On Monday, March 5, 2012 12:10:59 PM UTC-8, wrote:
First of all, I don't expect I'll be able to get a definitive answer
because of the limited information I'll be able to give, but here
goes. I have a Fadal CNC mill that had in it a servo amp that was
failing. I replaced the amp with and would like to figure out what is
wrong with the original amp. 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. 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? 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. I think it's probably hopeless for someone
like me who knows little about electronics to find out what the actual
device is but I do like to figure things out and learn a little bit
more.
Thanks,
Eric

I agree with Frank. With limited experience, it mught be easier and cheaper to 'shotgun' replace all the electrolytics and resolder the whole board and see if that solves the problem.
I am assuming that you have checked to power supply section of the unit to see that the internal power voltages are stable. A simple drift of the 5V [?] rail during 'warm up' could easily be the culprit.

Neil S.