Im looking for a chart that helps you translates the old tube symbol into the updated format. enter image description hereblank

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    \$\begingroup\$ Can you show an example of what you're talking about? \$\endgroup\$ – Dave Tweed Dec 5 '19 at 18:47
  • \$\begingroup\$ I'm not sure what you're asking, and from what I can tell it's probably off-topic. \$\endgroup\$ – Hearth Dec 5 '19 at 18:47
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    \$\begingroup\$ Based on this example, I guess white out the circle part? \$\endgroup\$ – Cristobol Polychronopolis Dec 5 '19 at 20:24
  • \$\begingroup\$ What "standard" is the new format? It seems to me that the old one is better as the circle indicates that all the elements are inside the glass tube. \$\endgroup\$ – Transistor Dec 5 '19 at 20:31
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    \$\begingroup\$ Both of those look like older formats. One thing about schematic symbols that you just have to get used to is that you just have to reconcile yourself to the fact that it's a human language, not an exact specification. So I'm going to use whatever I want when I draw schematics. In my case, that means I'm going to try to be up to date and standard, because I want to communicate effectively -- but the next guy over from me may want to make his schematic "pretty", or have some other agenda. You've just got to go with the flow. \$\endgroup\$ – TimWescott Dec 5 '19 at 21:55

Your tube symbol is indeed ancient. It seems to be a triode having three elements:

  • A directly-heated filament/cathode (filament + cathode are combined into one element)
  • A grid
  • A plate

ancient-to-modern tube symbols
Most modern tubes have indirectly-heated cathodes. They separate cathode and filament into two separate elements. If you do have a tube with directly-heated cathode, you would show this as a filament, and omit the cathode. You should make it clear that the filament symbol serves two purposes: cathode + filament.

Many modern tubes contain two triodes. Like 12AX7. They are shown with a split-open envelope. One would be titled 12AX7a, the other 12AX7b.

Tube base pin #'s are very often added to a schematic.
It is often customary to not show indirectly-heated filaments. Their wiring clutters-up a schematic diagram. Filaments are shown elsewhere on a schematic, with pin #'s and text added to show which tubes they belong to.

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    \$\begingroup\$ I love how "most modern tubes" really means 1928 onwards – that's literally more than 90 years of "modern indirectly heated cathodes". \$\endgroup\$ – Marcus Müller Dec 5 '19 at 21:30
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    \$\begingroup\$ @MarcusMüller Most modern tubes, on a per-unit basis, are magnetrons in home microwaves -- and unless I'm horribly mistaken, those use directly heated cathodes. Now, if you just look inside of guitar amps, and not inside of kitchens, then the story is different. \$\endgroup\$ – TimWescott Dec 5 '19 at 21:40
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    \$\begingroup\$ @TimWescott I agree – but point is that Glen really meant the low-power amplifier glass bulb tube kind, not the cool kind of tube. \$\endgroup\$ – Marcus Müller Dec 5 '19 at 21:44
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    \$\begingroup\$ @MarcusMüller Busted! Cathode;grid;plate seems most appropriate to tubes smaller than about 50kW. Haven't seen any microwave magnetrons with a grid. The OP's symbol seems too ancient for a klystron or TWT. Biggest I've worked around was a 3MeV accelerator, and an e-beam evaporator. \$\endgroup\$ – glen_geek Dec 5 '19 at 22:31
  • \$\begingroup\$ @glen_geek niiiiice :) \$\endgroup\$ – Marcus Müller Dec 5 '19 at 22:33

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