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JoeAlders 26th April 2012 03:26 PM

Symbol for tube diode in LTspice
When trying to simulate a simple rectifier using the tube 5y3gt, I stumbled across
the problem that in LTspice there is no symbol available for the diode.
I see a triode and a pentode symbol available in the lib but cannot find this for a diode.
Am I looking in the wrong place?
Can someone help me please?

dchisholm 26th April 2012 04:40 PM

Open the "Triode" symbol in the LTSpice Symbol Editor ("File" > "Open" , with "Files of Type" set to "Symbols (*.asy)", then find the ". . . \Lib\Sym\Misc" directory in your LTSpice installation directory).

Use the graphical "Edit" > "Delete" tool ("scissors" icon) to remove the dashed lines representing the grid, and its associated symbol pin. Save the symbol with a new name. (In a location where you can find it again. Perhaps in a directory that is different from the default LTSpice symbol directory. Or maybe not. Library management is NOT a strong point in LTSpice.)

(More info in the LTSpice "Help" > "Help Topics" file, under "Schematic Capture" > "Creating New Symbols".)

Or, in the Yahoo "LTSpice USer's Group" at < >, go to "Files" > "Lib" > "Tubes_Valves" > "6AL5 Diode Tube" > "Tube_Diode.asy".

Then give some serious thought to how you want to organize your collection of symbols and simulation models . . .

And you will probably want to review the numerous discussion threads in the group where people ask how to add symbols and models to LTSpice.


JoeAlders 26th April 2012 06:29 PM

Hello Dave,

Thank you very much for your help!
I certainly will visit that yahoo group ( I am a reg. member).
I very much appreciate your help 'where to go' when visiting
that group. Saves a lot of time!
And yes, I already faced the problem of how to organize things...


JoeAlders 28th April 2012 03:54 PM

1 Attachment(s)
Continuing story
When trying to get this simple rectifier circuit running, I am stumbling across a very frustrating problem:
LTspice is complaining about floating nodes.
Both diodes have floating anode and cathode nodes in this circuit. Whatever I do like
anodes and cathodes grounding via high ohmig resistances, nothing helps.
What am I doing wrong?

sawreyrw 28th April 2012 04:15 PM

The file you posted doesn't include the diode symbol, but are you sure it only has 2 nodes? Is there a third one still present in the symbol?

JoeAlders 28th April 2012 06:32 PM

1 Attachment(s)

Originally Posted by sawreyrw (
The file you posted doesn't include the diode symbol, but are you sure it only has 2 nodes? Is there a third one still present in the symbol?

Sorry sawreyrw here it is. In the circuitdiagram only.
They do not allow to upload the asy file....

dchisholm 29th April 2012 02:29 AM

4 Attachment(s)
Diode symbol file is atch. Change name from "TubeDiode.txt" to "TubeDiode.asy". (Downloading the file and changing the name probably takes more effort than simply creating a new symbol from the "triode" symbol, as explained in my first response.)

JoeAlders' file "DiodeCircuit.asc" has an extra instance of the TubeDiode symbol. See atch image. I don't know the details of his "DI_5Y3GT.txt" model so I grabbed one of the models on the 'net, placed it directly on the schematic, and changed the model name. With those changes, the file simulates. See atch screenshot and *.asc files.


JoeAlders 29th April 2012 02:49 PM

Hello Dale,

Thank you very much for your valuable assistance in this matter!
I started to take the symbol of the triode and modified it into a diode (as you suggested earlier).
Then, saving it in C:\ Program Files\LTC\LTspiceIV\lib\sym\Misc\ or in the file where I put the schematic,
both ways resulted in that ‘floating nodes’ message.
Anyway, your ‘return’ schematic runs without any problems so I will use that for further analyses.
Your way of placing the model directly into the diagram I will adopt also.
Did not see this in any of the user manuals I browsed.


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