RE: [CAD_CAM_EDM_DRO] Re: Here we go again - more trouble

And I will chime in, too.

Disconnect the motor from a known good drive, take the fuse out on that
drive, and see if you still get voltage across THAT fuse holder.

Most people don't realize that in a circuit, if you "open" the circuit, and
current stops flowing, you will measure the entire power supply voltage
across the "opening". This is easily seen by applying Kirchoff's law, when
you will see that with no current flowing(open circuit) there will be no
voltage drop across any of the things that usually drop voltage(by I*R), so
the entire Supply voltage must be "dropped" across the open circuit.

This is why switching the Neutral instead of the Hot in AC power wiring is
not a good idea, with the switch in the Neutral line, there will bo one
White wire on the switch that is at 120VAC(or whatever your color code/line
voltage is). Most people look at a white wire as "safe to touch", but in
this instance it would not be safe.

Andy Wander
Verrex Corporation


-----Original Message-----
From: washcomp [mailto:jeff@...]
Sent: Wednesday, October 20, 2004 9:47 AM
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: [CAD_CAM_EDM_DRO] Re: Here we go again - more trouble



Keith:

I picked up this part of the thread rather late so I appologize if
someone has suggested this before:

The problem with troubleshooting a complete system is that a problem
with one part often affects other components making the finding of
the bug difficult.

Try to break the system in half (thirds?). The problem is either
with the motor or the drive or the wiring harness. We'll assume for
now that your drive is good (it's new after all) - oh hell, lets test
it anyway. Tie the drive to a known working motor and see if all is
as expected. OK, now we know it's OK. Test the windings of the
motor for expected resistance as compared to your good motor
(assuming they are identicle). If the resistance you get is too
small to accurately measure, tie the coils in series and measure
across all of them. If this doesn't work (reading still too small),
take a battery and put the windings across it in series and measure
the voltage across each winding. They should be the same (ohm's law
and all that). If this all checks out then the motor should be OK.

If the motor is OK and the drive is OK, that leaves your wiring. I'm
not sure how you made up the harness, but likely there's some issue
(broken wire, shorted wire, mis-labled wire etc.).

Might want to check wiring to the fuse holder from the power supply
and the fuse/fuse holder while you're at it as long as everything is
disassembled anyway. It's consivable that the issue is there :-)

Hope this helps,
Jeff


--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Keith Clark" <mail@t...>
wrote:

>
> I thought that the voltage reading across the open fuse holder
> suggested a problem and did not know that that was normal. At any
> rate, I disconnected the motor and still found the same voltage
> reading across the open fuse holder. So at that point I reasoned
> that there must be something wrong with the connector from the

Gecko

> and replaced it. Then the reading across the fuse holder went to
> zero! However, this was done without the capacitor installed

across

> terminals 1 and 2. Does it seem possible that the connector could

be

> bad? I did not see any stray strands of wire and could not measure
> any shorts between the terminals of the connector. Possibly the
> capacitor in place makes a difference? I did replace the capacitor.
>
> Thanks
> Keith Clark

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