WHAT'S INSIDE A VALVE? (i)

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 valve is typical of those which have PINCH consttruction.  The EL37 valve has an OCTAL BASE and you can clearly see the glass PINCH upon which the ELECTRODE CAGE is mounted then secured between MICA plates.   We will go on to discuss each of the components mentioned and highlit in upper case text in future articles but for now, just enjoy this scintillating picture of an undressed EL37!