1961 Philips TUV 6W

The TUV 6W shown here is a self-ballasted UV discharge lamp introduced by Philips in the early 1950s. The design of this peculiar light source is quite unique and integrates a starting antenna which consists of a graphite-coated glass tube that also carries the lead wire to the electrode opposite to the end cap. In order to facilitate ionization, a buffer gas consisting of a neon-argon Penning mixture is used. Such design ensures reliable discharge ignition with cold electrodes at the 220‒250 V voltage of Europe’s mains circuits. A high-impedance resistor connects the antenna to the electrode closest to the lamp stem, resulting in the initiation of the discharge at the opposite electrode. This nascent discharge then propagates towards the other electrode, guided by graphite-coated glass tube, resulting in the closing of the circuit in less than a millisecond. The current flowing through the main discharge is then limited to 27 mA by a ballasting resistor located in the E27 end cap.



During operation the electrical discharge presents a peculiar bi-color aspect which arises from different electron energies at the electrodes and between them. The main plasma volume, i.e., the positive column of the discharge, is characterized by a relatively low mean electron energy of around 1 eV which results in mercury being predominantly excited, thus causing the emission of the element’s characteristics greenish blue light color. At the electrodes, the energy of electrons at the cathode side is considerably higher, which causes the preferential excitation of the neon buffer, whose characteristic red light color is emitted from the negative glow. Because of its operation on alternating current, two red negative glows appear to exist simultaneously as a result of retinal persistence.

The TUV 6W bulb is made of a soft glass material with a very low iron content for an optimal transmission of mercury’s shortwave radiations, especially at the resonant 184.5 and 253.7 nm transitions of the element. With such a design and construction, Philips offered a compact and easy-to-use source of UV-C light for general disinfection and sterilization purposes. Later, during the 1970s, the lamp became also useful for resetting EPROM devices. The Dutch produced this lamp until the mid-1990s, when they sold off some of their special lighting business to Cathodeon, which continued the production of this lamp along others.