Hi Pat, Welcome to EasyEDA. Well done; your schematic was very close to being simulation ready! There were a couple of mistakes in it that are arguably more down to us not making a few simple things clear in the documentation than perhaps your inexperience with the tool. :) I have slightly modified your schematic and it now runs without errors: https://easyeda.com/file_view_LM317-and-Dual-TIP36C-fixed_y82kCUO6o.htm Below is an explanation of what I have changed and why. The simulation first failed with the following error: `Error(parse.c--checkvalid): reg: no such vector.` because the netlables had been written using a `-` (dash) character. In EasyEDA, netlabels, volprobe names, device and subckt names cannot contain `-` (dash) or ` ` (space) characters. Long names can be concatenated using the `_` (underscore) character. Once this was corrected, a second error was found: `Error(parse.c--checkvalid): base2: no such vector.` This was because two volprobes (Base1 and Base2) had been placed on the same net. Please also note that attaching a volprobe with a name that is different from that of a netlabel that is already attached to that net, will overwrite the netlabel. Please see: https://easyeda.com/Doc/Simulation-eBook/Introduction-to-using-a-simulator.htm#Probingvoltages There was also an error: `Error: unknown subckt: xu1 reg_in adj-pin reg_out lm317btg` because there is no spice model for the LM317BTG device. There is however, a generic LM317EE spice model. If required this model can be copied from the netlist and pasted (changing the symbol and the subckt name (check start and end of the subckt!) from LM317EE to LM317BTG to avoid confusion with the library model) into the schematic and then have some parametetsr edited - such as current limit - to more closely model a specific variant of the LM317 family of devices.

Andy, Thanks for the help and fixing the problems. I was aware of the volProbe naming and its affect on the net labeling. Also - to let you know - I created a new element/symbol for LM317BTG. I then downloaded from ON Semi the .subckt Spice3 text file and uploaded that into the subckt part of the symbol. I wanted to verify that part of the circuit worked and I had this correct before adding the bypass transistors. So I ran the voltage regulator shematic without the dual bypass transistors and everything worked fine. It was only after I added the bypass transistors that it didn't work. Your fixes discussed above are all good and will fix those issues. But I don't understand why you are getting the error - [Error: unknown subckt: xu1 reg_in adj-pin reg_out lm317btg]??

Andy, I made the fixes you suggested and ran the sim. It works and I don't have an issue with or get the error associated with the LM317BTG for reasons explained above. Can I assume that the reason you got that error was because you didn't have the subskt data avaible from the symbol I created?

Pat, Thanks in turn for explaining about the LM317BTG model. You're right. Because the OnSemi model is not in the library (for reasons of copyright etc.) and I haven't pasted into the schematic, I got the missing subckt error. If you have pasted it into your schematic then you won't see the error. Beware though the OnSemi licensing for their models and also the possibility that it won't behave the same as a real device if you do silly things to it. To try to avoid confusing newcomers to simulation, the EasyEDA (EE suffix) models are mostly crafted so that they do behave much the same as real devices if you do silly things to them. :)

@andyfierman hi Andy Easy EDA is showing this error tran simulation(s) aborted Error(parse.c--checkvalid): volprobe1: no such vector. ngspice-26 done you can check my schematic here is the link https://easyeda.com/editor#id=888ecfd30d0f48d1b03cc4f696e4cd15|11a9ce2491eb4a84b547354bb8deed87 please help

Hi Looli, Welcome to EasyEDA. There are a couple of reasons your schematic does not simulate. 1. There is no spice model available for the MP20045DN; 2. You have no power supply source defined in the schematic. To understand how to build and run simulations in EasyEDA please read - and play with all the simulations in - the EasyEDA Simulation eBook: https://docs.google.com/document/u/1/d/1OWZVVFRAe_2NW3WratpkA_SGuHa5AcRow5ZRfvcoVTU/pub Also: https://easyeda.com/forum/topic/How_to_find_simulatable_parts_in_EasyEDA-1YgasK2kC https://easyeda.com/forum/topic/The_best_way_to_design_a_PCB_in_EasyEDA-ThR3pwqIC https://easyeda.com/forum/topic/Net_naming_conventions-uOHBvN5nh and also look through the other posts in the Tips and Skill section of the forum. :)