THE GREAT MULLARD MAGIC BLOG — PINCH

WHAT'S INSIDE A VALVE? (iii)

Posted by STEVE M on

WHAT'S INSIDE A VALVE? (iii)

Let's look at the PINCH today.  The PINCH is something borrowed from incandescent lamp manufacture and is where lead-in wires pass through a valve envelope in a cleverly wedge shaped piece of glass which not only provides a perfect impermeable seal but also provides a very nice mount upon which an ELECTRODE CAGE can sit. As can be seen from the photo sequence below,  as we work from A to C, in A you can see the sectioned PINCH at the base of the envelope showing clearly the transit of the wires through the impermeable glass seal.    In B we...

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