The sound mixer we are currently using in Project Vivat is a portable mixer (type BD510) and not the one that would have been fitted. It’s much simpler than the correct one but it’s all that we had to hand.
A better match is the Mobile Sound Control Equipment BD580 which consists of the Control Console BD579A and accompanying Mobile Power Supply Unit BD592 and Mobile Amplifier Unit BD591, as seen here in the Marconi Catalogue and also in pictures and drawings of the interior of typical vehicles.
The Science Museum have part of the control console, a photograph of which can be seen on the web page for their collection entry: marconi-sound-mixer-type-bd579a.
Recently there was a listing on eBay for something described as Marconi Wireless Telegraph Control Panel Console Echo Machine BUILT IN ASH TRAY (!) which was actually for the Control Panel BD579A – just what we need!
Bidding was brisk at first but then petered out and we won it for a reasonable amount.
Here are some pictures of the unit as received, it’s a bit rusty and battered, and has been modified with extra Echo Gain controls, but it’s basically intact. It only requires 12 volts power for the illumination, as the amplifiers were located elsewhere, but with a smattering of modern circuitry it can be made to work again!