![]() Note that tubes of same pattern and even same base may not be equivalent. There is no apparent difference between a DM70 and DM71 except the DM71 has short pins for a socket and the DM70 is wire-ended.Īny of the tubes can be looked up on the tube database and Members can see which models of Radio, Tape recorder or Test instrument used them. Grundig portable reel to reel tape using DM71 for recording level Wega battery Table Radio using DM70 as tuning indicator The DM21 is older Octal 1.5V “Magic Eye” The DM70/DM71 is probably the smallest Magic Eye ever made (the DM160 is a VFD annuniciator and not a "magic eye" at all) The pattern is an glowing green exclamation mark about 3/4" high. The filament is for 1.5 volts and HT 45v to 90v. The 1952 DM70 (CV2980, 1M3) (wire ends) and DM71, (1N3, 1M1, Y25) (wire pins) are developed for valve battery radios. The 6AD6/6AF6s give bright displays but require control-electrode voltages of more than 50 volts, as they do not have internal driver triodes. ![]() Note that most of the miniature EMxxxs are side-view, while all the pre-1950s types are viewed from the end. The brightest are probably the EM84, EM87, 6AF6 and 6AD6. This makes the bars quite small but makes the package smaller The EAM86 are relatedto EM84s, except the bars are horizontal to the base (wrapping around the tube barrel partly), rather than vertical. Two on top, side by side, with a double-wide third bar below.ĮM84, EM87(Radio sets mounted vertically or horizontally) Its display pattern was square, not round, divided into three rectangular bar-graph indicators. With AC supply a voltage doubler of two capacitors and two 1N4007 will power it from 6.3VĪnother still available “Magic Eye” is the 6AL7. There may be NOS surplus 1629s still available. It has a 6E5 design, with a target plus a driver triode, and it must be connected a bit differently from the others. Its base is octal,and it has a 12.6 volt heater rather than the usual 6.3v heater. The 1629 is commonly found in WWII military equipment. Here is an article on the 6AF6G explaining how to use the independent patterns. This was useful for things such as FM radios where one side might show signal strength and the other would show multipath. They have TWO control grids, each controlling the opening angle of its own dark wedge independently of the other. ![]() They are not at all like the 6E5 types as they have two separate areas and no internal triode. The 1629 was a common WWII 12.6V version of the 6E6 type.Ī similar round pattern is found in the types 6AD6, 6AF6 and 6AFG. But note that this is NOT a rule, the G and T suffixes can be for other reasons entirely. Thus a 6U5 is straight sides 6 pin and 6U5G is Octal and if a Bulb octal version exists (it would be like a Y63) it might be marked 6U5GT. Often a "G" suffix means an octal version of a 6 pin type and a "T" suffice a Bulb sided version rather than straight tube. The rare 6T5, introduced by Arcturus and Sylvania in 1937, has an annular ring shadow around its center, rather than the conventional angle shadow. The 6AB5 and 6N5 were intended for battery radios, having lower filament consumption. The 6E5 uses a plain triode, while the 6G5 has a variable-mu triode to let it handle larger voltage swings. The "magic eye" has an amplifying triode, which is used to increase the sensitivity of the eye. Some "end view" Magic eyes had side contacts instead of pins. The 6E5 was introduced by RCA in 1935, The 6U5G is Octal version of 6 pin 6UG, very like a Y63, Some models were made not only in 6 pin and 8 pin versions but also in straight and bulb sided glass. All have similar characteristics and use the same 6-pin base, except the 2E5 has 2.5 volt heater. The original types are the 6E5 family in 1934, Domestic radios from 1935. More complex Tuning meters for FM Radio with Stereo Indicator.Peak level or Null indicator on test equipment maybe even up to 1970.Peak level or Null indicator on Direction finders.Tuning Indicator on Domestic and Military radio receivers.It really is mounted at right angles to the normal radio usage. The Animation is of Y63 as mounted in a Greyshaw Instruments CR Bridge test meter when a leaky capacitor is connected of about 15 M Ohms. Now when Magic Eyes are expensive and moving coil meters are cheap, it's hard to realise that in 1930s to 1960s the valve was far cheaper! The moving coil meter was too expensive. ![]() The original use was in 1930s to help people tune radio sets more accurately. ![]() Applications of "Magic Eyes" also known as "Tuning indicators", "Magisches Auge" and "Cat's Eyes" ![]()
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