Re: G201s repaired, now to bring up machine

Chris,

This is really important. Having the same set of MOSFETs blow up in
four seperate drives is a dead give away that there is a problem with
the motor. The odds against that happening randomly are 1:256.

Your motor may have a shorted turn. Shorted turns kill drives and
usually cannot be detected with an ohmmeter.

Mariss

--- In CAD_CAM_EDM_DRO@yahoogroups.com, Chris Brick <cbrick@t...>
wrote:

> Hello all,
>
> I've repaired two of my dead G201s, thanks to Mariss and others on

this

> list.
>
> It seems that the same pair of FETS blew on all 4 G201s. This is

the

> pair that the capacitor attaches to on the top of the board. Is

this

> phase weaker than others or is this a sign of problems somewhere

else.

> Three separate motors and two sets of motor wires have been

connected

> when failure has occurred. I'd doubt that all three of my motors

are

> damaged in the same exact manner, especially with the coils all

reading

> the same on the ohm meter.
>
> In order to avoid blowing things up again, I'm hoping to put some

things

> in place to help keep the current down while I focus on finding the
> problems.
>
> Last night I checked the motors with an ohm meter and all the

windings

> read 1.2Ohms. When I turn the motor they change and then come back

to

> 1.2 and hold. I checked the cables and connectors for

shorts/breaks and

> all are fine. I'd like to limit current between the motors and

Geckos.

> Back when I had a brain, I remember doing this with resistors. Is

this

> still the preferred method?
>
> I've got a 24V @16A switching PS with a 3700uF 450V cap I've been

using

> for bench testing. I'm wondering if I should use this power supply

for

> initial testing once I get the machine back together? Is the

3700uF cap

> going to give me enough leeway for the current to catch up when I

start

> moving motors? I've been using the 57.6vdc transformer/bridge/cap

combo

> for all testing and part smoking sessions in the past few weeks.

I'm

> hoping the 24V will help minimize any more damage if things are

still

> not working correctly.
>
> Thanks again for all the help. I'm continually amazed at the level

of

> knowledge and patience exhibited on this list.
>
> Cheers,
>
> Chris