[David Dunlop]

The HOLDERS, Lamp, No. 1 (ZA 4201), is a very common item found on a great variety of Second World War Era Wireless Equipment. To this point in time, the only real variation I had ever run across when dealing with them was the variety of different coloured cover caps they could be equipped with across all the equipment that uses these Holders.

While recently working on my Main Set Receiver, and with subsequent help from Bruce MacMillan and Jacques Fortin, we have realized two versions exist. The difference is quite subtle but can have a profound impact on ones wireless restoration project, if any of the relevant hardware bits go missing.

It would appear the original design of these holders, whenever that was, made use of a 6BA x ½ inch central terminal screw at the back of the Holder, fitted with a chunky looking 6BA hex nut. This hex nut requires a 3/16 inch socket to work with it. At some unknown point, for some unknown reason now, production of these Holders changed such that the central terminal screw became a 4-40 x ½ inch screw with its thinner and wider hex nut which requires a ¼-inch socket to work with it.

It seems unlikely this difference is a result of two different manufacturers running concurrently with one another, only because any available documentation we can find on these Holders is dated up to and including 1944 and it all refers solely to the 6BA version. The 4-40 screw version is likely a later replacement or upgrade. It has no real bearing on the working capability of the Holder, just one’s ability to service it.

I have 6 of these Holders (two each) fitted to my three 52-Set Receivers. Two are 6BA Pattern and the other four are 4-40 Pattern, Two of the receivers have one of each.

Thought I would put this information out there to minimize other people being surprised by this hardware variation down the road.

David