This plastic marketing aid from Mullard was an ebay find. It is made like a two sided slide rule, a device all engineers of the day would be familiar with, showing B9A valves on one side and B8A on the other.
In use the slider would be positioned so that the valve type required was visible in the bottom window. The pin connections when looking at the underside of the base could then be directly read off from the windows by the pin numbers. Interestingly the lower window shows all valves that share a common pin-out configuration.
It is possible to use the aid in reverse and match the pin connections from an unknown valve, obtained by inspection, and then to read off the possible valve types. Whilst this is an unlikely application for this aid it did get me thinking about a modern type finder aid for valves that had lost their markings.
As the museum data is held in a central database it was possible to generate a spreadsheet of every exhibit with pin connection data. As of July 2009 this exceeds 1,800 valve types. Initially the data was checked for accurate adherence to style and the main records updated where appropriate. This data cleaning ensured that a pin connected to, say, cathode plus grid 3 and also the screen was always listed as k,g3,s and not also s,k,g3 etc. By using Microsoft Excel and the build-in AutoFilter tool the spreadsheet can be used to translate observations of pin connections into the possible valve type concerned.
In practice the spreadsheet is fast to use and much more convenient than looking up old data books. This spreadsheet is shown above filtered for Ct8 valves. The SDHC card version of the museum comes with the complete working spreadsheet. As pin information is added to the equivalents section for valves that we have yet to locate specimens for, the spreadsheet will become ever more comprehensive.
The B9A face of the Mullard aid. The actual device is 224 x 51 mm and very difficult to read as the type is so small. Clicking onto the image opens a large image file with an enlarged picture.
The B8A face of the Mullard aid. Again by clicking onto the image a large file opens with an enlarged picture.