The 6U5/6E5 tube was one of the most commonly used magic eye tubes, it was most often used as a signal strength indicator in 1940s and 1950s consumer radios. Indicator tubes with round displays were somtimes referred to as "gooney eyes". The 6U5/6E5 is mounted in an antique 6 pin tube base and uses 6.3V for the filament.
The 1629/VT138 is electrically similar to the 6U5/6E5 although it is mounted in an octal tube base and uses 12.6V for the filament. The 1629/VT138 was mass-produced for use in WWII command sets and other military radio gear, it was widely available after the war as surplus and was used in numerous Heathkit devices and home-brewed ham radio equipment.
Indicator tube parts that begin with 2 and 6 are usually American consumer types. Indicator tube parts with four-digit numbers or that begin with VT are American military types. Indicator tube parts that start with AM, EM, EAM, and EFM are Euopean types. Russia also produced numerous indicator tubes, they are often named with Cyrillic letters. Japan also produced indicator tubes such as the miniature 6M-E5 and the 6G-E12A square-display tube that was used in Quadraphonic stereos.
Unlike mechanical meters, fluorescent indicator tubes are extremely fast devices, they can display signals up to many megahertz. An interesting project would be to make a crude audio frequency oscilloscope by viewing a bar-type indicator tube through a spinning mirror.
Both the EM83, EMM801 and 6AL7 tubes are dual-bar displays that would be well suited for use as a stereo volume meter or for a SWR meter display. The EM84/6FG6 and EM87/6HU6 are fairly common single channel tubes in a miniature 9 pin base, they were originally used as a tuning indicator in radios and as a recording level meter in tape recorders. The EM80/6BR5 is packaged in a miniature 9 pin base and has an unusual fan-shaped display.
Some rare types of eye tubes include the miniature 6355, 6977/DM160 and R2164 tubes and special 6U5/6E5 tubes with a red lamp crystal over the center filament. Used as a radio tuning indicator, the combination 6AD6 eye tube and 6AE6 dual-plate triode control tube was designed so that one side of the eye tube was sensitive to weak signals and the other side was sensitive to strong signals.
|Type||Display||Side View||Pinout (bottom)||Circuit|
|Toyo 6G-E12A||Other 6G-E12A||NU R2164||NU 6355||TungSol 8569|
|General Electric||EZ-6E5D||Svetlana 6E5G||yellow-green 6E5||RCA Match Book||RCA Match Book|
Type, Display, Socket 2E5 top circle, 6 pin, ST bulb, 2.5V 6355 top split circle, 7 pin 6AB5/6N5 top circle, 6 pin, lower drive voltage than 6E5 6AD6 top split circle, octal 6AF6/CV-847 top split circle, short octal 6AL7 top double rectangle, octal 6CD7 top split circle, dual sensitivity, octal 6E5/6G5/6U5/VT-215/VT-198 top circle, 6 pin, ST bulb or cylinder 6E5C/6E5S/6U5G top circle, octal, cylinder 6G-E12A top 2 channel split-square, octal 6H5 top circle, 6 pin, variation on the 6G5 6R-E13 side split bar, 9 pin 6S5 top circle, 6 pin, ST bulb 6T5 top expanding circle, 6 pin 6X6G top circle, octal version of 6S5, ST bulb 12Z-E8 Toyo brand version of 6U5/6E5 JAN-CRC-1629/VT-138 top circle, octal, 12V NU6355 top circle, 7 pin DM70/1M3 side exclamation point, wire pins DM160/6977/IV-15/CV5412 side lit grid, mini, wire pins E82M/5624 side rectangle, dual control, 9 pin EAM86/6GX8 side horizontal split bar and on/off, 9 pin EFM11 top circle, octal EM1 top 4 part circle, octal EM2/6E12 top split circle EM3 top 4 part clover EM4/CV1434 top 2 part circle, 8 pin EM11 top 4 part circle, octal EM34/6AF7/6CD7/6M2 top circle, octal EM35 top 4 part circle, octal EM71 top half circle, locktal EM72 top half circle, locktal EM80/6BR5/6E1P side fan, 9 pin EM81/6DA5 side fan, 9 pin EM83 side double bar, 9 pin EM84/6FG6/6E3P side split bar, 9 pin EM85/6DH7/6DU6 side fan, 9 pin EM87/6HU6 side split bar, 9 pin EM800 side bar, 9 pin EM840 side split bar, 9 pin EMM801 side double bar, 9 pin EMM803 side split bar with pilot indicator, 9 pin HM71 top half circle, locktal? HM85/12DH7 side fan, 9 pin, 12V ME41 top circle, octal PM84/9FG6 side split bar, 9 pin, 9V R2164 top split circle, 7 pin UM80/19BR5 side fan, 9 pin, 19V UM84/12FG6 side split bar, 9 pin, 12V UM85/19DH7 side fan, 9 pin, 19V Y61 top circle, octal, cylinder bulb Y63 top circle, octal, ST bulb Y65/CV51 top circle, octal, ST bulb C/EM2 top circle, octal
Back to FC's Electronic Circuits page.