19 Jul
2010
19 Jul
'10
8:11 p.m.
On 18 Jul 2010 at 19:44, Tony Duell wrote:
Only the 7xxxx is not the Loctal equivalent of the 6xxxx in genral. IIRC,
the 6Q7 became the 7C6, the 6V6 became the 7C5. No logic at all.
Is it just me, or are the common US valve numbers
pretty much
meaningless. The common UK/European ones, used by Philips/Mullard [1]
can be easily decoded to give the heater rating, electrode structure
and base type. US ones don't seem to give the electrode structure in
any meaningful way, even though that it probably the most important
thing [2].
It depends. 0xxx = cold-cathode, gas filled, 6xxxx = 6.3V heater,
12xxxx = 12.6v heater, of course. 7xxx, 14xxx, loctal versions. The last number is generally the number of elements in
earlier devices,
but that's a give-or-take. So 5Y3 and 5U4 are both directly-heated
And IIRC for octal valves, the metal envelope (early octals being those
RCA metal things, of course) counted as an element.
cathode full-wave rectifiers. 5 or 6 = beam power
tube or triode
with dual diode section. 7 = indirectly heated cathode pentode, or
combination oscillator-mixer (e.g. 6L7), also dual triode. 8 =
pentagrid converter (e.g. 6A8). But it's all approximate.
In other words, if oyu know what the valve is, fine, but there's no way
you'll work it out from the type number. But if somebody says to me
'EFM1', I know it's a combination signal pentode and 'magic eye'
indicator (yes, such a device did exist!) with a 6.3V heater on a P side
contact base. And a UCH81 is a triode-hexode freqeucny changer with a
100mA series-string heater on a B9A base. And so on
-tony