Sosijdog
New Member
- Messages
- 12
- Location
- Shetland Islands
I have roughly marked up the path from the suspect PNP transistor, through the load resistor into the brake SCR gate.
When this was disconnected (unsoldered gate side of resistor) everything worked perfectly. The only noticeable difference was the motor run LED on the board faded out as supposed to turning off immediately. This shows the power in the motor was decaying due to the absence of braking and back emf.
Once the resistor was reconnected it immediately blew the fuse as before. So this is definitely the cause.... the gate is being triggered somehow through this PNP transistor. I assumed it would be more likely that this transistor is the cause as it is the switching element. However following testing of the component and subsequent de-soldering/soldering back onto the board the problem rectified itself...
i now need to wait until the fault occurs again to be sure a transistor replacement will infact cure the issue.
the owner took the welder back and used it in anger for nearly 2 hours @ setting 5 with absolutely no problems.
So thanks to you guys here for taking the time to help out/suggest things to try. Without you i would still be stumped.
i will update again if the problem surfaces again.