Surprising AZ1

Surprise contents are usually expected (at least in Italy) inside easter eggs, not in tube boxes but... there are exceptions. The tube described in this note had been acquired more than 20 years ago in an electronics shop and then forgotten inside a drawer; it was inside the original manufacturer (Philips) box that reported the code of the tube that was assumed to be inside (AZ1). The box has been opened only recently in order to use the tube; its content is shown in the picture and, obviously, despite the “Philips AZ1” marking also on the glass, it is a completely different single plate rectifier endowed with a different base (B3 instead of P). It is also possible to exclude any  homonymy due to  the coding system used by Philips before 1934 since it allowed only a single initial letter (e.g. E443H).

The tube looks as produced by Philips in the 30s since it bears the lead seal used in Italy in that period to certify the payment of  the heavy taxes applied to tubes (6 Italian Lire, approximately equivalent to 6 Euro). Looking at this seal we can see on one side the royal symbol  flanked by two lictor fasces and on the other the writing “Direzione Generale Tasse Affari” that was a short notation for “Direzione Generale Tasse e Imposte Indirette sugli Affari”, a tax collecting structure active from 1901 to 1958. After this small historical excursus, the obvious question: which tube has been erroneously marked as AZ1 by its producer? Possible candidates could be, for instance, the 1802, 1803 and 1810 types.  A check at the current absorbed by its filament at 4V indicated approximately 0.6A so that the tube could, in fact, be a 1803.

To thank the Author because you find the post helpful or well done.

Hello Roberto,

this is an interesting find! I fully agree with you, if the heater current is 0.6A, it could only be a 1803. It also has the same look, and even its Telefunken equivalent, the RGN564  looks just the same.

This is not the only Philips rectifier tube with wrong designation known to us.

Philips also managed to mark a big powerful rectifier AZ4 as the small Rimlock AZ41, see under «AZ4 und AZ41 Fehlstempelung von Röhren bei Philips»

Best Regards, Jacob

To thank the Author because you find the post helpful or well done.