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Big Bad Bob Big Bad Bob is offline
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Default Triode Naming Convention

On 2020-08-29 01:50, Xtrchessreal wrote:
The question is simple: When it comes to schematics e.g. I see V1A and V1B How do I know which triode this refers to is V1A Pins 123 and V1B 678. Most data sheets indicate pins 123 to triode two and pins 678 to triode 1

In the Philips data sheet for a 12AX7 they even have a remark stating pins 678 or triode 1 is a better triode with regard to hum.

Some schematics actually show the pins for the specific triode but most only show V1A V2B V3B etc. Its obviously most critical in the first pre-amp stage unless there is a reason by the designer to have something a little different.

Can anyone explain this convention or lack there of?


yeah it's a little disturbing they're not being precise.

Only other thing I would do is look at the GE tube manual for how they
draw it, and maybe infer pin numbers and "which triode" from that.

which tube is it, 12AX7 or ?

The GE manual I'm looking at shows "section one" on pins 6,7,8 and
"section two" on pins 1,2,3. So I'm guessing 'V1A' would be section
one, and 'V1B' would be section two. If you look at the actual
equpment, maybe you can trace a pin to a component to verify?

assembly was often "by hand" back then with point-point wiring. The
schematic could be "the other way" and it still got built right. I
would expect they're all consistent within themselves, but when compared
to other gear... who knows?