19 Jul
2010
19 Jul
'10
10:25 p.m.
It's like navigating around Boston--if you
lived there, you'd know
where you were headed.
Most of the US tube numbering systems are today fairly meaningless,
and yes, the best way to know what tubes you are looking at is to
pretty much know what circuits you are looking at. The initial "standard" (an example would be UV-201) set
by RCA was quickly
corrupted by the independents, so the industry set up a new standard
that we all (US) know and love. I suspect that the choice to
standardize the filament voltage and active number of elements in the
type number, yet leave out the basic function, was driven by the idea
that many radio designs could easily morph, simply with a tube swap,
in order to meet a new demand. An example might be changing a standard
AC power radio into a farm set into a car radio - mostly with only a
tube swap involving filament changes. In an early 1930s context, this
Except that most of the time when there are 2 valves differing only in
filament voltage, it's not just the first digits that change. The 50L6 is
a lot closer to a 6V6 than to a 6L6 from what I remember. And I mentioned
in my other post about the random changes beteween octal and loctal numbers.
In a sense the Mullard/Philips code had similar problems, but at least
you could be sure that both an EL84 and a UL84 were output pentodes on a
B9A base. And many cases, valves differing only in the first letter were
identical apart from the heater rating (e.g. EL81 and PL81).
The European system used this same idea, tried to
encode a little more
into the type numbers, but still managed to corrupt itself. An article
in Tube Collector magazine outlined the system, and there are an
astonishing amount of inconsistencies. In a way, it tried to be too
There are some inconsistencies early on (valves with the digits giving a
number <20 but having an octal base being the main ones that I've seen),
but an awful lot of the so-called inconsistences are from people who
don't realise that the code changed somewhat when the final number went
from 2 to 3 digits. In particular the initial letter
'G' was originally
for 5V heaters (e.g. GZ34 rectifier), later it was used
for miscelaneuous
heater ratings 9e.g. the GY501 EHT rectifier which has a 3.15V filament
IIRC), and that 2x (2 digits) means a loctal base while 2xx means a B10B
paaase, and 5x means a B9G base while 5xx means a B9D base.
clever.
Of all these systems, the most simple ones tend to be the best - do
not encode anything into the type numbers. If a tube user needs to
figure out just what a specific tube type does, he probably has no
business sticking his nose into the radio in the first place.
Eh? If you can honestly work out what valves do without looking at their
numbers (which is what you imply), you are clevere than any engineer I
hve ever met. Most of us look up the numbers in a databook if we're not sure.
The award for most retarded tube numbering must go to the British.
Apart from the military's CV (common valve) system, which almost
nobody but the military uses, the British system was a mess, with
numbers and formats specific to the government agency or industry that
wrote the databooks. Often these numbers would even foul each other.
The best example is the VT90. If you ordered a VT90 each from the
Army, Air Ministry, and Post Office, you would get three completely
incompatible tubes. And during World War 2, if you ordered a VT90 in
I know the Air FOrce one (IIRC it's 'Valve, Transmitting', while VCR was
'Valve, Cathode Ray' (i.e a CRT, such as the famous VCR97 radar CRT that
was used for the first Williams stores after the war). I've not come
across it for Army valves, I thoght those normally started with 'A' (for
'Army' :-)). such as 'ARP12' (Army Receiving Pentode).
Britain, you might get a humble little US made 6H6
dual diode - a
"fourth" VT90.
DO you mean 'Britain' here? I assume you're refering to the US military
code where it stood for 'Vacuum Tube' (even if the device was gas-filled :-))
While it clearly helps having a consistent coding system if you are
trying to win a war, I see no reason to expect that different
manufacturers or agencies would necessarily have the same coding scheme.
Would you expect an Intel 4040 and an RCA 4040 to be the same chip?
-tony