Looking for circuit drawing software

It depends on your needs. But many electronics-oriented programs are available for the Ubuntu:

• Oregano (has oregano package in universe repository) - it has tube

  

• XCircuit (has xcircuit package in universe repository)

  

• KiCAD EDA (has kicad package in universe repository)

  

• gEDA gschem (has geda-gschem package in universe repository)

  

• QUCS (may be installed from some PPAs - for example ppa:dac922/ppa)

  

• QUCS-S - QUCS with SPICE (has deb-packages on OpenSuSe build service)

  

Also you can try to find software in the Synaptic Package Manager application (in the Electronics sections).

After some additional digging around on the web, I found a number of downloadable symbol sheets and drawing instructions for -- I'm not kidding -- Libre Draw.

I haven't used Libre Draw in several years (it seemed only useful for making flow charts, and I didn't have a use for that). I downloaded one of the symbol sheets, and found that Libre Draw now has most of the tools I used to take for granted in NewDraw (the drawing module in NewDeal Office) -- and it's much easier to use than Inkscape.

Though I haven't found any pre-existing vacuum tube symbols, I can create my own (reusable) part symbols by drawing and grouping the individual objects into a composite that handles as a single "part". One potential limitation is "glue points" -- the "connector" (a self-routing line that stays attached to the objects at its ends) can only run from one "glue point" to another, and it appears Libre Draw only assigns four "glue points" to a grouped object, but I think I can get around this.

With available objects for inductors, capacitors, diodes, and so forth, I won't have to create every device symbol from scratch, and those I do, I can save to a worksheet and reuse. It appears, until I need circuit simulation and am willing to tackle that learning curve, that Libre Draw will do the job for me.

Here's an early example -- diodes, triodes, tetrodes, and pentodes, with both directly and indirectly heated cathodes.