THE GREAT MULLARD MAGIC BLOG — EL37

Continuing our journey to look at what's inside a valve, today we are going to look a little further at our EL37 pentode with the envelope broken open.  After a little more surgery on the ELECTRODE CAGE we can see in the centre. the white vertical cylinder of the CATHODE, surrounding that are the three concentric grids, the inner being the CONTROL GRID, then comes the SCREN GRID and finally the SUPRESSOR GRID. 

I thought I would write a series of blog articles on what is inside a valve.  Famously, the head of Mullard UK, the ex-Philips SS Eriks once stated that the only British thing inside a Mullard valve was the vacuum and after I recently waffled on to some poor chap about electrode cage construction, pinches and getter flashing, they were bemused so I thought that I had better expand on the great Dutch master's scathing comment, so, without further ado, let's talk about......... what's in a valve.................................. The picture below shows a sectioned Mullard EL37 output pentode, as you can see, this...

These were selling like hot cakes in 1951 and details of their build and performance featured in much of the Mullard official literature of the time. Here we see Arnold Polkinhorne doing something with a Philips valve voltmeter.  Just look at that fat bottle EL37 lurking on the chassis as well as a stash of more MHSVT in the background. The fun cotinues as here is Dorothy Prinkle nimbly constructing and lacing a wiring loom for a MHSVT - looks like she's using the silicon covered wire display from Phil Marrison's BVWS stall - haha!