Frank's Electron tube Pages
	Unknown Sylvania Tubes	www.tubedata.org www.tubedata.info

can anyone identify these tubes?   (click images for enlargement)   email
diode	thyratron?	pentode
Brand on box: Sylvania code on box: Syl-1068 number of pins: 3 Vf ~ 0.75..1 Volt   See also: drawing	Brand on box: Sylvania code on box: Syl-1168 number of pins: 4 Vf ~ 0.75..1 Volt gas-filled See also: drawing	Brand on box: Sylvania code on box: Syl-1268 number of pins: 5 Vf ~ 0.75..1 Volt Heihth = 25mm, wire length = 40 mm. See also: drawing

Below some of the reactions I received about these tubes: (added 2004-01-23)

2001-07-32 - P.La. (fr): Concerning the miniature tube "wanted", in the middle, I think that it's a subminiature gaz thyratron. The electrode labeled "anode" in the drawing is the control grid, and the unknown rod is the anode. Frank: This was a good suggestion as I did not realize this before.

2003-03-24 - S.Ha.: This is just a wild guess, but the three tubes you show on your web site (Syl-1068, Syl-1168, and Syl-1268) may have been made for use in proximity fuzes (for mortar and artillery shells) during World War II. I have seen a few schematics for these fuzes that were published after they were declassified, probably in the 1960's. The tube types were not identified; there was only a notation that they were no longer available. These fuzes were powered by a small generator driven by a turbine of some kind. These circuits used a triode as an oscillator-detector, a pentode as an amplifier, and a thyratron to fire the explosive charge. Volume 17 of the Radiation Lab Series shows several subminiature tubes made during the war by Sylvania. The later subminiature tubes used a different type of stem with the leads arranged in either a line with a flat press stem or in a circle on a button stem. These tubes appear to be earlier than that. The later tubes were also enclosed in either an oval or round envelope, again of standard dimensions. Your tubes seem to use three different sizes of envelope. The workmanship on the tubes seems very crude. The exhaust seals don't look as consistent as those resulting from automatic machinery. Again, this would imply an early date for the tubes.

2003-07-13 - S.He. (us): I have a few hundred of these I bought in the early 80's. I built some relaxation oscillators for fun and my friends (old) tell me they were probably developed for artillery fuses. I have no concrete data on these but I will let you know if some comes my way.

2004-01-23 - J.La. (uk): Is not possible that these were the valves made by the Americans to implement the proximity fuse design that was taken to America by the Tissard Mission in1940? The British prototype was taken to the U.S.A.along with the magnetron and centimetric radar equipment to benefit from the American manufacturing expertise . This is only a thought but it might suggest an area to investigate.

2004-01-23 - Frank: Thanks for your reactions so far!!! I received many mails with all kind of suggestions: radio tubes, telefhone equipment, etc. In most cases the suggestion was that these tubes were used for proximity fuses during WW2. So I guess that's what they probably were used for. Still, if anyone should find some data for these tubes.... Please let me know!

2004-04-08 - B.Wa. (us): I am attaching pix of tubes I actually removed from battery powered VT fuses and of one of the fuses. a3_gg.jpg (71751 bytes) b1_leads_gg.jpg (67084 bytes) b2_gg.jpg (74619 bytes) b3_gg.jpg (57084 bytes) VT-mk53-comp.jpg (56734 bytes) VT_Mk_53.jpg (61578 bytes) VTparts3.jpg (126432 bytes) VTparts_4.jpg (274398 bytes) shell_fuse.jpg (81773 bytes) See also:JHMs Virtual Valve Museum

2004-08-14 - Al (us): An other sugestion is that the 4 wire tube may be the SN856F. Check out this article from the March 1986 OTB. Here is a note from Jake, author of the SN856F article and a photo. (OTB = The 'Old Timers Bulletin' published by the 'Antique Wireless Association') FrankP: Al, thanks for this addition! However I'm not sure about this as my tube seems to have neon inside. It has an orange glow inside when current flows from either electrode to the filament.

2005-01-23 - Cle (us): Found some info on the construction of rugged valves for proximity fuses. US Patent 3113235 Rugged Vacuum Tube, Henry H. Porter, Sebastian Karrer, Raymond D. Mindlin, James A. Van Allen. Filed Jan 1944, Published Dec 1963. In Ralph B.Baldwins book 'The Deadly Fuze', Dr. Ray Mindlin is credited with much of the valve design especially the "mouse trap" filament. Just dismantled an early MK45 from Springfield Arsenal, three triodes and one thyratron. Construction of the fuse is virtually identical to the MK53. The valves are similar to Fig. 8 in US3113253, whereby the valve base is pressed into a cross shape and the micas are held in place by four vertical rods. Most of the resistors in the amplifier section read high or are open, similarly, a lot of the paper caps read low or are open. The 0.004uF caps "RCA Type M" all read about 0.0044uF with no leakage. However, components in the oscillator section are all OK and the oscillator draws about 3mA at 50V and dips to 1.8mA when you hold your hand near the antenna. Attached a copy US3113235 and US3166015 (Radio Frequency Proximity Fuse) which describes the operation of the fuse, circuit diagram included.

2007-06-06 - Paul (us): The three Sylvania tubes you show are almost certainly the tube used in WWII VT (variable time) antiaircraft fuses, also called proximity fuses. Old fuses simply had a timer that was set to the estimated time required for the projectile to reach the airplane before the projectile was loaded into the gun. VT fuses also had a crude 'radar' built into the fuse. The fuse contained a transmitter that transmitted a continuous signal and a receiver that would detonate the warhead when a strong enough echo of the transmitted signal was received. The gas filled tube is essentially a thyratron and when the received signal was strong enough it would cause the thyratron to fire setting off the charge. After the war these tubes were used in remote controls for model airplanes and cars, presence of a signal from the transmitter would operate the thyratron and activate the control function. Strictly on-off control but it worked. This site describes the VT fuses: http://www.history.navy.mil/faqs/faq96-1.htm