Jshwaa
07-15-2007, 05:03 AM
This one is simple enough. Probably easier then a FET stack on an xmod. Here's what you need, but of course....some clippers, solder, copper braid, etc., will be helpful.
First rip your old FET's off like a wild animal, like you hate your old FET's for they are stinky and weak.
http://i83.photobucket.com/albums/j314/Jshwaa/IMG_2450.jpg
With some soldering iron, copper braid, and skills, carefull work the remaining peices of the old FET's and old solder out of the holes. Careful not to mess up the traces and copper cladding around the holes. If you remove too much, then it will be hard to solder the new ones on and be sure that the solder is reaching both sides of the circuit board, because the FET's are seated ALL the way down where the bottom of the epoxy casing touches PCB. No room to get a soldering iron underneath and be sure that solder bleeds all the way over to the other side and makes a firm connection.
Once you get the solder worked out and rework the copper holes back in place, work the legs of the FET's through the board until FET meets board.
Solder liberally and trim.
Put it all back together, place heat sink....
Now we test.....my favorite part.
The ideal test would be to load the FET's and monitor current draw and heat, while maintaining a voltage. So we'll hook a dummy load(1 ohm power resistor) to the motor leads and connect my power supply to the power leads, fire up the remote and see if you have control of power without smoke billowing or a FET getting extremely hot.
http://i83.photobucket.com/albums/j314/Jshwaa/IMG_2459.jpg
http://i83.photobucket.com/albums/j314/Jshwaa/IMG_2458.jpg
I get some decent current draw through the load resistor, which heats it up to a blistering heat in no time, but the FET's stay at room temp. And that's without the heat sink. Notice the voltage applied(7.22V), the current drawn by the board AND the load(6.41A), and the voltage at the load resistor(6.627V). And then as a double check that we are all good, I connected the steering servo and checked functionality. Success.
*BTW* I would have included more pics on the subject, but this forum is kind of funny like that.....
First rip your old FET's off like a wild animal, like you hate your old FET's for they are stinky and weak.
http://i83.photobucket.com/albums/j314/Jshwaa/IMG_2450.jpg
With some soldering iron, copper braid, and skills, carefull work the remaining peices of the old FET's and old solder out of the holes. Careful not to mess up the traces and copper cladding around the holes. If you remove too much, then it will be hard to solder the new ones on and be sure that the solder is reaching both sides of the circuit board, because the FET's are seated ALL the way down where the bottom of the epoxy casing touches PCB. No room to get a soldering iron underneath and be sure that solder bleeds all the way over to the other side and makes a firm connection.
Once you get the solder worked out and rework the copper holes back in place, work the legs of the FET's through the board until FET meets board.
Solder liberally and trim.
Put it all back together, place heat sink....
Now we test.....my favorite part.
The ideal test would be to load the FET's and monitor current draw and heat, while maintaining a voltage. So we'll hook a dummy load(1 ohm power resistor) to the motor leads and connect my power supply to the power leads, fire up the remote and see if you have control of power without smoke billowing or a FET getting extremely hot.
http://i83.photobucket.com/albums/j314/Jshwaa/IMG_2459.jpg
http://i83.photobucket.com/albums/j314/Jshwaa/IMG_2458.jpg
I get some decent current draw through the load resistor, which heats it up to a blistering heat in no time, but the FET's stay at room temp. And that's without the heat sink. Notice the voltage applied(7.22V), the current drawn by the board AND the load(6.41A), and the voltage at the load resistor(6.627V). And then as a double check that we are all good, I connected the steering servo and checked functionality. Success.
*BTW* I would have included more pics on the subject, but this forum is kind of funny like that.....