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Anyone do Vacuum Tube design or similar still?

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Drac0nic

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Okay, this is probably somewhat of a long shot but I'm looking for the parent tube of the pentode in a 6LU8 or 6LR8 (identical except base/pinout) tubes or their 16/21V filament counterparts. I don't care if it's Compactron, Novar or just plain jane octal. Datasheet included for reference. The 6LU/LR have a triode, I don't care about that and may end up using a second one but I'd rather not have any extraneous sections I'm paying to heat. I am using this for a regulated power supply, so I don't think that it will make much difference if they're not 100% the same so log as I'm not pushing them to the absolute maximums.

https://frank.pocnet.net/sheets/107/6/6LU8.pdf
 

spec

Well-Known Member
Most Helpful Member
Okay, this is probably somewhat of a long shot but I'm looking for the parent tube of the pentode in a 6LU8 or 6LR8 (identical except base/pinout) tubes or their 16/21V filament counterparts. I don't care if it's Compactron, Novar or just plain jane octal. Datasheet included for reference. The 6LU/LR have a triode, I don't care about that and may end up using a second one but I'd rather not have any extraneous sections I'm paying to heat. I am using this for a regulated power supply, so I don't think that it will make much difference if they're not 100% the same so log as I'm not pushing them to the absolute maximums.

https://frank.pocnet.net/sheets/107/6/6LU8.pdf
Hi DO,

It would be a great help if you could post a schematic of your power supply.

But, off the top of my head, I would imagine these tubes would be worth looking at: EL84, EL34, 6V6GT. The latter is a beam tetrode if I remember correctly.

The pentode section that you show is for a TV line output, but do you need the high voltage required for a line output tube- I would think not unless you are making a very high voltage power supply.

You probably do not want to hear this, but you could make a much better power supply, even high voltage, with transistors.

spec
 

Drac0nic

New Member
Input V is about 340VDC currently. It's more of a prototype for something in the 650V range and maybe larger at a point(?) so I even if I ditch the hollow state later and go transistorized it shouldn't cost me much. Here is a schematic I based it on, it's from an HP-400 Oscilloscope. It's actually to mess around with other vacuum tube stuff.


I don't see transistorizing this being too difficult really, I'm likely going to get some 130V Zeners to ditch the 0D3 with as well. Overall the circuit seems to work well, I haven't load tested it yet but it certainly swings voltage about 80-90V with the stockish resistor combination. I'm hitting a hamfest this weekend so the oddball variants of these (21V Filament) may be on the list since they're only a few bucks each.
 

chemelec

Well-Known Member
I would probably use a zener regulated Mosfet circuit.
Shouldn't be too difficult and no filament transformer.
 

spec

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Input V is about 340VDC currently. It's more of a prototype for something in the 650V range and maybe larger at a point(?) so I even if I ditch the hollow state later and go transistorized it shouldn't cost me much. Here is a schematic I based it on, it's from an HP-400 Oscilloscope. It's actually to mess around with other vacuum tube stuff.


I don't see transistorizing this being too difficult really, I'm likely going to get some 130V Zeners to ditch the 0D3 with as well. Overall the circuit seems to work well, I haven't load tested it yet but it certainly swings voltage about 80-90V with the stockish resistor combination. I'm hitting a hamfest this weekend so the oddball variants of these (21V Filament) may be on the list since they're only a few bucks each.
Hi DO,

That is a standard rudimentary voltage regulator which will have a maximum output voltage dictated by the VAKmax of V7. The maximum output current will be dictated by IKmax of V6.

Good luck with the your project.

spec
 

Drac0nic

New Member
Quick update on this, I paired it with another compactron I had with the same pinout. I have about 80v swing and 60ma current capacity with any voltage in range.














I have tweaked it a bit, I may put in a smaller choke because I think the transformer is the limiting factor. I am getting about 40v drop at 60ma across it.

I have been attempting to build a solid state version and that certainly did not pass the smoke test! Schematic to come
 

crutschow

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The advantage of tubes is that they take much longer to smoke. :)
 

cowboybob

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Solid state is, optically, very, very boring... they add nothing to the ambience of a rig.

(For the purists out there, I am excluding any solid state device that emits photons - sure, they can get hot, but there is no "warmth".)
 

schmitt trigger

Well-Known Member
Draconic;
Power tubes would glow blue from stray electron emission, and were a joy to see that glow modulated with music.
But the glow appears on the glass' inner surface

The glow in regulator tubes is different......it is similar to neon tubes, in which all the gas inside would be glowing. A very soft, delicate glow.
 

Drac0nic

New Member
0D3 in the background. :) I should probably pick up some other voltages but may end up doing Zeners for the cost depending on the required voltages. No socket required which is a plus not to mention physical durability and space utilization. You certainly don't get the pretty glow however.

Then again there's also the 2SA15 which is its own oddball regulator.

http://www.radiomuseum.org/forum/2as15_how_it_works.html
 

audioguru

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Most Helpful Member
60 years ago my Heathkit amplifier output tubes glowed purple but the glow was not modulated by the signal.
Today you can by a solid state amplifier with tubes on top that glow but they are not part of the circuit. Then you can show your friends and let them hear your toobs amplifier.
 

Les Jones

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The last valves (Vacuum tubes.) that I use you could not see the blue glow or even the glow from the filiments as they were made of ceramic. They were forced air cooled 4CX250B's and 2C39's in high power RF amplifiers. (400 watts at 433 Mhz and 100 Watts at 1296 Mhz)

Les.
 

spec

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http://www.eleccircuit.com/the-variable-high-voltage-power-supply-0-300v/

Looking at this schematic. I think the output circuit is safer than the last one I built that smoked due to the Zener and the current limiting is nice, but I'm going to guess that this provides no actual regulation due to a lack of feedback to the gate from the output?
Hi DO,

That circuit will not regulate too well but it will give a variable output voltage and the current limiting function (0.18 amps) is widely used and is effective.

A fully regulated supply could be designed using another transistor and Zener diode though.

spec

PS; Q2 is vulnerable and needs a 470 Ohm resistor connected in series with the base connection.
 
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