Troubleshooting Triac Motor Control

Thread Starter


Joined Apr 27, 2009
I have a Xytronic 988 soldering station. It has served me well over the years and one day when I was swapping irons I accidentally attempted to plug in an iron into the wrong plug and I heard a pop and the station stopped working. Even thought the power was off there was AC at the handle plug and I shorted something. I pulled it apart and found a transistor blown apart. I figured it would be an easy fix.... One month, twenty plus dollars in parts and many changes of components it is still not working correctly.

The problem is on the right side, the handle with the solder vacuum pump. When you press the button on the handle the pump turns on and runs and when you let the button go, the pump will run for a few seconds, like it should and then there will be a big surge in current and sometimes it will blow the fuse on the Xytronic. This big surge shouldn't be there. Everything else is working as it should.

I looked into this circuit and it is using a zero crossing triac in a six pin DIP. A MOC 3041 this triggers the triac a BTA12 600C. What looks simple, and just might be has me perplexed. What would cause this big surge of current when the motor stops? Here is the schematic for that part.
Thank you