building vacuum tubes... some questons

[ryuji]

Filiaments are most of the time tungsten, getters are usually barium. older tubes used phosphorus, harder part is getting it flashed onto the glass without it getting eaten up by atmosphere on the way. They put them inside high melting temp containers and then used rf heaters to release it in there after evacuating and sealing the tubes

You can salvage tungsten from light bulbs

[ArtG]

Pete Millet's Technical Books site has a number of volumes available concerning the manufacture of vacuum tubes.
Scroll down to "Vacuum Tube Theory and Circuit Design". The Walter Kohl books are excellent.


Technical books online

[SpreadSpectrum]

I believe one of the books on Pete's site goes through materials of vacuum tubes and why you would use different materials. For example, it explains advantages and disadvantages of carbon coating the anode and materials choices for all tube elements. I just can't remember the name of it. I think it might have been an RCA publication (not RDH).

Edit: Aha! it is "Electron Tube Design," apparently an internal RCA publication.

[TheGimp]

Procedures in Experimental Physics by Strong is another good ref for equipment construction.

Amazon.com: Procedures in Experimental Physics (9780917914560): John Strong: Books

.01 Torr is about all you can expect to get out of cascaded compressors. To get that low they have to be rotary vane compressors and not piston or scroll compressors.

Commercial Roughing pumps can best this.

[smoking-amp]

You could also put a Roots blower in front of the two stage roughing pump. See them surplus sometimes, but usually too big for home/hobby use.

[v4lve lover]

uhhhmmm here we go.

oil difussion pump , coupled to a turbomuleculair pump . NEED to be leak proof

couple of blowtorches .
lot of fine tooling pilers stuff like that . pincer magnyfying glass . stuuf like that
some sort of LATHE would be great to make bulbs .

spot welder , can be made from a microwave transformer and a few peices of solid copper

OHH i almost forgot some kind of oven would be great for heat treating all the parts before closing the bulb . semiconductor vacuum oven would be perfect . BAKE BAKE BAKE YEesss get rid of that oxygen

OHH and some sort of "clean box " for fillament threating .

i suppose your talking DHT ?

il brainstorm what comes to mind next


also . you need a tidy workplace around 50 square meters . gloves need to be worn during any part of the production and stock up on medical alcohol .

[v4lve lover]

this is my materials post


PLATE MATERIAL
workable iron 0.1-0.05 MM CAN be used , hard to outgass not very pretty .
nickel is better probably VERY thin . as close to 99% percent purity you can get the better .

optional are titanium . carbon
sources are : you gona want to have nickel sheet metal in strips of 3/4 CM
* CTR material . if you ever dismanteled a CTR you know the beam guns are made of PURE nickel . you could try and sample a role from a big producer .
* battery weld tabs . are pure nickel 99.9 cheaper than specialized CTR stuf google will help you out .

you gona need to make a die to form the plate . best to have two half size "bracket" halves that are spot welded on the stem in the last stage .

okay you will need to determene the material yourself . what works best for you you can use WAY thicker plate material than some old tubes used , BUT AT A PRICE . will take ages to outgass . higher emission grid dissipation . alowable bulb temprature . plate material and blackening work towards a higher maximum dissipation . thicker plate material will need more heat to deform .

GLASS& DUMET
your going to need glass stems witch fit your exhaust system and glass whit a outside diameter of around 28mm you can blow MUCH bigger bulbs depending on the amount of glass avalable EG wall thickness
and you need dumet whit matching expansion figures .
you also gona need to be able to make a STEM . or "PINCH " where all the wires come out .
teralabs.org is a good website about glasswork .

cathodes ""emitting surface " EDIT barium strontium and calcium need to be in their carbon bound state EG barium carbonate strontium carbonate calcium carbonate . when evacuating the device you flash the heater during pump out before you flash the getter , when flasing tunsten heaters you flash them at a few 100s degrees above normal operating temperature to turn the carbonates into OXIDES you then flash the getter to remove the last traces , then there is the burn in period to get the emission stable .
directly made cathodes can be made by heating barium strontium (calcium) mixes on a (host ) EG cathode / heater wire . needs to be applied in an alcohol / solution and baked onpossibly some kind of bonding agent needs to be used . by passing a current through it the exact solution is unknown to me . you should try to make some sort of tube resembling a diode whit a very exact plate distance to figure out wich mixture gives the best emission .

i know for a fact you can buy strontium and barium carbonate in small quantities for very low cost . i just dont know the purity or the mix it comes in

ive seen pictures of the fullmusic plant and believe they use some kind of electroplating to get the emission layer on the cathode . possibly in a bath whit positive charged liquid whit a negative wire hanging the solution . attracting particles in the process

HEATER WIRE
the emission layer for barium cathodes should have an optimum temp .
i believe that was somewhere in the region of 900 -1300 degrees Celsius
I
heaters for DHT can be either . nickel ribbon EG flattened nickel wire sprayed whit emission coating . for a bigger working surface . most old tubes used this including 2a3 AD1 ect

OR you can go fancy like emission labs does . and use "hard metal fillaments " in other words using tungsten wire . instead of hard to use nickel . this needs some saying .

"TUNGSTEN can sag and will glow hotter than nickel be course of its higher melting point . its harder . but can still sag into your grid ,
so some kind of spring will need to be used ,
tungsten does have a much longer lifespan than nickel . (shouldnt wear out at 1300 degrees ) and has high tensile strength

prolly gona continue tomorrow

[v4lve lover]

grids
grids . can be made from very simple to very complicated . from just a spiral wire to hard metal frames wound whit super thin wire for ultra high gain .
a spiral wire . can be used . or you could make your own tools to make grids . i could give you some ideas . but it would require you to be able to make hight tolerance parts .

mica can be cut pretty easily . if you have smal drills you can produce a lot of mica's in one go . then split the pack of mica . into induvidiual sheets
mica can be bought almost everywhere its in toasters suspending the heating element . you can buy 10 packs of 10x20 mica . on ebay for a few bucks . easy to cut make a few holes for mounting grids and heaters whit a dremel . and cut the mica whit a knife .

most vacuum tube mica was specially threated whit aluminium oxide and a binder to avoid flash overs . thin ceramic could also be a option . harder to work but looks cool .


getters i suggest you read this . Getter Materials

good options for gettering are
* magnesium low temp . can only absorb oxygen
* barium getters
* plates coated whit zirconium powder . wich is sinistered on . 6s19s uses this for active gettering


bases some ebay sellers sel UX4 8 pin octal european side contacts or P you can use silicone to glue the base to the bulb . ive also dug up a mix for the original glue . if you need it . found it on a website discussing the posibility of asbestos in tube bases or the glue that binds the base to the tube . but i think silicone is your best bet for the sake of simplicity .

[ak_47_boy]

Rotary type AC compressors will pull a better vacuum then reciprocating piston type compressors. I would try to find cheap or free not so worn out 1hp-2hp rotary compressor. Diffusion pumps can be made, or bought for a few hundred dollars. I would tap the bottom of the compressor and take the oil for the diffusion pump right from the compressor, put an oil separator on the exhaust of the compressor and run a capillary tube from the oil separator to the intake of the compressor. You can make an oil separator from a copper pipe and brass or stainless wool, or just buy one for $50 or so.

A 2 stage HVAC or lab type vacuum pump might be fine, most go under 20 micron, many close to 1 especially lab pumps. These can be expensive, and be prepared to change the oil very often to ensure the units longevity.

You might also want build an induction heater to keep all the insides glowing dull red during pump down and to flash the getter. I have no idea how to get barium inside.

Also, you cathode must be oxide coated or thoriated. See wikipedia. http://en.wikipedia.org/wiki/Hot_cathode

[jlsem]

5N nickel sheet and wire:

Nickel (Ni) | High Purity Nickel)

3N8 tungsten wire:

Tungsten (W) | High Purity Tungsten)

3N8 molybdenum:

Molybdenum (Mo) | High Purity Molybdenum)

barium:

Barium (Ba) | High Purity Barium)

John