STJ7780
Cast Iron
- Joined
- Jul 9, 2009
- Location
- Dallas, Ga
Well I have looked all over and I have not come up with any solid info on repairing the servo drive boards for the older Haas brush style servo motors. I have 2 bad drive cards and it kills me to look at them and know that all of the components on the boards are easily replaced. If I could figure out what went bad, I could have a good working servo amp again for a fraction of a new or rebuilt card would cost me. So I thought I would start a thread on testing and repair of the Haas Servo AMP card. Try to gather collective information in an effort to find a fix for all of us. I am competent enough to test and solder on new components but the theory behind how the cards actually work is where I am in the dark.
So far on both my boards I have not burned or discolored areas. No burned smell or any other indication of irreparable damage. Both cards set servo overload alarms but the axis themselves were not overloaded and moved freely. Long story short, new card, axis works.
My gut reaction was to point the finger at the MOSFET transistors but they "look" OK and are difficult to test. The original style of mount transistor does not exist any more. But new ones do in the same electrical configuration so if they were bad, then new mounts and heat sinks would need to be made. Part# IXFH50N20-ND. Best I can tell, the controls command movement, the amp commands the servo on and looks for the encoder to show movement. When the encoder does not show movement, the alarm sets.
I have also come across a mention of the opto-isolator going out on these boards, but I am not sure how to test these.
Here are a few pictures of the boards I have.
Steve
So far on both my boards I have not burned or discolored areas. No burned smell or any other indication of irreparable damage. Both cards set servo overload alarms but the axis themselves were not overloaded and moved freely. Long story short, new card, axis works.
My gut reaction was to point the finger at the MOSFET transistors but they "look" OK and are difficult to test. The original style of mount transistor does not exist any more. But new ones do in the same electrical configuration so if they were bad, then new mounts and heat sinks would need to be made. Part# IXFH50N20-ND. Best I can tell, the controls command movement, the amp commands the servo on and looks for the encoder to show movement. When the encoder does not show movement, the alarm sets.
I have also come across a mention of the opto-isolator going out on these boards, but I am not sure how to test these.
Here are a few pictures of the boards I have.
Steve