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Homemade Vacuum Tube

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V

v4lve lover

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Joined 2010
smoking-amp said:
My father built some "tubes" long ago

You would need an awfully fine thread attachment for a lathe, I think, to wind grids. Some of the coil winder machines have an infinitely variable cam arrangement for winding pitch, just the thing.
Maybe if the feed gears for the thread attachment on a lathe were changed, could get fine enough pitch. But the grid support rods normally have notches in them for the wire to drop in. Then they get roll crimped to hold the wires.
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yeah . but there are a lot of technical difficulties in making a grid winder .
like how do you get the support rods that straight ? originally they where glowed passing a moderate current through them when they where tensioned .

a machine capable of making grids would be VERY costly .

as there is a lot of fine machinery used . i dont think using a lathe would be any good .
for a draw type all the components must be moving through a series of cogweels . to determine the spacing of the grids .

i thing a draw type winder would be more realistic.
this would mean designing a machine witch has possibly more than a few houndred parts . all custom made

for a draw type all the components must be moving through a series of cogweels . to determine the spacing of the grids .

two parallel copper wires are first glowed . at the end of the machine . a cutter revolves around the wire in close proximity to a jig that keeps the wire from sagging in because of the pressure of the cutter blades
parallel to the cutter is a wire feeder . when the grid is made by feeding in wire in the cut piece of grid . some mechanical guilotine type thing cuts them of the made length .

for each specific grid different length of grids are required . and by that i mean the length between the support rods . this would vary as some types of tubes require heavily stretched grids

finaly i would like to point out that more classical grids for DHT'S are pretty easy to make . you can vary the grid thickness and diameter pretty easy . even on a homemade machine


common dont be shy . this had me occupied for 20 minutes . throw some ideas in !
 
smoking-amp

smoking-amp

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Joined 2001
Why wind a grid at all? I've seen micro-perforated thin stainless steel sheet. Probably was done with a laser. You could see thru the sheet, but the holes were almost invisible. Just cut some pieces out and spot weld it to some rod supports. Probably exceed frame grid gm if you can mount it close enough to the cathode. Probably would have to tension it like the shadow mask in a color TV picture tube. That could of been what it was. I saw a whole box of them in that hi-tech scrap metal yard. They were big enough for 21 inch tubes.
 
smoking-amp

smoking-amp

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Joined 2001
According to "Building Scientific Apparatus", the most desirable alloys for construction of high-vacuum and ultra-high vacuum apparatus are the AISI types 304 and 316. Type 316 has the greatest resistance to heat. Both are high nickel alloys. I would guess that whoever can make the perforated SS sheet could also make Nickel sheet too. It may have to be gold plated for use as grid 1. Won't be cheap.

There is also a plating process that can make a room temperature electron emitter. So no need for a heater. I would just use a ceramic chip holder with layered sheets. The plate would be the heatsink back, the grid would be spaced up by a thin ceramic spacer around the edge, and the cathode spaced up another layer to form the topside. The whole assembly would have pre-silver soldered and fluxed surfaces around the bonding edge, just stack it all up and heat until it all melts and bonds. Guess it would need some evacuation tube somewhere. The terminals would just be extended sheet tabs sticking out the edges like an RF transistor. Mass produce them and sell them for a $1.
 
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V

v4lve lover

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Joined 2010
TheGimp said:
Why not copper for plates?
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copper is indeed a very good material . you would need 0.025cm thickness

copper is readily avalable . it needs some sort of active vacuum getter tho
copper could be used as plates but i guess you would need to carbonize it .

also i think you could make zirconium coated copper for better heat radiation . and active gettering

but why the hel not nickel ? there is a list of company's making nickel 200 99.99 for battery weld tabs . it would be an economical way of accuiring your nickel in strip frorm

also there is atleast 1 company still making nickel strips on role for vacuum tubes
nickel is still better . you could make an special furnace . where you burn small quantity's of oil to blacken the nickel . then it would need to be baked on in a hydrogen furnace

all materials are avalable .

and you ask why make a grid ? becourse you want to recreate old tubes not develop new ?
 
G

George Schmermund

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Joined 2011
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