Radio Panel Lamps - Dial Bulbs
Radio panel or dial bulbs were first used in the USA in 1926-27 when A/C radios were developed. These early lamps were used primarily as "on" or "off" indicators. A range of E10 based bulbs was made by General Electric covering voltages from 2.5 to 6-8. The filament support bead in these was white and the diameter of the bulb was 10 mm. Most of these bulbs located today have age darkening on the exposed part of the base, which obscures the voltage printing. At least four types are known and identified by the physical size of the filament. These are shown on the top row of photo no 1.
Early in the 1930's it was realised that because of the confusion perceived with the white coloured bead, other colours would be needed for identification of different voltages. Also at this time the small bayonet Ba9s became available and was used on panel bulbs and in many automobiles, mainly in dashboard use. General Electric, as leaders in the field, developed a series of type numbers to identify their dial bulbs and these were: 39,40, 40A, 41, 42, 43, 44, 45, 46, 47, 48, 49, 49A, 50, 51, 55, 291, 292, 292A. Most of these are shown in the middle and bottom rows of photo no 1. These bulbs ranged in voltage from 2 to 6.3. It is interesting to note that US radios with 2.5 volt filament circuits are today often found with the original type 41 dial bulb replaced by a standard type 14 flashlight/torch bulb.
All bulbs from type 39 to type 49A, 291,292 and 292A have the T3&1/4 sized tubular bulb and were 30 mm in length. The 50 and 51 had the G3&1/2 diameter bulb. These two types were also available in sprayed red and sprayed green. The 55 had a G4&1/2 diameter bulb. Both the 51 and 55 had non radio use as dashboard instrument panel lights in American vehicles from the mid 1930's to the late 1960's.
Another US made panel bulb of interest is the 28 volt type 313. It had a T3&1/4 diameter bulb and was fitted with a Ba9s base. This bulb was widely used as an instrument light in aircraft and this included radio equipment. In commercial use it was widely used in music band sound systems which were made to operate on 30 volt power systems, usually in conjunction with discarded 30 volt power transformers found in older computers. A suitable resistor needed to be used because of the 2 volt difference.
General Electric was the main manufacturer of these bulbs and before 1945 they were sold with the GE Mazda brand and for export with the GE Edison brand. These two "sub" brand names were discontinued due to an antitrust court case that involved the monopoly of the lamp industry in the US, by GE. In most instances manufacturers sold the bulbs in boxes of 10 - photo no 2 - but National Union had a serviceman's box of multiples of most types.
GE also introduced the NE51 neon indicator bulb around World War Two. It had the T3&1/4 bulb and Ba9s base. It was widely used as a power indicator and to show "shorts" and "gas" in several types of tube tester.
There are 14 known manufacturers in the US of panel bulbs as well as General Electric. The main GE lamp factory was at NELA Park (National Electric Lamp Association) in Cleveland, Ohio. Some other companies made lamps alongside their tube making operations and others only made the standard range of miniature lamps, including panel/dial bulbs. These are: Arcturus Radio Tube co, Chicago Miniature Lamp Co, Eveready (National Carbon Co), Herzog Miniature Lamp Works Inc. (Sol-Rex brand), Hudson Lamp Company, Matchless Lamp and Tube Company, National Union Radio Corp, Philco (Philadelphia Storage Battery Co, Raytheon Manufacturing Co, Sylvania Products Co, Tung Sol Lamp Works, Westinghouse Electric and Manufacturing Co. Wizard brand tubes and bulbs were sold by the Western Auto Supply Co (GE may have made the bulbs).
In the United Kingdom, Associated Electrical Industries (BTH Mazda), Atlas Lamp Works (later Thorn Industries), Lucas/Philips, GEC Osram, Rival Lamp Works and Vitality. In 1987 the Chicago Miniature Lamp Co was acquired by the newly formed VCH International. They also bought Hivac and vitality at the same time. In Australia the Electric Lamp Manufacturers Association began making small lamps at their factory in Clyde, a suburb of Newcastle. This was about 1962. Panel bulbs wre included in the limited range and had the brands Condor (a Philips subsidiary), Mazda (BTH), Osram (GEC) and Philips All these small lamps were discontinued about 1965 because of cheap Asian imports. It appears that the only panel types made were 6.2 and 6.3 volts. Philips with type numbers 8024D/N and 8045D/N have been located.
The Asian situation was quite different. Bulbs were mass produced in China, Hong Kong and Japan, right from the early 1930's. There were several companies in China, including the Hua Ta Lamp Works. Many Chinese lamps simply had the country name stamped on the base. Little has been found on any history of these. The same was true of Hong Kong. In Japan several large companies - around 20 - made panel bulbs. The main ones being the Central Bulb Co, Chiyoda Shooki, Kato Lamp Co, Kitano (Stanley brand), Riken Vacuum Industry, Shinigawa Denki and SK Suzuki. In many instances the country name and voltage was shown on the bulb bases. Asian panel bulbs were also being mass produced in so called "cottage industries". The market was flooded with cheap imports.
The main company making panel bulbs in Germany was Osram GmbH in Berlin. Early Osram panel bulbs were unique in that the filament was a loosely wound coil about 1.5 mm diameter and 4 mm long. It was horizontal to the base and not curved in an inverted "U" as was the norm. One very early Osram panel lamp has been seen with fibre insulation in the base, rather than black glass. The little known Rafa lamp Company made miniature lamps including panel bulbs. These were available in boxes of 100.
From as early as 1930 Philips in Holland made many panel bulbs and other lamps designed for radio use. The type number series for these was 8000 onwards but some have been found in the 7000's. In the early 1930's at least two bulbs were made for radio dials with the Ba15S base. One of these is the 8040. Others of this time (where almost no information exists) were the 8046, 8047, 8048, 8053 and 8054. The American series 40 - 46 (at least) were made in Holland and exported to the US. Also the 8008D, 8008N,8009D and 8009N were direct equivalents of the American 40, 46, 47 and 44. Philips also made Condor brand panel bulbs for export but it is not known what types these were, except that Condor employed the e 7000 series of type numbers for small bulbs.
In Russia the Moscow Lamp Works made panel bulbs but details of these and other manufacturers is not known. Similarly the Tungsram Company made a decent range of these bulbs. Other European countries had factories making them but also details are not known.
Radios were made with one panel or dial bulb, up to some large radios using eight bulbs to light the dial. In some instances multi band radios had separate circuits for panel bulbs so they could be switched on according to the band wave section of the panel.
With the advent of transistor radios and other developments, use of smaller bulbs became necessary and most manufacturers changed to meet these needs. Small bulbs on wire leads have given way to LED's and older panel bulbs are a thing of the past. A few companies do make replacements of older bulbs but these are mainly Chinese. Photos 3 and 4 show these types.Attachments:
- American panel bulbs 1920's -1970's (71 KB)
- 2 Panel bulb boxes 1930's - 1970's (79 KB)
- 3 Modern panel lamps - Chinese etc (57 KB)
- S4 Sub miniature panel bulbs 1970's - 2000's (55 KB)
A comprehensive listing of U.S. radio bulb models is shown here.