reminding of 6AW8. I do have 6AW8 in my collection. Looks similar to 6DX8 for both triode and pentode. What is frustrating -- pinout is TOTALLY different, and I have already wired for 6DX8, which does the job fine. (Sometimes I wonder why not make the tubes of similar application pin compatible, as most of double triodes?). This is a fair question. Why do many noval base tri-pents and many others all have different damn pinouts? Why is it that there are many different railway guages and screw threads in the world when it would obviously be much more convenient for everyone if standard rail gauge was 4ft 8.5inch world wide and if the only metal threads were Metric threads which IMHO are the best, ie, the pitch is neither too fine or two coarse regardless of the application? Well, deliberate non conformist pin-outs, rail gauges and threads were all chosen to make sure a given radio could only be fitted with certain tubes and no others, and that only certain railway rolling stock could be used and only threads chosen by a manufacturer could be used. Such hegemony upon homogenious sizes and pinouts mean that once someone buys an RCA radio or TV set, only RCA tubes can be fitted, and once someone signs up to having say the broad gauge used in the USA then that's where they must buy the trains from, and the service packages. Ditto with threads on screws. If a country buys a Boeing aeroplane, then they must consequently use Boeing spare nuts and bolts, even though other cheaper speare parts brands might be quite suitable. Of course despite the lack of engineering standardization found world wide it has not prevented many bogus makers of parts for all sorts of things like companies with names like Phake-Aero-Parts P/ L, and if you were to examine aeroplane servicing with a magnifying glass you'd find many planes are flying around with nuts and bolts which are half the strength they should be. Some planes have highlighted the problem after falling from the sky. But I digress. Pure crap. Boeing didn't 'invent' SAE threads nor, being a U.S. standard, are they the only ones that use them and while radio and TV set of the era often admonished to "use only insert brand tubes" virtually every tube type was made by everyone. As for rail gauge, every one of them was chosen for technical reasons that, at the time, seemed appropriate to the governing authorities and the U.S., as of 1863 (except the South), uses Standard/International gauge, not broad gauge. The South used broad gauge until 1886 when, in the stunning record time of 36 hours, the entire South was converted to Standard. Yes, but of course that is only in the USA which as we all know is only a very small part of the world and not the centre of the universe as some seem to think. The "broad gauge used in the USA" is what he referenced so that's what I spoke directly to. When Stevenson invented his broad gauge here in the UK, he did a safety test that involved a complete train with steam loco and a broken rail on a high embankment. The train derailed (obviously) and ran down the embankment. The whole train remained upright during the test, and he was very upset when he was forced to conform to standard gauge for his railways. The bean counters had won again. d |
#13
Posted to rec.audio.tubes
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High heater-cathode voltage
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#14
Posted to rec.audio.tubes
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High heater-cathode voltage
"flipper" wrote in message ... On Sat, 2 Jan 2010 20:08:30 -0800, "Alex" wrote: "flipper" wrote in message Ya lost me. My datasheets say the 6BX8 is a twin triode, u 25, gm 6700, 400mA heater. Sorry. A typo. Meant 6DX8. Video pentode, connected as a triode, makes a cathode follower. Triode section, quite not useless, with mu=65, works in another stage. I don't know how much 'power' you need out of it but you might want to look at the 6AW8 and 6JW8. Similar but with 600mA heaters. Then there's the 6KT8, also 600mA, but the triode is u 100 with a 2.5W Pentode. About 2.5W would be enough with some margin. Thanks for reminding of 6AW8. I do have 6AW8 in my collection. Looks similar to 6DX8 for both triode and pentode. What is frustrating -- pinout is TOTALLY different, and I have already wired for 6DX8, which does the job fine. (Sometimes I wonder why not make the tubes of similar application pin compatible, as most of double triodes?). So far the mains transformer is not overly hot and heater voltage (6.1Vac) is still reasonable. However the tranny is struggling a bit at warm-up. Pilot globe is noticeably dimmer on turn on. Well, better for the tubes -- less inrush current. If later I find I need to reduce power consumption, I will take the trouble to rewire. At 450mA heater power there's the 6JW8 with a triode at 70 but the pentode is only 1.2W. And the 6CM8 with a triode at 100 and a 2W pentode. But gm is lower for both compared to the others. If you're going to burn 750mA, though, why not the 6LY8? Triode is 100 and gm on the pentode is 20k. I almost used those in my 'PC Speaker' amp but it was too much power. 6LY8 sounds exotic. I do not have such a beast in my collection. Must be just pre-tube-extinction release. Regards, Alex |
#15
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High heater-cathode voltage
"Patrick Turner" wrote in message ... Patrick: There is now a vast number of solid state integrated chips with more than 8 pins. And a vast number of applications or functions for such chips so having similar pinouts becomes a meaningless advantage to anyone. So as complexity of devices went beyond the garden variety twin triode we just didn't really need pin out compatibility. Alex: Thanks goodness (or whatever it is) that pinouts of the operational amplifiers in SO-8 and SO-14 and smaller packages are standardised, also transistors and MOSFETs in TO-126, TO-251, TO-252, TO-220, TO-263, SOT-23, SOT-223, etc. |
#16
Posted to rec.audio.tubes
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High heater-cathode voltage
"flipper" wrote in message The 6DX8's 9HX basing seems to be the 'oddball' as there's a whole slew of triode pentode pairs with 9DX basing. Could you please explain what "9HX basing" and "9DX basing" means? |
#17
Posted to rec.audio.tubes
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High heater-cathode voltage
"flipper" wrote in message ... On Sun, 3 Jan 2010 17:56:17 -0800, "Alex" wrote: "flipper" wrote in message The 6DX8's 9HX basing seems to be the 'oddball' as there's a whole slew of triode pentode pairs with 9DX basing. Could you please explain what "9HX basing" and "9DX basing" means? That's the EIA designation of the pinout 'standard'. For example, the 'same pin out' you mentioned for twin triodes is 9A (with 'half heater' pin 9), 9AJ (pin 9 is internal shield), and 9LP (no connection pin 9). They're not really identical but if you use pin 4-5 heater and NC on pin 9 they're 'compatible'. The 5670 twin triode is completely different, however, with 8CJ pinout and the 20EZ7 (20V heater 12AX7 for 'low cost stereos) is 9PG (possibly to move the heater pins for, hopefully, less hum susceptibility). I used the 20EZ7 in Tin Man. That number is usually located under/near the pin drawing on the tube datasheet. If you use Duncan's TDSL program you can search by pinout so, for example, you could locate all triode pentode pairs with 9DX. At least, all the ones his program knows about. That's what I did and observed few results for 9HX. I did that when I was contemplating the 'PC Speaker' amp because I considered making a PCB and having 'a lot of choices' seemed like it might be a good thing. That 6LY8 is also a 9DX, and the 6CX8, and the 6JE8, 6KR8, 6AU8, 6JV8 etc. Actually, the 6JV8 is almost identical to the 6AW8 and works as a direct sub in my 'PC Speaker' amp. The others would need component changes. Thanks, This is very useful. I installed that TDSL search program. |
#18
Posted to rec.audio.tubes
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High heater-cathode voltage
On Jan 3, 6:42*pm, flipper wrote:
On Sat, 2 Jan 2010 19:58:27 -0800 (PST), Patrick Turner wrote: On Jan 4, 6:55 am, "Alex" wrote: "flipper" wrote in message . .. On Sat, 2 Jan 2010 20:08:30 -0800, "Alex" wrote: "flipper" wrote in message Ya lost me. My datasheets say the 6BX8 is a twin triode, u 25, gm 6700, 400mA heater. Sorry. A typo. Meant 6DX8. Video pentode, connected as a triode, makes a cathode follower. Triode section, quite not useless, with mu=65, works in another stage. I don't know how much 'power' you need out of it but you might want to look at the 6AW8 and 6JW8. Similar but with 600mA heaters. Then there's the 6KT8, also 600mA, but the triode is u 100 with a 2.5W Pentode. About 2.5W would be enough with some margin. Thanks for reminding of 6AW8. I do have 6AW8 in my collection. Looks similar to 6DX8 for both triode and pentode. What is frustrating -- pinout is TOTALLY different, and I have already wired for 6DX8, which does the job fine. (Sometimes I wonder why not make the tubes of similar application pin compatible, as most of double triodes?). This is a fair question. Why do many noval base tri-pents and many others all have different damn pinouts? Why is it that there are many different railway guages and screw threads in the world when it would obviously be much more convenient for everyone if standard rail gauge was 4ft 8.5inch world wide and if the only metal threads were Metric threads which IMHO are the best, ie, the pitch is neither too fine or two coarse regardless of the application? Well, deliberate non conformist pin-outs, rail gauges and threads were all chosen to make sure a given radio could only be fitted with certain tubes and no others, and that only certain railway rolling stock could be used and only threads chosen by a manufacturer could be used. Such hegemony upon homogenious sizes and pinouts mean that once someone buys an RCA radio or TV set, only RCA tubes can be fitted, and once someone signs up to having say the broad gauge used in the USA then that's where they must buy the trains from, and the service packages. Ditto with threads on screws. If a country buys a Boeing aeroplane, then they must consequently use Boeing spare nuts and bolts, even though other cheaper speare parts brands might be quite suitable. Of course despite the lack of engineering standardization found world wide it has not prevented many bogus makers of parts for all sorts of things like companies with names like Phake-Aero-Parts P/ L, and if you were to examine aeroplane servicing with a magnifying glass you'd find many planes are flying around with nuts and bolts which are half the strength they should be. Some planes have highlighted the problem after falling from the sky. But I digress. Pure crap. Its not pure crap at all. I recently watched an accurate documentary where forensic crash experts determined that 3 of four bolts which held a tail rudder assembly onto a Norwegian plane were fake parts which broke due to being half the strength they should have been. The plane fell from the sky. Subsequent investigations in the US found fake parts had been installed on many planes including Air Force One, the US presidential plane. There are now firmer govt regulations in place concerning fake aircraft parts. Boeing didn't 'invent' SAE threads nor, being a U.S. standard, are they the only ones that use them and while radio and TV set of the era often admonished to "use only insert brand tubes" virtually every tube type was made by everyone. Yes sure, but there is much pin-out disparity between many triode- pentodes used in many TV sets so that substitution is impossible without rewiring the socket, let alone other circuit mods. It'd have been easier for all if all tri-pents always had the same pin outs for the same electrodes. As for rail gauge, every one of them was chosen for technical reasons that, at the time, seemed appropriate to the governing authorities and the U.S., as of 1863 (except the South), uses Standard/International gauge, not broad gauge. The South used broad gauge until 1886 when, in the stunning record time of 36 hours, the entire South was converted to Standard. Not so stunning really. The sleepers used for standard guage were shorter than for broad gauge, so they cost less. By 1886, there was no fear between north and south states of the USA that an invasion would happen. The nth and sth had finished fighting in 1865. Many of the nth and sth hate each other's guts to this day of course which shows there is not complete standardisation of emotional response between nth and sth. Meanwhile in Oz which has always had a tiny population but a land area nearly the size of Nth America. There were quite a number of different rail gauges for a long time before and after Oz had a Federal Govt in 1901. Before 1901, nobody could be sure there would not be a war between the States of Australia which were in effect like different countries under British umbrella rule. Ppl in Victoria didn't want trains full of tropps to be able to be shipped down from New South Wales. So the Victorians had broad guage, 5'3", NSW had standard, 4"8.5". Meanwhile in Queeensland the gauge was 3'6", and stopped invasion from NSW. Also Qld was a very large state, very low population and the cost of sleepers was a major concern and of course the sleepers were prone to termites, not to mention the whole rail system being sunject to regular flood damage. Victoria was the smallest sized state but had a vast abundance of eucalypt hardwoods which made ideal rail sleepers so the costs of them being longer didn't worry the Victorians. Melbourne was the effective capitol of Australia and the main economic centre before the states became officially united. Eventually after many years you could get a train trip from Sydney to Melbourne without the delays caused by changing bogies on carriages at the border crossings. Vic went to standard. It would be a dull world if everything was standardized. Some things, like women, could never be standardized. Patrick Turner. |
#19
Posted to rec.audio.tubes
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High heater-cathode voltage
On Jan 3, 10:15*pm, (Don Pearce) wrote:
On Sun, 03 Jan 2010 05:02:09 -0600, flipper wrote: On Sun, 03 Jan 2010 10:20:50 +0000, Ian Bell wrote: flipper wrote: On Sat, 2 Jan 2010 19:58:27 -0800 (PST), Patrick Turner wrote: On Jan 4, 6:55 am, "Alex" wrote: "flipper" wrote in message om... On Sat, 2 Jan 2010 20:08:30 -0800, "Alex" wrote: "flipper" wrote in message snip, The "broad gauge used in the USA" is what he referenced so that's what I spoke directly to. When Stevenson invented his broad gauge here in the UK, he did a safety test that involved a complete train with steam loco and a broken rail on a high embankment. The train derailed (obviously) and ran down the embankment. The whole train remained upright during the test, and he was very upset when he was forced to conform to standard gauge for his railways. The bean counters had won again. Yes, but testing trains and making conclusions about the guage and overturning moments during derailments was a very imprecise science indeed at the time of Stevenson. The bean counters soon realised that standard guage rolling stock construction costs could be reduced significanly with shorter axel length. So muct so that for a given British Pound, much more rolling stock could be made and the gains outweighed the advanatges of broad guage instability. Later during the peak of rail use in the 1950s where train speeds had increased to above 100MPH there was **** all safety advantage to be had by making rails wider apart, even though one could have had wider rolling stock with more floor area for more ppl or freight. The same sort of thinking applies to motor vehicles where the maximum width of a truck is about only 8 feet. We make our highways smooth and straight and the wheels can be close together. If you double the width of a train or truck, the costs of railways and roads soar way to high. If wider vehicles were allowed such as 15' wide Cadilacs with 12 seats, you'd still get ppl trying to drive one to work on road lanes 20' wide. Its been decided its more efficient to have lots of slim width vehicles following each other in series than half the number at double the width for the same road / track area. But on another planet Moduxium, in a distant galaxy they don't bother with wheels; they just have toobs where people stand for a few seconds before they are beamed up or down to the thousands of height levels of the population. Patrick Turner. |
#20
Posted to rec.audio.tubes
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High heater-cathode voltage
On Jan 4, 6:12*am, flipper wrote:
On Sun, 03 Jan 2010 11:15:02 GMT, (Don Pearce) wrote: On Sun, 03 Jan 2010 05:02:09 -0600, flipper wrote: On Sun, 03 Jan 2010 10:20:50 +0000, Ian Bell wrote: flipper wrote: On Sat, 2 Jan 2010 19:58:27 -0800 (PST), Patrick Turner wrote: On Jan 4, 6:55 am, "Alex" wrote: "flipper" wrote in message news:119uj59m68tjspq0erc8geu6ehi61n0gfe@4ax. com... On Sat, 2 Jan 2010 20:08:30 -0800, "Alex" wrote: "flipper" wrote in message Ya lost me. My datasheets say the 6BX8 is a twin triode, u 25, gm 6700, 400mA heater. Sorry. A typo. Meant 6DX8. Video pentode, connected as a triode, makes a cathode follower. Triode section, quite not useless, with mu=65, works in another stage. I don't know how much 'power' you need out of it but you might want to look at the 6AW8 and 6JW8. Similar but with 600mA heaters. Then there's the 6KT8, also 600mA, but the triode is u 100 with a 2.5W Pentode. About 2.5W would be enough with some margin. Thanks for reminding of 6AW8. I do have 6AW8 in my collection. Looks similar to 6DX8 for both triode and pentode. What is frustrating -- pinout is TOTALLY different, and I have already wired for 6DX8, which does the job fine. (Sometimes I wonder why not make the tubes of similar application pin compatible, as most of double triodes?). This is a fair question. Why do many noval base tri-pents and many others all have different damn pinouts? Why is it that there are many different railway guages and screw threads in the world when it would obviously be much more convenient for everyone if standard rail gauge was 4ft 8.5inch world wide and if the only metal threads were Metric threads which IMHO are the best, ie, the pitch is neither too fine or two coarse regardless of the application? Well, deliberate non conformist pin-outs, rail gauges and threads were all chosen to make sure a given radio could only be fitted with certain tubes and no others, and that only certain railway rolling stock could be used and only threads chosen by a manufacturer could be used. Such hegemony upon homogenious sizes and pinouts mean that once someone buys an RCA radio or TV set, only RCA tubes can be fitted, and once someone signs up to having say the broad gauge used in the USA then that's where they must buy the trains from, and the service packages. Ditto with threads on screws. If a country buys a Boeing aeroplane, then they must consequently use Boeing spare nuts and bolts, even though other cheaper speare parts brands might be quite suitable. Of course despite the lack of engineering standardization found world wide it has not prevented many bogus makers of parts for all sorts of things like companies with names like Phake-Aero-Parts P/ L, and if you were to examine aeroplane servicing with a magnifying glass you'd find many planes are flying around with nuts and bolts which are half the strength they should be. Some planes have highlighted the problem after falling from the sky. But I digress. Pure crap. Boeing didn't 'invent' SAE threads nor, being a U.S. standard, are they the only ones that use them and while radio and TV set of the era often admonished to "use only insert brand tubes" virtually every tube type was made by everyone. As for rail gauge, every one of them was chosen for technical reasons that, at the time, seemed appropriate to the governing authorities and the U.S., as of 1863 (except the South), uses Standard/International gauge, not broad gauge. The South used broad gauge until 1886 when, in the stunning record time of 36 hours, the entire South was converted to Standard. Yes, but of course that is only in the USA which as we all know is only a very small part of the world and not the centre of the universe as some seem to think. The "broad gauge used in the USA" is what he referenced so that's what I spoke directly to. When Stevenson invented his broad gauge here in the UK, he did a safety test that involved a complete train with steam loco and a broken rail on a high embankment. The train derailed (obviously) and ran down the embankment. The whole train remained upright during the test, and he was very upset when he was forced to conform to standard gauge for his railways. The bean counters had won again. You apparently have the same problem as Patrick in thinking cost is of no consequence but, besides that, there were other pros and cons in play. However, be that as it may be, what you or I think would have been the 'best railroad' isn't the issue. The issue was Patrick's absurdity that all these decisions were some sort of 'proprietary parts' conspiracy.- Hide quoted text - - Show quoted text - Well, another area where a lack of standardization occurs is with military gear and ammunition. You just don't want your enemy to steal your ammo and fire it all back at you through their guns. Patrick Turner. |
#21
Posted to rec.audio.tubes
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High heater-cathode voltage
"Patrick Turner" wrote in message
As for rail gauge, every one of them was chosen for technical reasons that, at the time, seemed appropriate to the governing authorities and the U.S., as of 1863 (except the South), uses Standard/International gauge, not broad gauge. The South used broad gauge until 1886 when, in the stunning record time of 36 hours, the entire South was converted to Standard. http://en.wikipedia.org/wiki/Broad_gauge " May 31, 1886. Over a period of 36 hours, tens of thousands of workers pulled the spikes from the west rail of all the broad gauge lines in the South, moved them 3 in (76 mm) east and spiked them back in place. The new gauge was close enough that standard gauge equipment could run on it without problem. By June 1886, all major railroads in North America were using approximately the same gauge. The final conversion to true standard gauge took place gradually as track was maintained." Not so stunning really. The sleepers used for standard guage were shorter than for broad gauge, so they cost less. By 1886, there was no fear between north and south states of the USA that an invasion would happen. The nth and sth had finished fighting in 1865. Many of the nth and sth hate each other's guts to this day of course which shows there is not complete standardisation of emotional response between nth and sth. Canny observation of life in the US. There has been a lot of cross-migration between the nth and the sth since the CW, which has tended to mitigate the hatred or at least break it up into smaller pockets. For example, if you go south in Florida, you go north culturally. Jacksonville, true to its name is part of the old South. By the time you get to Miami, it is almost like a little New YorK City with Cubans standing in for the Puerto Ricans. Go further south to Key West, and you're culturally in Maine. Meanwhile in Oz which has always had a tiny population but a land area nearly the size of Nth America. There were quite a number of different rail gauges for a long time before and after Oz had a Federal Govt in 1901. Before 1901, nobody could be sure there would not be a war between the States of Australia which were in effect like different countries under British umbrella rule. Ppl in Victoria didn't want trains full of tropps to be able to be shipped down from New South Wales. So the Victorians had broad guage, 5'3", NSW had standard, 4"8.5". Meanwhile in Queeensland the gauge was 3'6", and stopped invasion from NSW. Also Qld was a very large state, very low population and the cost of sleepers was a major concern and of course the sleepers were prone to termites, not to mention the whole rail system being sunject to regular flood damage. Victoria was the smallest sized state but had a vast abundance of eucalypt hardwoods which made ideal rail sleepers so the costs of them being longer didn't worry the Victorians. Melbourne was the effective capitol of Australia and the main economic centre before the states became officially united. Eventually after many years you could get a train trip from Sydney to Melbourne without the delays caused by changing bogies on carriages at the border crossings. Vic went to standard. Interesting. |
#22
Posted to rec.audio.tubes
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High heater-cathode voltage
On Jan 5, 11:06*pm, "Arny Krueger" wrote:
"Patrick Turner" wrote in message As for rail gauge, every one of them was chosen for technical reasons that, at the time, seemed appropriate to the governing authorities and the U.S., as of 1863 (except the South), uses Standard/International gauge, not broad gauge. The South used broad gauge until 1886 when, in the stunning record time of 36 hours, the entire South was converted to Standard. http://en.wikipedia.org/wiki/Broad_gauge " May 31, 1886. Over a period of 36 hours, tens of thousands of workers pulled the spikes from the west rail of all the broad gauge lines in the South, moved them 3 in (76 mm) east and spiked them back in place. The new gauge was close enough that standard gauge equipment could run on it without problem. By June 1886, all major railroads in North America were using approximately the same gauge. The final conversion to true standard gauge took place gradually as track was maintained." Not so stunning really. The sleepers used for standard guage were shorter than for broad gauge, so they cost less. By 1886, there was no fear between north and south states of the USA that an invasion would happen. The nth and sth had finished fighting in 1865. Many of the nth and sth hate each other's guts to this day of course which shows there is not complete standardisation of emotional response between nth and sth. Canny observation of life in the US. There has been a lot of cross-migration between the nth and the sth since the CW, which has tended to mitigate the hatred or at least break it up into smaller pockets. For example, if you go south in Florida, you go north culturally. Jacksonville, true to its name is part of the old South. By the time you get to Miami, it is almost like a little New YorK City with Cubans standing in for the Puerto Ricans. Go further south to Key West, and you're culturally in Maine. Meanwhile in Oz which has always had a tiny population but a land area nearly the size of Nth America. There were quite a number of different rail gauges for a long time before and after Oz had a Federal Govt in 1901. Before 1901, nobody could be sure there would not be a war between the States of Australia which were in effect like different countries under British umbrella rule. Ppl in Victoria didn't want trains full of tropps to be able to be shipped down from New South Wales. So the Victorians had broad guage, 5'3", NSW had standard, 4"8.5". Meanwhile in Queeensland the gauge was 3'6", and stopped invasion from NSW. Also Qld was a very large state, very low population and the cost of sleepers was a major concern and of course the sleepers were prone to termites, not to mention the whole rail system being sunject to regular flood damage. Victoria was the smallest sized state but had a vast abundance of eucalypt hardwoods which made ideal rail sleepers so the costs of them being longer didn't worry the Victorians. Melbourne was the effective capitol of Australia and the main economic centre before the states became officially united. Eventually after many years you could get a train trip from Sydney to Melbourne without the delays caused by changing bogies on carriages at the border crossings. Vic went to standard. Interesting.- Hide quoted text - - Show quoted text - I can never apply one perception of the people of the USA because it has a diverse range to consider. Some I like a lot, and others, well, I hope they improove. Australian people have also become multicultural and largely tolerant of others within itself. We could easily be an extra State of the Union, because we speak english and most of the US media and entertainment has brainwashed us ever since media and entertainment was invented. Its been a benign process, augmented by our clinging to Mother England for at least to about 1960. We'd like to become a Republic, and ditch the Queen of England as our figurehead monarch, but nobody here knows how to invite such a nice old lady to leave our Constitutuion. And we sure don't agree amoung ourselves about what we'd do about having a President; *whah*, that's way to difficult. Its a case of why change an antiquated system when it ain't broke, and its fairly harmless as it is. If we found we had some medling goon of a British royal as Head of State, then ppl here would push for the adoption of the next least worse system. One reason why we never quite ever wanted to fight a civil war over any damn thing was because by the time you travel to sort it out with the enemy, you've cooled down, especially considering there are so many pubs along the way, and its just so far to anywhere in Oz.... Patrick Turner. |
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Hello,
I've searched very much but maybe I'm not using good search terms, but I can't find a direct description of how to measure "heater cathode voltage". I mean, seemingly all tubes have a maximum "heater-cathode voltage" which may be X volts positive or negative. Everybody must already know how to measure this or else there would be some better references on the web. I however, do not. Would someone please point me to a reference of how to measure this parameter or provide their own description? |
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