Electron Vacuum Tubes

It's likely a shielding material, possibly Aquadag, or a Graphite?  lead? compound. If I find out I will let you know.

 I do have a very few metal shields for those pencil tubes also here somewhere.

 They made sprayed on shield tubes. Hard to find now, but it eliminated the cost of the mfgr. having to make tube shields.
IIRC Majestic and a number of European makers used the spray shielded tubes.

Mostly those type tubes were used in proximity fuses, Radiosonds, and in the old Motorola "Lug A Talkies". There was a type 5642 that was a HV rectifier used in TV sets and oscilliscopes also; plus some very high end receivers and military odds & ends.

FrankB wrote:

Actually they did make a 1 pin tube. I saw one time.
The other connection was the aquadag coating on the outside of it.


( Its all in the elections, protections, and morons.)   

I have a few Pencil Tubes that have a silvery Grey coating do you know what the coating is? aquadag?

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That film really shows just how difficult it is to make a tube.
Lots of repetitive hand work. Probably as boring as heck too, with lots of repetitive motion injuries to the hands and wrists.
 The engineers who made the automated machines really had a challenge in their design.

OK try it now.

Cliff,
 "Watch this video on YouTube.
Playback on other websites has been disabled by the video owner."


This is the message that comes up when you try to watch this with the link on your site.
Thought you might want to know.

Heres a Video of How Mullard tubes are Manufactured on the Assembly Line, Its about a 30 minute presentation. I will say it really took geniuses to design the automated machinery.

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Electron Tube 6AK5 Filament changes resistance over time
----------------
In Communication Equipment Maintenance Bulletin  November 1945 Supplement No. 5 section II

"REPLACEMENT OF 6AK5 TUBES IN THE
AN/ARC-1
The Filaments of 6AK5 tubes leave the unusual
Characteristic of decreasing in resistance with
usage. Consequently if a tube is being replaced
in an AN/ARC-1 equipment which has been in
use for a some time, it will also be necessary to
replace the tube whose filament is in series with
the filament of the bad tube. The   second tube
can be determined by referring to the schematic
diagram in the handbook of maintenance instructions
or merely by removing the bad tube from its socket
with the equipment turned on and noticing what other
6AK5 tube darkens.
The latter method is assuming, of course, that
the   filament of the bad tube is not   burned out.    
If it is burned out, another 6AK5 will already
be dark.
If the 6AK5 tubes are not replaced in pairs
the tube with the most. Operating time will have
lower filament resistance and cause excessive
filament voltage to appear across the new tube
with consequent failure."

Actually they did make a 1 pin tube. I saw one time.
The other connection was the aquadag coating on the outside of it.


( Its all in the elections, protections, and morons.)   

As an added note for shielding:
I have been seeing a lot of old radio tubes using Goat and straight shields that have an item like a solder lug slid over 1 pin and it protrudes up into the shield to make contact, thereby grounding the shield to the chassis.

Its a similar way to ground the shield like attaching a piece of tinned braid to the tube shield and chassis with solder. (This was done in several of the old Tv and radio sets I have worked on. It apparently saved the mfg from having to buy the tube socket with the bayonet locking shield. A piece of tinned braid or stranded wire is cheaper than a special socket.

Boy its been a while since your posting, before I read it.  

The Flasher tube is used to make the neon tube excite when a signal of strength is reached and acts as a tuning indicator. It is connected to the AVC tube which makes sense.

The term Transl. Refers to the Mixer tube (Translates or mixes the RF and IF oscillator signals together) then the IF transformers separate (filter out the smaller RF signal that was imposed) .

That's My idea anyway.

I'm looking at the schematic diagram (Rider Sears 5-9) for Silvertone models 1722 and 1732. One of the tubes, a 6B7, is indicated "flasher." What does this mean? What would be a more common description (radio dates to 1934)? I've never seen such an indicated function before.

This schematic diagram is so old--although relatively recent in 1934--that it does not have circles around the tubes, only showing the tube elements! It also indicates, curiously, a 78 as "Transl.," which, according to its place in the diagram, must mean mixer or converter. Whatever, difficult to read. An 85 is indicated "Det - 1st Audio" but not also AVC, although strangely it shows two diodes, but the AVC function is provided for in ANOTHER 6B7! Confusing, huh? I may be getting this unit for repair/restoration soon; please wish me good luck. In the 1934 Sears radio mail order catalog, these two models are Sears's most expensive--$84.95 for the 1732, $89.95 for the 1722 (the five dollar difference seems mainly related to the cabinets).

This should be helpful for those wanting to know.
Commercial tube markings could come off in an instant, to be relabeled and resell, however Military tubes because of specifications had to have permanent markings.
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MIL spec = MIL-PRF-1L
b. PERMANENT- MARKING: The information specified in 3.5.a shall be applied such as grit blasting, etching, baked enamel silk screening, permanent adhesive decals or labels,
or any other method that will assure permanence equal to these methods of marking. The marking shall be permanent to the degree that the removal of the information can only be accomplished by deliberate mutilation of the marking, or destruction of the tube.

c. Secondary marking requirements: Required information, other than specified in 3.5a shall be marked on the tube by any method that will ensure legibility after prolong use of the tube.
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My comment
Also the tubes will either have a "J" or "JAN" Immediately before or after the number the part number or if the part is too small then "J" below the part number or if a hardship on the manufacturer..
Also at one time the letter M was approved but then rescinded. Also a requirement of the manufacturers designating symbol (Cage code) was required.
---------------------------------------------
additional markings:
W Ruggedized, or military grade
WA,WB Improved, backward compatible military/industrial variants

"I assume you grounded the foil to the grounding tab that contacts the spray shield on the tube."

(1) Yes, as clearly stated in my original post, I grounded the foil.

(2) No, the tube did not have a spray shield. It was an ordinary 58, which is why I needed a goat, or other, shield

I thought both of these points I had made clear by statement or obvious implication in my original post!

So with all of the above being said....
Why couldn't one put Dag coating on the tube?
Its conductive and sure should shield the tube.
Might be an interesting experiment.

I just can't fathom why the foil failed to work, unless something to do with the capacitance, killing the tubes function. (But a spray on shield s h o u l d have had the same effect- killing the signal.)
I assume you grounded the foil to the grounding tab that contacts the spray shield on the tube. If not, I can see why it might have not worked.

I wonder what a shield made of lead sheet or pipe would have done?
That was commonly used in some TV tuners.

I am wondering why He said that you needed a external shield, unless it was for audio howling. But was it used in the audio stage or RF/IF section?

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Having looked in several different data sheets, the 58 is constructed with an internal shield connected to the cathode and within the tube.
I saw no reference to a 58S designation as such, but most did mention the internal shield.

That's good to know, but I am now curious as to why it wouldn't work with the external shield (aluminum foil method) you tried, unless it upset the interelectrode capacitance? I am also curious about the sprayed tube mentioned.
Just wanting to know. Thanks.
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I did find additional info on sprayed tubes from Wikipedia. Learned something today
"....Shielded tubes for Majestic radios[edit]

In the early 1930s, the Grigsby-Grunow Company—makers of Majestic brand radios—introduced the first American-made tubes to incorporate metal shields. These tubes had metal particles sprayed onto the glass envelope, copying a design common to European tubes of the time. Early types were shielded versions of tube types already in use. (The shield was connected to the cathode.) The Majestic numbers of these tube types, which are usually etched on the tube's base, have a "G" prefix (for Grigsby-Grunow) and an "S" suffix (for shielded). Later types incorporated an extra pin in the base so that the shield could be connected directly to the chassis.

Replacement versions from other manufacturers, such as Sylvania or General Electric, tend to incorporate the less expensive, form-fitting Goat brand shields that are cemented to the glass envelope.

Grigsby-Grunow did not shield rectifier tubes (except for type 6Y5 listed below) or power output tubes.
Early types based on existing tubes. (Non-shielded versions may be used, but add-on shielding is recommended.) G-2A7-S Pentagrid converter
G-2B7-S Semiremote cutoff pentode, dual detector diode
G-6A7-S Pentagrid converter
G-6B7-S Semiremote cutoff pentode, dual detector diode
G-6F7-S Remote cutoff pentode, medium-mu triode
G-25-S Medium-mu triode, dual detector diode for 2.0 volt storage battery radios. Glass type 1B5/25S used for replacement.
G-51-S Remote cutoff tetrode
G-55-S Medium-mu triode, dual detector diode
G-56-S Medium-mu triode
G-56A-S Medium-mu triode, original version of type 76, but with 400 milliampere heater. (Not to be confused with types 56 or G-56-S, which has a 2.5 volt, 1.0 ampere heater.)
G-57-S Sharp cutoff pentode
G-57A-S Sharp-cutoff pentode, original version of type 6C6, but with 400 milliampere heater. (Not to be confused with types 57 or G-57-S, which has a 2.5 volt, 1.0 ampere heater.)
G-58-S Remote cutoff pentode
G-58A-S Remote-cutoff pentode, original version of type 6D6, but with 400 milliampere heater. (Not to be confused with types 58 or G-58-S, which has a 2.5 volt, 1.0 ampere heater.)
G-85-S Similar to G-55-S, but with 6.3 volt heater.

Later types 6C7 Medium-mu triode, dual detector diode, similar to later octal types 6R7 and 6SR7. Seven pin base. (Shield to pin 3.)
6D7 Sharp cutoff pentode, identical to type 6C6, but with 7-pin base. (Shield to pin 5.)
6E7 Remote cutoff pentode, identical to type 6D6, but with 7-pin base. (Shield to pin 5.)
6Y5 Dual rectifier diode, similar to type 84/6Z4, but with 6-pin base. (Shield to pin 2.)

Other tubes unique to Majestic radios G-2-S and G-4-S Dual detector diodes with common cathodes. The first detector diodes packaged in a separate tube. Forerunners of octal type 6H6. Spray-shielded. Both tubes have 2.5 volt heaters. G-2-S is larger and has a 1.75 ampere heater. Type G-4-S has a 1.0 ampere heater. Later Sylvania replacement type 2S/4S has a 1.35 ampere heater.
2Z2/G-84 Half-wave rectifier diode with 2.5 volt indirectly heated cathode. A lower-voltage version of type 81. Not interchangeable with type 6Z4/84.
6Z5 Full-wave rectifier, similar to types 6Z4/84 and 6X5, but with 12.6 volt center-tapped heater......"

There is nothing wrong with either the tube or the receiver. However, it is clear that we have a failure to communicate.

When I purchased the unit the seller told me that I would need a shield for the 58, that the original called for a 58-S, or sprayed tube, not available.

I have a boxful of shields, as I stated, so I didn't worry about a missing shield. But none of my shields would fit the 58.

I remembered a tip somewhere years ago that ordinary kitchen aluminum foil could be used as a tube shield. I tried it and it did not work.

In fact, it stopped the reception I did have with the unshielded 58--feedback and loss of alignment.

A hobby friend supplied me with a correct fitting shield for the 58.

Proper reception was immediately restored.

What I was attempting to report, but apparently failed, is that kitchen aluminum foil does not work as a substitute tube shield.

So, no, I do not need to probe around and the tube does not have a bad connection or a broken grid cap wire, and nothing is wrong with the tube contacts.







[i]

That's funny, only thing I can surmise is that removal and replacement of the tube the first time, tube contacts were still making connections, however the second time you've inserted the tube, it may not have been making correct contact with the pin contacts.
If I were you, I would probe around those pin connections, for the loose joint, or cold solder connection. The next question would be if the tube itself had the bad connection. The other consideration would be a broken wire the end the grid cap, were part of that wire itself. It would be worth checking now rather than later, to avoid the same problem down the road.

Recently I had need for a tube shield for a 58 tube. I happen to have a small boxful of shields but none of them would fit the 58. Then I remembered a thread from several years ago in an antique radio forum. Someone was inquiring where he could obtain a certain tube shield. The first replier kindly gave him a couple of sources where he could try. Then a second reply informed the original poster that all that is necessary to shield any tube is to wrap it in ordinary kitchen aluminum foil. Sure.

We were out of foil here at home, which required a trip to the grocery store to buy a roll. Anxiously trying this reportedly amazingly simple substitution tip, I carefully wrapped the 58, provided for grounding it, and returned it to its place in the chassis, and. . .nothing--no sound.
(Before anyone asks, no, the tube cap was not shorting to the foil.)

E-mailing a good hobby friend with my need for a tube shield, he found one and sent it to me. Problem solved.

Fortunately, we can use the foil, so it didn't get wasted.

I will have to look for that. Good info indeed!

The best tool I've ever used to quickly and ridiculously easily remove loctal tubes from their sockets
cost me a whopping. . .$2.29. It's a tack remover and I bought it at one of my local dollar stores. Slip the forked end under the tube's base at or near the socket rivet and push it down. Voila, the tube is ejected! No wiggling the tube, no rocking it, no cursing.

Click Here--> Tube Manuals

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Click Here --> for tube Manuals more free

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Here's a couple more:
Tony Wells Apprentice 5 +posts
Posts: 8
Join date: 2010-11-22
Age: 51
Location: Tyler, Texas


Click Here-->Frank's Electron Tube Data sheets

Click Here--> Roy J. Tellason's Tube Information

Click Here-->Yet More Tube Data tdsl.duncanamps.com/tubesearch.

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Radio tubes are designed in many different styles.

Miniature-octal-loctal-compactron-novar-acorn-pencil

RF amplifier, IF amplifier, Detector-Mixer-Oscillator-Audio amplifier

Glass, Ceramic,metal

Two-three-four-five-seven-nine pin styles