UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - How CRT re-gun was done

Vintage Engr · 11th Nov 2017, 4:47 pm

Hydroflouric acid, now that brings back even more memories. There was an article in one of the '60s electronics magazines about missing type numbers on valves & crt's.
The idea was that you worked out what the valve was, either by recognising the electrode structure, or from the base code, & then etched the number into the envelope. Prior to the actual etching, one was supposed to melt candle wax on to the surface of the valve/tube, & then scratch the number through the wax resist, & gently brush the acid into the 'stencil'

They did warn you to store the acid (which you purchased from your local chemist) in a polyethelene container. That was the H&S bit!

David.

11th Nov 2017, 4:47 pm	#13
Vintage Engr Heptode Join Date: Jan 2008 Location: Shrewsbury, Shropshire, UK. Posts: 841	Re: How CRT re-gun was done Hydroflouric acid, now that brings back even more memories. There was an article in one of the '60s electronics magazines about missing type numbers on valves & crt's. The idea was that you worked out what the valve was, either by recognising the electrode structure, or from the base code, & then etched the number into the envelope. Prior to the actual etching, one was supposed to melt candle wax on to the surface of the valve/tube, & then scratch the number through the wax resist, & gently brush the acid into the 'stencil' They did warn you to store the acid (which you purchased from your local chemist) in a polyethelene container. That was the H&S bit! David.