LTspice QNANA

"....my understanding is that NAN stands for Not A Number."


I understand that as well---so it cannot compute that particular circuit. But, as I said, if I change a value by even a small amount, and then run it again, sometimes (not always) it works fine---which makes no sense---there is no 'divide by zero' or other causes and nothing obvious to me that triggers this error.
Do you have a link to that users' group?
 
"....my understanding is that NAN stands for Not A Number."


I understand that as well---so it cannot compute that particular circuit. But, as I said, if I change a value by even a small amount, and then run it again, sometimes (not always) it works fine---which makes no sense---there is no 'divide by zero' or other causes and nothing obvious to me that triggers this error.
Do you have a link to that users' group?

The link for the actual discussion of this error is
LTspice@groups.io | Issue with .#QNANV

Here's another one that mentions QNAN errors:
LTspice@groups.io | How to fine run simulation in LTspice with SiC SCT3022KL model ?

If you click on Messages on the home page and do a search for QNAN, a whole load of threads are listed that relate to this error.

dotneck335 said:
I tried that group, and even signed up for it. But it doesn't seem to DO anything---clicking on any of the links on that page just loops you back to the same page over and over again. Is there a trick?"

I really can't imagine why you are having problems. Have you made it work now?
 
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In fact I do see that error, but rarely - it's more common when I simulate tube circuits. I usually look for errors I have made, and sometimes I just need to slightly adjust a value to fix it. I have no actual idea what causes it, but I am assuming it is a math related error. Sometimes changing the solver or selecting a less rigorous set of solver parameters solves the problem.

I haven't seen the error lately though.

It's oddest when you have an actual circuit on the bench that works well and LTSpice tells you it doesn't work at all.
 
That's the CRAZY thing about the #Q NANA error---sometimes, if I change a resistor by as little as 1 ohm, the sim runs perfectly. In a range of values, some work and others don't---there doesn't seem to be any pattern to it that I can discern. It is some sort of math error; I just wish I could figure a way to minimize the NANA occurrence.