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Posted by STEVE M on

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: - 
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.

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