THE GREAT MULLARD MAGIC BLOG

Today, a question from South Korea - what is the best Mullard input valve for a Leak TL12.1.  Well, you can fit as per original, the EF36 or the improved version, the EF37 or the super improved version the EF37A or the mega special version the ME1400.   The Mullard Type EF36 was designed and introduced to market in 1940 as a general-purpose RF/IF/AF pentode with a non variable mu characteristic.    There were two famous uses for the EF36, firstly, Colossus, Tommy Flower's computer at Bletchley Park used rows n rows of them then of course in 1947 the Leak TL12.1...

 An e-mail landed this morning from a customer wanting to know what Jones plugs he would need for his R1155 and T1154.    I didn't ask whether or not his station had em all ripped out, however, here is a nice little aide memoir to anyone needing to remind themselves of pin configurations of these connectors for this particular use BUT don't forget that shown below are the CHASSIS configurations and that you need the corresponding connector ie plug to socket & socket to plug to match....

From this quaint photograph from 1928, you will see that valve damping to reduce microphonics is nothing new.   In this example, a pioneering radio enthusiast decided to apply his damping using Plasticine.  As we all know from our childhood, Plasticine, is the proprietary name for a rubbery mixture formed when  calcium stearate, petroleum jelly, palmitic and stearic acids and a dash of colour  and mixed together with the application of heat.  It has all sorts of uses from making Wallace's "wrong trousers" and many childhood models, some rude(!) as well as it seems of damping microphonics and protecting the glass...

Those clever chaps at GEC-Osram made some of the most memorable and sought after valves made by any manufacturer, they chose valve base styles that were not used by anyone else at the time and envelope shapes which were not at the time used by anyone else so why should their valve numbering system be the same as anyone elses?     Anyhow, I digress for here is a handy little table that will allow you to classify the kinky GEC from the vari-mu GEC - I hope you will find it useful: - Letter Identifier Classification A Industrial device...

My erstwhile inquisitor was referring of course to the type numbers, screen printed with printers ink on a valve envelope - what do they mean?    Well, let's start with what is commonly termed 'The Mullard System' and here is a nice little table to help you to decipher what the alphanumeric type codes mean, enjoy:-  I can hear some of you exclaiming 'Oho, but what about the second number ala ECC83?'   Well, the second number is what is known as the development type number, in the case of the ECC83, it was the third 6.3V heater, twin triode,...