Strange Valve Circuit - Redrawn for Clarity

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** This absurd schem was posted here a couple of years back.

The best guess was that it is some kind of lunatic, pseudo medical device.

Might be used by schizophrenics to detect thought waves that are controlling their brains.

** You cannot tell anything.

YOU are just another PITA damn TROLL.

Piss off.

..... Phil

FET's?

The tubes are connected in series for gain.

It looks like the tubes are pentodes, such as 6AU6 or similar.

The wire connecting the suppressor grids together should not be there. Each suppressor grid should connect to its own cathode to avoid unwanted feedback. See

The voltage gain will be quite high. Microphonics and noise in the first stage will render the amplifier useless.

mmfd means micro-micro farads, or 1e-6*1e-6 = 1e-12 = picofarads. 0.003mmfd is wrong. There is no way to get such a low capacitance in a handwired circuit. It should be 0.003mf, or 0.003uF, which is 3 nanofarads. The amplifier is intended for fairly high frequencies, perhaps in the high sonic or ultrasonic region. For example, the reactance of a 3nF cap at

10KHz is around 5kohms.

Input wires of 60 inches will be very effective antennas for all kinds of noise, such as switching regulators, flourescent lights, power supplies, displays, LED lights and all the modern conveniences. These will wipe out the circuit.

For a better circuit, find out what the system is doing and what signals you need to work with. Perhaps a single op amp could do the job.

I forgot to mention the sceen grids need to be bypassed to ground. See above.

s?

Large gain, but probably only at audio freqs (fast rolloff.) Impossible to analyze with a schematic alone: what was the enclosure? The labels, etc.? Was it part of ham radio equipment? Any plate with a manufacturer name?

Provide photos?

Note that the grid input goes to an older earth-ground symbol (square burie d plate, radio transmitter ground.)

Labels seem to read: 60" or less copper cond. covered with non-kink

What's "non-kink?" Some sort of insulation braid?

Perhaps it's a "proximity detector," where the oscillator's plate current c hanges whenever objects move around the antenna. The 100uA cathode meter m ight actually be a "meter relay" to detect when an intruder's body starts/s tops the oscillation.

If not, then the circuit has no output.

If this device is supposed to do something secret and mysterious, then the first rule always is this: DON'T MAKE CHANGES. You must not "improve" i t. Put your ego away on the back burner. Instead, get the original device working. Going to fets or op amps might completely alter the desired ope ration. First, get the original device working, with no changes or improv ements. That way you have a working model to probe, and only then can sta rt duplicating it's behavior using modern devices.

If it's the John Cambpell 1956 "eloptic radiation" device, the Hieronymus machine, then you're supposed to put a photo of your farm on the metal plate, tune the plastic prisms, and all the caterpillars eating your corn crop will be turned into liquid. Later he found that if he forgot to plug in the power, the device still worked. Even later: the tube-amp could be replaced with a paper schematic of a tube amp, but it only works if you draw a battery symbol, to act as a power supply.

I don't have a farm, though. Would it work for like, making hot chicks appear on my doorstep from time to time? Would I have to switch to different kind of pentode or something

They're pentagrids not pentodes. Very different animals.

NT

His first post labelled the tubes as 6AC7s which are pentodes. His schematic also shows them as pentodes. Even the 6AU6 is a pentode. They are not pentagrids since they do not have 5 grids.

They're not pentodes, too many grids.

NT

Pentode refers refers to 5 elements in the tube. That would be cathode,

3 grids, and plate. PentaGRID refers to the number of grids only.

Google is your friend.

It will do that without any modification. Only thing is, you have to stand on one leg, pinch your nose and sing the Hallelujah Chorus. Otherwise the chicks will turn into werewolves and eat you.

NT

The tubes *are* pentodes, no question about it. Yes, even if the coupling caps are .003uF, the low frequency cutoff is too high for audio.

The wire length at the input side is given as 6.0", so the 60" at the output side might simply be a drawing error.

No PS filter cap, no interstage decoupling. The overall gain will be very high above a kHz or so until the Miller effect and stray couplings take over. It's certain to oscillate without some expert shielding.

Count the number of grids in the hexode. Hexode means 8 elements. Pentode means 5 elements. PentaGRID refers to the number of grids in a hexode.

You either can't understand what you are reading (if you actually do) or you are as stubborn as a fence post.

Look at the Pentagrid section in the link you posted and note that on the first line it says "pentagrid or heptode (seven-electrode)". Then what does it show about the Pentode?

Now *read* both sections slowly for understanding. See if you can discern the difference. It is spelled out for you.

Maybe on your planet "hex" => 8, but on this one "hex" == 6.

Looked in a mirror lately? I suppose they're all broken.

Hex is latin for six. A hexode valve has anode, cathode & 4 grids, as the original circuit diagram shows. These are therefore hexodes. I'm grateful to be stubborn.

However the 6AC7 is a pentode - the valves drawn do not match the descriptor '6AC7'.

The circuit appears to be a wacky amplifier that I expect oscillates. What use it might be is still a mystery.

NT

The original drawing shows 3 grids. This is clearly indicated in the first tube. The schematic is drawn so poorly that the internal connection to the anode is missing in the other tubes, making it look as if they have a fourth grid. If that's g4 then there'd be no anode. That missing connection was either carelessly left out or faded and lost in digitization.

Eh you're right. That rules out a lot.