Hello guys , sorry for my dumb question ... [https://easyeda\.com/editor\#id=\|81849bda2c7343c3901c17d790f5a619](https://easyeda.com/editor#id=%7C81849bda2c7343c3901c17d790f5a619) Why my simulation doesn't work? > Circuit: gooduntitled > > Doing analysis at TEMP = 27.000000 and TNOM = 27.000000 > Warning: singular matrix:  check nodes r1\_2 and r1\_2 > Note: Starting dynamic gmin stepping > Note: One successful gmin step > Note: One successful gmin step > Note: One successful gmin step > Note: One successful gmin step > Note: One successful gmin step > Note: One successful gmin step > Note: One successful gmin step > Note: One successful gmin step > Note: One successful gmin step > Note: One successful gmin step > Note: One successful gmin step > Warning: singular matrix:  check nodes r1\_2 and r1\_2 > > Warning: Dynamic gmin stepping failed > Note: Starting source stepping > Warning: singular matrix:  check nodes r1\_2 and r1\_2 > > Note: One successful gmin step > Note: One successful gmin step > Note: One successful gmin step > Note: One successful gmin step > Note: One successful gmin step > Note: One successful gmin step > Note: One successful gmin step > Note: One successful gmin step > Note: One successful gmin step > Note: One successful gmin step > Note: One successful gmin step > Note: One successful source step > Warning: singular matrix:  check nodes r1\_2 and r1\_2 > > Warning: singular matrix:  check nodes r1\_2 and r1\_2 > > Warning: source stepping failed > > Transient solution failed - > > Last Node Voltages > \-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\-\- > > Node                                   Last Voltage        Previous Iter > \-\-\-\-                                   \-\-\-\-\-\-\-\-\-\-\-\-        \-\-\-\-\-\-\-\-\-\-\-\-\- > r1_2                                              0                    0 > volprobe                                          0                    0 > v1#branch                                         0                    0 doAnalyses: iteration limit reached > tran simulation(s) aborted > Error(parse.c--checkvalid): volprobe: no such vector. > ngspice-26 done I need only to check a voltage with the probe. I'm trying to read the voltage probe documentation but without success. Thanks