THE GREAT MULLARD MAGIC BLOG — CRT

Now here’s something you don’t see every day – it’s a Monoscope. These were invented in the immediate post war period in the GEC laboratories at Wembley following on from the need for broadcasters to derive a signal with which to test their equipment. Within the cathode ray tube (CRT) of the monoscope, a solid silver plate, photo etched, curiously using photo sensitive fish glue (yes, really!) and carbon coated depicted the information that had to be produced – in the case of this device, the redoubtable BBC Test Card C.  A signal was generated as a focused beam of...

Mullard used a few dodges to ensure that blemished face plates were not used in tube manufacture such as when fitting the EHT connection in the cone of the 12 inch tube, this would always be located immediately above the gather or shear marks so that when the tube was fitted in the set, the tube mask would hide these marks - pretty clever. Otherwise, it was a matter of 100% inspection and selection and this is how it was done.   Firstly, only blemishes which could be seen from a distance of  3 feet 6 inches distance either under...

Today, let's look at the process for tube screen (or faceplate) manufacture that was employed by Mullard in the early 1950s.   If we had visited Mullard's tube manufacturing area we would have seen a tank holding 250 tons of molten glass and nearby, a work bench holding moulds which were contoured to match the required screen shape.   Glass blowers working in this area armed with iron rods, topped with a ball of fire clay would dip their implement into the molten glass tank and withdraw a bolus of molten glass known as a 'gather'.    The 'gather' would be held...

I had to laugh as I heard a member of the 'flat earth radio amateur society' chuffing on about dead pixels and the lamentable quality of modern OLED screens "Eeeeh, this never 'appened in t'olden days and the picture is no better either" he bemoaned.  I suppose in some ways he was right, after all, CRT screens didn't have pixels but we did have phosophor burns which were even more unsightly and we certainly had face blemishes.    Moving on to picture quality though, if our Samsung LED TV is anything to go by,  I have never ever seen a picture...

You know, this could be me, in my Rosebank school uniform, peaked cap, short trousers, sturdy satchel and a pair of Clarks shoes with a compass in the heel - happy days.... but it isn't. The little lad you see in this 1953 picture is the 5 year old  Norman Skentlebury at the Earl's Court Radio Show of that year.  He appears clutching a typical CRT of the era whilst being dwarfed by the giant model television tube on Mullard's stand because chaps, as we know, size is everything.