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Blog posts of '2012' 'June'

NURSEY KNOWS BEST - SHOP WITH MULLARD MAGIC!

Now then, stand to attention as it is time for you to take your medicine!  The Mullard Magic nurse has just published an article in The Lancet citing irrefutable proof that buying items from the Mullard Magic website is good for MY health so please, do more buying - tee hee.    

Seriously though, we at Mullard Magic are proud to have supplied items to help a very keen group of 1940s re-enactors in their quest for originality not only in dress and accoutrements but also in the subject of their re-enactment - their wartime wedding re-enactment is not to be missed so why not find out more about Nurse R, who although a Red Cross Voluntary Aid Detatchment nurse is currently serving with the SOE on hush hush work.    Her husband, an RAF fighter pilot at Tangmere confided in me that she knows 17 ways to silently kill a man using only her bare hands and a bedpan.

Check out Nurse R, hubby and friends at  NAUGHTY NURSEY EXCITEMENT

EXOTIC COMPONENTRY IN THE MULLARD HIGH SPEED VALVE TESTER

At the time of introduction, two 'hollow state' devices the MHSVT contained were considered exotic.   The first, the 85A1 voltage regulator is a neon filled reference two electrode device which serves to provide the MHSVT with it's reference voltage stable in normal useage to 0.17% variance and over it's entire life. stable to within 0.5% of nominal value.     The second is the DG7/5 cathode ray tube which is an electrostatic medium persistance tube .    What is interesting is that this CRT is used in this application purely as a voltage indicator, measuring various currents by means of voltage drops across resistances brought into circuit by the punched card valve selectors.  No need for a timebase here you see.  

With the passage of 60 years or so, opinions change and now we consider a CRT and a neon regulator rather passe and instead become animated if not rather excited by the EL37 beam tetrode that a MHSVT also contains - more on this desirable audio valve in a future blog entry.

BUILDING THE MULLARD HIGH SPEED VALVE TESTER

These were selling like hot cakes in 1951 and details of their build and performance featured in much of the Mullard official literature of the time. Here we see Arnold Polkinhorne doing something with a Philips valve voltmeter.  Just look at that fat bottle EL37 lurking on the chassis as well as a stash of more MHSVT in the background.

 

The fun cotinues as here is Dorothy Prinkle nimbly constructing and lacing a wiring loom for a MHSVT - looks like she's using the silicon covered wire display from Phil Marrison's BVWS stall - haha!

THE MULLARD HIGH SPEED VALVE TESTER - AT THE DEALER NEAR YOU - NOW!

Resuming our Mullard story in 1951, we see that Mullard is still vigorously pushing the MHSVT and that it is being received with praise by the radio & TV trade.  Here we see Chris Evan's grandad posing with his machine, in his letter to Mullard he went on to explain how he is clawing back his purchase capital outlay by charging customers "a bob" to have their valves tested - he thought about doing it for free but thought that customers wouldn't appreciate a service they didn't pay for(!) -  that's the spirit!

 

And yes, the MHSVT really was at the dealer near you - NOW as this shop sign from sunny Norway shows.

NOT ITMA & TOMMY HANDLEY BUT RETMA AND THEIR VALVE NUMBERING SYSTEM!

Yo peeps, today we are going to look at the RETMA valve numbering system.   The Radio Electronics & Television Manufacturer's Association was formed in early 1953 and were pivotal in ensuring standardisation of American Valve numbering using the RETMA system.  Although primarily an American system, it was also used extensively in Europe with Mullard using it to label American valve types imported or manufactured at the old Edswan works.  In Britain, Brimar used the system extensively for most of their valve products.

A RETMA valve code always takes the following form: - 

NUMBER PREFIX/LETTER GROUP/NUMBER SUFFIX/ADDITIONAL LETTER(S) where: - 

 

The NUMBER PREFIX indicates the heater voltage, where: -

1 signifies a heater voltage within range 0.1 - 2.1V

2 signifies a heater voltage within range 2.1 - 2.9V 

3 signifies a heater voltage within range 3.0 - 3.9V

5 signifies a heater voltage within range 5.0 - 5.9V

6 signifies a heater voltage within range 6.0 - 6.9V

12 signifies a heater voltage within range 12.0 - 12.9V

Other voltages follow - you get the idea............

 

The LETTER GROUP indicates the valve type, where: - 

L as a first letter signifies a Loctal valve basing.

P as a second letter signifies a CRT.

S as either first or second letter signifies a single ended valve.

U, V, W, X, Y, Z all signify a rectifier type.

AB and other dual letters were sequentially assigned when single letters were all used.

 

The NUMBER SUFFIX indicates the number of sections and elements within an envelope or in the case of a CRT, the type of phosphor used.


The ADDITIONAL LETTER(S) provide additional type information, where: - 

A, B, C signify reverse compatible succesive versions.

E signifies an export device.

G signifies a glass envelope of ST-12 to ST-16 size.

GT signifies a glass envelope of T-9 size. 

GT/G signifies a glass envelope that will suit either G or GT applications.

L signifies a Loctal valve basing.

LM signifies a locking valve basing.

M signifies a metal envelope.

MG signifies a combination - metal-glass envelope.

ML signifies a combination metal-Loctal valve basing.

S signifies a spray shielded envelope.

W signifies a ruggedized valve for military or harsh environmental usage.

WA, WB signify a reverse compatible enhanced device.

X signifies a low loss ceramic base for HF - UHF applications.

Y signifies a low loss Micanol base for HF - UHF applications.

 

With this blog entry now complete, we have looked at all the major "modern" valve numbering systems and now you all know how to "read" a 12AX7 or an ECC83 or even a CV4004  it is now time to get back on track with more Mullard related entries.  

We will however revisit the topic of valve type numbering systems in the near future with a look at the more arcane numbering systems that were used from the dawn of radio right up until the mid 1930s.

 

WHAT CAN YOU TELL ME ABOUT THE MAZDA VALVE NUMBERING CODE?

Well, Mazda were another manufacturer who wanted to stand out and indeed made their own version of the Octal base with a fatter spigot known as the Mazda Octal or MO base.    Their valve numbering system was a bit kooky too and needs some explanation. 

The typical Mazda valve type number was an alphanumeric affair comprising of; a numerical prefix followed by a letter which in turn was followed by a mumerical suffix.

The numerical prefix always indicated the heater voltage EXCEPT where 10, 20 & 30 were used which indicated the heater current draw in 0.1A.  A further exception was for rectifier valves whose designation started only with a letter - eg U31, UU5 etc.

The letter indicated the valve type with letters allocated as per the following table.

C Frequeny changer
D Signal diode or diode(s)
F Signal tetrode/pentode
FD Signal tetrode/pentode plus diode(s)
FL Signal tetrode/pentode plus triode
K Thyratron
L Signal triode or triode(s)
LD Signal triode plus diode(s)
M Tuning indicator
P Output tetrode/pentode
PL Output tetrode/pentode plus triode
U Halfwave rectifier 
UU Fullwave rectifier 

The numerical suffix was a sequentially assigned development number.

Here are a couple of examples: -

UU5 -  the 5th full-wave rectifier developed by Mazda.

20P1 - the 1st 200mA  heater output pentode developed by Mazda.

 

I HAVE A BOX OF OSRAM VALVES - WHAT DO THE NUMBERS ON THEM MEAN?

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
B Twin triode
D Diode
GU Gas filled rectifier
GT Gas filled triode
H High imp.  triode
KT Kinkless tetrode
L Low imp. signal triode
MU Ind. heated rectifier
N Output pentode
P Output triode
QP Quiescent bi-triode
SU Tetrode
U Rectifier
VS Vari-mu tetrode
W Vari-mu pentode
X Frequency changer
Y Tuning indicator
Z Hi-slope pentode

The letter identifier or letter identifier sequence is followed by a sequentially allocated number which is the development number for a particular valve type eg;  KT66 = The 66th Kinkless Tetrode designed; KTW63 = the 63rd Kinkless Tetrode-Frequency changer (multi-electrode) valve designed.

IN 1926 CHILDREN LOVE GOOD RADIO BY MULLARD

 

Aah, this warm tone 'swallows 'n' amazons' scene provided courtesy of Mullard  from December 1936 is enough to warm the cockles of your heart.   These days the little darlings love iPods, iPhones and Facebook.   MInd you, as a not so little crotchety old git, I have to make allowances because I just love my new iMAC which should now help me put up more delectable thermionicalia up for perusal and purchase by my faithful customers.

AT MULLARD MAGIC, THEY NEVER BOUNCE!

 In 1951, Mullard were made aware of an absolutely hilarious occurence.    A proud owner had bought a Bush TV22 bakelite TV - you know the one, I think we have one on sale here.

Anyhow, he was moving it to try and find the best spot for it and guess what, in typical Mr Butterfingers Numpty style he dropped it and shattered the cae, however, all was not lost and the chassis and tube were quite fine and our slip fingered gent wrote to Mullard moaning about the fragility of Bush bakelite but praising the enduring qualities of Mullard glass.  

The TV22 bare chassis was retrofitted with an alternative casing and went on to provide sterling service safely ensconced in an orange box, tastefully painted in battleship grey, using a type of mica loaded paint designed for electricity pylon protection.

Could this be an early example of 'UPcycling' - goodness how I HATE that term!  Thus clothed, the set allowed a grateful family to watch the 1953 Coronation - huzzah, and very topical at this moment some  60 years on!

This episode prompted Mullard to publish the following cartoon in their in-house magazine featurung the eponymous Syd who espouses a salutory lesson to all of us who choose to monkey around with delicate thermionicalia  (is that a real scrabble-able word I wonder??). 

This wasn't the only accidental event extolling the longevity and hardiness of Mullard devices, so stick with watching this blog for other jolly japes of a similar kind - priceless@!

 

WHAT DO THOSE LETTERS AND NUMBERS ON A MULLARD VALVE MEAN?

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, B9A valve developed by Mullard.