On Tue, 06 Mar 2012 08:44:12 +1100, Franc Zabkar
wrote:

On Mon, 05 Mar 2012 12:10:59 -0800, put finger to
keyboard and composed:

The amp is made by Advanced Motion
Controls. They do not offer schematics for the amp. None of the
devices on the circuit board can be identified by a part number
because Advanced Motion Controls ground the tops of all the devices to
remove any identifying information.

*******s!

The problem with the amp is that
it will not work until it's warm enough. So some device or devices
must be a minimum temperature before the amp will work. Once warm
enough it works perfectly. I thought I would try warming as small an
area as possible and move the heat source around to narrow down the
search area and then use cold spray to see if it is just one
component. What kind of devices need to be warm enough to work?

Electrolytic capacitors often dry out and produce thermal symptoms.
Otherwise you could have a dry solder joint.

And if I do narrow it down to just one device what are some of the things I
can test for? I cannot compare test points with a known good amp
because all the other amps in the machine are a different brand as is
the new one I just bought.

Servo problems are some of the most difficult to troubleshoot,
particularly when they involve motors. You need to open the control
loop and very carefully test each stage. When one component fails,
there can be catastrophic failures in other components.

Could you upload a photo of the PCB? Maybe someone will recognise it,
or at least be able to guess at the identities of the components from
the layout.

- Franc Zabkar
Greetings Frank,
I should have said that the CNC control decides when the servo amp is
working. What happens is that the control says there is a servo amp
error, not what the error is, until the amp is working properly. So
it's basically binary as far as the info the control gives me. Either
the amp is working or it's not. I don't know, and the troubleshooting
section of the CNC manual doesn't tell me, what the problem is or may
be. I just wait until the amp is warm enough and the control says it's
OK. Once warm enough it works perfectly and has been for a year at
least. I can post pictures, but where? This isn't a binary newsgroup.
I do post pictures for rcm on Metalworking.com.
Eric