Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems.

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Default Servo amp repair

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
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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
--
Please remove one 'i' from my address when replying by email.
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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
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Default Servo amp repair

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.


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Default Servo amp repair



"nesesu" wrote in message
news:831[email protected]...
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.




I would second the resoldering of all solder joints.
It might well take you less time than it would take to post a reply to this
newsgroup, and even if it does not cure the problem, you can then be sure it
is not down to a dry joint.

Having reliable information on what is definitely NOT the problem can be
very valuable.



Gareth.

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Default Servo amp repair



"Jon Elson" wrote in message
...
wrote:

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.


Very likely there is a bad connection, either a solder joint on a
component or a connector. Look over all the solder joints and
see if you can find one that is cracked. You may need to use a jeweler's
loupe or other magnifier to find it. It would be best to find this by
inspection, but if you can't, you can try to find it by applying force to
the board while running. (Of course, watch out for the high voltages!)

Otherwise, if there are plug-in boards or modules, check the connectors
there for dirt or corrosion.

It obviously is not a totally failed component or it wouldn't work
at all. While it is possible there is a temperature-sensitive component,
that kind of thing is fairly rare, and usually they fail when hot, not
cold.

Jon



That, however, is not the case for electrolytics. They fail more regularly
than any other component in modern electronics, and a failure to operate
correctly when cold is a very common thing with them. If that was the
problem with the OP's board, an ESR meter would almost certainly find the
offender in very short order on a cold board.

Otherwise, I concur with everyone else that a bad joint is the next most
likely failure area, followed by any semiconductor on the board. It is
normally fairly easy to find such problems with the help of a hairdryer, a
can of freezer spray, and a little bit of cardboard to confine where the
freezer gets to.

As to the tops being ground off the semis, this used to be very common a few
years ago. It often indicates that the devices used are actually very cheap
and common types, and that they just don't want you to know this, ensuring
that defective boards are returned to them for repair. An experienced
service person can often work backwards to determine what a device is, by
reverse engineering the area of board that the IC or whatever is located in,
and checking waveforms and voltages on its pins.

Arfa

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On Wed, 7 Mar 2012 15:26:07 -0000, "Arfa Daily"
wrote:



"Jon Elson" wrote in message
m...
wrote:

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.


Very likely there is a bad connection, either a solder joint on a
component or a connector. Look over all the solder joints and
see if you can find one that is cracked. You may need to use a jeweler's
loupe or other magnifier to find it. It would be best to find this by
inspection, but if you can't, you can try to find it by applying force to
the board while running. (Of course, watch out for the high voltages!)

Otherwise, if there are plug-in boards or modules, check the connectors
there for dirt or corrosion.

It obviously is not a totally failed component or it wouldn't work
at all. While it is possible there is a temperature-sensitive component,
that kind of thing is fairly rare, and usually they fail when hot, not
cold.

Jon



That, however, is not the case for electrolytics. They fail more regularly
than any other component in modern electronics, and a failure to operate
correctly when cold is a very common thing with them. If that was the
problem with the OP's board, an ESR meter would almost certainly find the
offender in very short order on a cold board.

Otherwise, I concur with everyone else that a bad joint is the next most
likely failure area, followed by any semiconductor on the board. It is
normally fairly easy to find such problems with the help of a hairdryer, a
can of freezer spray, and a little bit of cardboard to confine where the
freezer gets to.

As to the tops being ground off the semis, this used to be very common a few
years ago. It often indicates that the devices used are actually very cheap
and common types, and that they just don't want you to know this, ensuring
that defective boards are returned to them for repair. An experienced
service person can often work backwards to determine what a device is, by
reverse engineering the area of board that the IC or whatever is located in,
and checking waveforms and voltages on its pins.

Arfa

Thanks everyone for the replies so far. I will post a picture in the
metalworking.com dropbox later today. I think I'll try replacing any
electrolytics first and then try the solder joint thing. I did talk to
another Fadal owner who has these servo amps in his mills and they
exhibit the same behavior. He has been using these machines over 40
hours a week for at least a couple of years by using a hair dryer to
warm the boards in the morning. Once warmed this way the machines will
run fine all day.
Eric


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wrote in message
...
On Wed, 7 Mar 2012 15:26:07 -0000, "Arfa Daily"
wrote:



"Jon Elson" wrote in message
m...
wrote:

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.

Very likely there is a bad connection, either a solder joint on a
component or a connector. Look over all the solder joints and
see if you can find one that is cracked. You may need to use a

jeweler's
loupe or other magnifier to find it. It would be best to find this by
inspection, but if you can't, you can try to find it by applying force

to
the board while running. (Of course, watch out for the high voltages!)

Otherwise, if there are plug-in boards or modules, check the connectors
there for dirt or corrosion.

It obviously is not a totally failed component or it wouldn't work
at all. While it is possible there is a temperature-sensitive

component,
that kind of thing is fairly rare, and usually they fail when hot, not
cold.

Jon



That, however, is not the case for electrolytics. They fail more

regularly
than any other component in modern electronics, and a failure to operate
correctly when cold is a very common thing with them. If that was the
problem with the OP's board, an ESR meter would almost certainly find the
offender in very short order on a cold board.

Otherwise, I concur with everyone else that a bad joint is the next most
likely failure area, followed by any semiconductor on the board. It is
normally fairly easy to find such problems with the help of a hairdryer,

a
can of freezer spray, and a little bit of cardboard to confine where the
freezer gets to.

As to the tops being ground off the semis, this used to be very common a

few
years ago. It often indicates that the devices used are actually very

cheap
and common types, and that they just don't want you to know this,

ensuring
that defective boards are returned to them for repair. An experienced
service person can often work backwards to determine what a device is, by
reverse engineering the area of board that the IC or whatever is located

in,
and checking waveforms and voltages on its pins.

Arfa

Thanks everyone for the replies so far. I will post a picture in the
metalworking.com dropbox later today. I think I'll try replacing any
electrolytics first and then try the solder joint thing. I did talk to
another Fadal owner who has these servo amps in his mills and they
exhibit the same behavior. He has been using these machines over 40
hours a week for at least a couple of years by using a hair dryer to
warm the boards in the morning. Once warmed this way the machines will
run fine all day.
Eric



If localised cooling/heating ellicits nothing, then ssuming it consists of
main series TTL/4000 desolder one IC at a time, place on an IC logic tester
in search mode that will then show what device type. If a generic fault ,
not even a batch fault, then unlikely to be a problem with the IC/straight
logic, more like an R or C or something drifting and upsetting timing of a
monostable or something.
Start with the ICs with most Rs and Cs around them


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N_Cook wrote:

If localised cooling/heating ellicits nothing, then ssuming it consists of
main series TTL/4000 desolder one IC at a time, place on an IC logic tester
in search mode that will then show what device type. If a generic fault ,
not even a batch fault, then unlikely to be a problem with the IC/straight
logic, more like an R or C or something drifting and upsetting timing of a
monostable or something.
Start with the ICs with most Rs and Cs around them



Has anyone ever used a place like this for support?

http://www.providenceindustrial.com/pricing_rush.php


--
You can't have a sense of humor, if you have no sense.
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Michael A. Terrell wrote in message
m...

N_Cook wrote:

If localised cooling/heating ellicits nothing, then ssuming it consists

of
main series TTL/4000 desolder one IC at a time, place on an IC logic

tester
in search mode that will then show what device type. If a generic fault

,
not even a batch fault, then unlikely to be a problem with the

IC/straight
logic, more like an R or C or something drifting and upsetting timing of

a
monostable or something.
Start with the ICs with most Rs and Cs around them



Has anyone ever used a place like this for support?

http://www.providenceindustrial.com/pricing_rush.php


--
You can't have a sense of humor, if you have no sense.



I've always assumed its like those "sourcing" companies with big bucks
upfront, flaff about a bit, and then come up with nothing


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Michael A. Terrell wrote:



Has anyone ever used a place like this for support?

http://www.providenceindustrial.com/pricing_rush.php


Don't know anything about them, but if they are one of the vultures
selling used gear, this might sell you more servo amps with the
same fault. Anything they have will likely be the same vintage as
your gear.

Jon


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Jon Elson wrote:

Michael A. Terrell wrote:


Has anyone ever used a place like this for support?

http://www.providenceindustrial.com/pricing_rush.php


Don't know anything about them, but if they are one of the vultures
selling used gear, this might sell you more servo amps with the
same fault. Anything they have will likely be the same vintage as
your gear.



??? All I saw was repair services.


--
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wrote in message
...
On Wed, 7 Mar 2012 15:26:07 -0000, "Arfa Daily"
wrote:



"Jon Elson" wrote in message
om...
wrote:

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.

Very likely there is a bad connection, either a solder joint on a
component or a connector. Look over all the solder joints and
see if you can find one that is cracked. You may need to use a
jeweler's
loupe or other magnifier to find it. It would be best to find this by
inspection, but if you can't, you can try to find it by applying force
to
the board while running. (Of course, watch out for the high voltages!)

Otherwise, if there are plug-in boards or modules, check the connectors
there for dirt or corrosion.

It obviously is not a totally failed component or it wouldn't work
at all. While it is possible there is a temperature-sensitive
component,
that kind of thing is fairly rare, and usually they fail when hot, not
cold.

Jon



That, however, is not the case for electrolytics. They fail more regularly
than any other component in modern electronics, and a failure to operate
correctly when cold is a very common thing with them. If that was the
problem with the OP's board, an ESR meter would almost certainly find the
offender in very short order on a cold board.

Otherwise, I concur with everyone else that a bad joint is the next most
likely failure area, followed by any semiconductor on the board. It is
normally fairly easy to find such problems with the help of a hairdryer, a
can of freezer spray, and a little bit of cardboard to confine where the
freezer gets to.

As to the tops being ground off the semis, this used to be very common a
few
years ago. It often indicates that the devices used are actually very
cheap
and common types, and that they just don't want you to know this, ensuring
that defective boards are returned to them for repair. An experienced
service person can often work backwards to determine what a device is, by
reverse engineering the area of board that the IC or whatever is located
in,
and checking waveforms and voltages on its pins.

Arfa

Thanks everyone for the replies so far. I will post a picture in the
metalworking.com dropbox later today. I think I'll try replacing any
electrolytics first and then try the solder joint thing. I did talk to
another Fadal owner who has these servo amps in his mills and they
exhibit the same behavior. He has been using these machines over 40
hours a week for at least a couple of years by using a hair dryer to
warm the boards in the morning. Once warmed this way the machines will
run fine all day.
Eric


As well as electrolytics, just have a look to see if there are any crystals,
resonators, or hybrid clock generators on the board. These are also all
components which can, and often do, exhibit a similar cold / warm failure
mode.

Arfa

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On Fri, 09 Mar 2012 17:09:24 -0600, Jon Elson
wrote:

wrote:

r. I will post a picture in the
metalworking.com dropbox later today. I think I'll try replacing any
electrolytics first and then try the solder joint thing. I did talk to
another Fadal owner who has these servo amps in his mills and they
exhibit the same behavior. He has been using these machines over 40
hours a week for at least a couple of years by using a hair dryer to
warm the boards in the morning. Once warmed this way the machines will
run fine all day.


Well, that's a RIOT! hair dryer? OK, with this additional info, it
is beginning to sound like a systematic problem, so the electrolytic
problem may be it. Hope you find it.

Jon

I took pictures today but forgot to bring the camera home so I will
post pictures tomorrow in the Metalworking dot com dropbox. There are
two or three electrolytics along one edge of the board and as these
are the only electrolytics (as far as I can tell) on the board I'll
replace them. I did look for any suspect solder joints with a 10x
loupe and didn't see any bad looking joints. Perhaps when the pictures
are posted someone will be able to give me an idea of what some of the
components may be.
Eric
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