Re: Blown Gecko 340

andyolney wrote:

>I have damaged one of my G340( terminals 2-3 show 1 ohm resistance)
>and I don't know why. This is the 2nd one and after Mariss was kind
>enough to repair the first, I redid the wiring completely per the
>schematic Tim Goldstein posted.
>
>What is puzzling me is the fact that I had 2 G340s working fine,

was

>jogging fine, set the speed and acceleration using Mach2, ran some
>test gcode rectangles, and had a couple of hours of run time. Yea!
>
>Yesterday went to make a first part, ran the program, moves fine,
>wrong zero, stop, try to jog to part zero and the g340 won't come

out

>of reset. Check resistance of mosfets and trm 2-3 is 1 ohm.
>
>I am looking for reasons for the failure. So far:
>
>Wiring error?
>Wiring is the same as the working axis and I did not touch alter it
>to my knowlege.
>
>

Highly improbable. One possibility is bad connections to the motor.
If the connections were failing during movement, it might cause a
transistor
to pop in the Gecko.

~~~~ I will check the crimp on connectors on the motor wires.

>Bad Motor?
>I have seen a discussion of bad/shorted windings on steppers

causing

>damage, could this apply?
>
>

Yes, it is possible, too. You can check the motor by applying a very
low
voltage, such as a single D cell, and looking for a jerk in the
rotation
or a
current spike as shown on a DVM in current mode.

Sometimes these motor defects can be intermittent, too. Is this
blown drive
attached to the same motor as when you last blew one? That might be
a strong clue that it is related to the motor, wiring, or something
particular
to that axis. What did you have the current limit set to?

~~~~ It was turned up pretty well. The inline 5A fuse did not blow
though.

What is your DC supply voltage? With high inductance motors, it is
possible
for current to flow back from the motor, through the drive, and
increase the
voltage on the DC supply. If the voltage goes high enough, the drive
will
pop.

~~~~ 36VDC. Should have plenty of head room here.

Do you have the recommended capacitors across the DC power input
terminals (or is that for the stepper drves only?)

~~~~Yes, 1000 microFarad

Jon

~~~~ Thanks for your suggestions. Andy