FC's Fluorescent Magic Eye Tubes

(C) G. Forrest Cook 2008-2024


Here is a collection of information on a variety of fluorescent magic eye vacuum tubes, which are also known as indicator tubes. Through the use of controlled electron beams, this type of tube can illuminate a variety of circular and rectangular patterns on a phosphor-coated display element. I started assembling this information while designing my Hammonator guitar amp and Magic Eye Tube Wavemeter projects. The list of tubes has been expanded to include almost every indicator tube that I am aware of. This information is intended to be useful for those who wish to design circuits that use this type of tube. Many of these tubes are available for reasonable prices on eBay, they can also be purchased from vacuum tube surplus dealers.

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 across 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.

Eye Tube Types

Type Display Side View Pinout (bottom) Circuit
6AF6/CV-847 6AF6 6AF6 6AF6 6AF6
6AL7 6AL7 6AL7 6AL7 6AL7
6G-E12A 6GE12A 6GE12A 6GE12A 6GE12A
6CD7 6CD7 6CD7 6CD7 6CD7
6ME5/6M-E5 6ME5 6ME5 6ME5 6ME5
6T5 6T5 6T5 6T5
6U5/6E5 6U5 6U5 6U5 6U5
1629/VT138 1629 1629 1629
DM70/DM71/1M3 DM70 DM70 DM70 DM70
DM160 DM160 DM160 DM160
EAM86/6GX8 EAM86 EAM86 EAM86 EAM86
EM34/6AF7/6CD7 EM34 EM34 EM34 EM34
EM35 EM35 EM35 EM35 EM35
EM71 EM71 EM71 EM71 EM71
EM80/6BR5 EM80 EM80 EM80 EM80
EM83 EM83 EM83 EM83 EM83
EM84/6FG6 EM84 EM84 EM84 EM84
EM85/6DU6 EM85 EM85 EM85 EM85
EM87/6HU6 EM87 EM87 EM87 EM87
EMM801 EMM801 EMM801 EMM801 EMM801

Miscellaneous and Rare Eye Tubes

Toyo 6G-E12A Other 6G-E12A NU R2164 NU 6355 TungSol 8569
6GE12A 6GE12A R2164 NU 6355 TungSol 8569

6U5-6E5 Varieties and More

Ken-Rad RCA Philco Sylvania Zalytron Zenith Internal Structure
Ken-Rad 6U5 RCA 6U5 Philco 6U5 Sylvania 6U5 Zalytron 6U5 Zenith 6U5 6E5 Elements
General Electric EZ-6E5D Svetlana 6E5G yellow-green 6E5 RCA Match Book 1 RCA Match Book 2
GE 6U5 EZ-6E5D Svetlana 6U5 Yellow Green 6E5 RCA Matchbook front RCA Matchbook rear

Fluorescent Tube Types

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
Chart of Eye Tubes


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