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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Old March 18th 14, 05:29 PM posted to sci.electronics.repair
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Default A sign of dirty connectors?

Greetings All,
One of my CNC mills has a problem. The machine, a Fadal 15XT, built in
1998, (I think), keeps showing an alarm for a malfunction the machine
can't have. There is a machine interface board that, among other
things, monitors for lube oil and air pressure with a couple sensors.
My machine uses grease instead of lube oil and does not use air in the
spindle oil mist system because my machine also has a grease packed
spindle. So there are not even sensors for the board to monitor and
report to the operator. Anyway, after the machine has been running a
while so that the electronics cabinet is warm inside the alarms start.
If the cabinet is opened and the board in question is allowed to cool
the alarms would stop. But then even the tactic of running the machine
with the cabinet open would not prevent the board from throwing alarms
after being on a few hours. If I turn off the machine and let it cool
for even 4 hours the board will still throw alarms. However, if I
remove the board and put it back in the alarms stop. After running the
machine several days the whole thing starts over again and the only
remedy seems to be removing and re-inserting the board. I have cleaned
the contacts with alcohol and "contact cleaner". The contact cleaner
is some type of chlorinated hydrocarbon solvent, the same stuff is
also sold as brake cleaner from the same maker. So after the long
winded explanation above I am wondering if dirty contacts could
somehow make the board run warm and cause the alarms. If that's the
case I'll buy some Deoxit or similar and try it out. Otherwise I'm
looking at about $500.00 to get a repaired board on an exchange basis.
The only boards available for this machine are as old as mine.
Eric

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Old March 18th 14, 05:41 PM posted to sci.electronics.repair
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Default A sign of dirty connectors?

wrote:
Greetings All,
One of my CNC mills has a problem. The machine, a Fadal 15XT, built in
1998, (I think), keeps showing an alarm for a malfunction the machine
can't have. There is a machine interface board that, among other
things, monitors for lube oil and air pressure with a couple sensors.
My machine uses grease instead of lube oil and does not use air in the
spindle oil mist system because my machine also has a grease packed
spindle. So there are not even sensors for the board to monitor and
report to the operator. Anyway, after the machine has been running a
while so that the electronics cabinet is warm inside the alarms start.
If the cabinet is opened and the board in question is allowed to cool
the alarms would stop. But then even the tactic of running the machine
with the cabinet open would not prevent the board from throwing alarms
after being on a few hours. If I turn off the machine and let it cool
for even 4 hours the board will still throw alarms. However, if I
remove the board and put it back in the alarms stop. After running the
machine several days the whole thing starts over again and the only
remedy seems to be removing and re-inserting the board. I have cleaned
the contacts with alcohol and "contact cleaner". The contact cleaner
is some type of chlorinated hydrocarbon solvent, the same stuff is
also sold as brake cleaner from the same maker. So after the long
winded explanation above I am wondering if dirty contacts could
somehow make the board run warm and cause the alarms. If that's the
case I'll buy some Deoxit or similar and try it out. Otherwise I'm
looking at about $500.00 to get a repaired board on an exchange basis.
The only boards available for this machine are as old as mine.
Eric


I'm not sure of what contacts and connectors you're dealing with, but
consider the solder to them may be bad. The wear and tear on a flakey
connector (if that's the problem) only goes up when you fuss with it more.

Bad connectors can get hot, if they're handing enough current. I've seem
them go up in flames once the arcing starts. There's nothing like
scrubbing black soot off circuit boards after the fireworks show is over.

Not surprisingly discolored, or melted looking connectors are always a
warning sign.

Intermittent problems with heat still point to connection problems, even
if on the PCB itself, and not the connector.

I fixed one board recently in a timer board that was "intermittent" that
had only 7 broken and bad solder joints. How it worked at all was a
mystery.




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Old March 18th 14, 10:16 PM posted to sci.electronics.repair
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Default A sign of dirty connectors?

On Tue, 18 Mar 2014 16:41:42 +0000 (UTC), Cydrome Leader
wrote:

wrote:
Greetings All,
One of my CNC mills has a problem. The machine, a Fadal 15XT, built in
1998, (I think), keeps showing an alarm for a malfunction the machine
can't have. There is a machine interface board that, among other
things, monitors for lube oil and air pressure with a couple sensors.
My machine uses grease instead of lube oil and does not use air in the
spindle oil mist system because my machine also has a grease packed
spindle. So there are not even sensors for the board to monitor and
report to the operator. Anyway, after the machine has been running a
while so that the electronics cabinet is warm inside the alarms start.
If the cabinet is opened and the board in question is allowed to cool
the alarms would stop. But then even the tactic of running the machine
with the cabinet open would not prevent the board from throwing alarms
after being on a few hours. If I turn off the machine and let it cool
for even 4 hours the board will still throw alarms. However, if I
remove the board and put it back in the alarms stop. After running the
machine several days the whole thing starts over again and the only
remedy seems to be removing and re-inserting the board. I have cleaned
the contacts with alcohol and "contact cleaner". The contact cleaner
is some type of chlorinated hydrocarbon solvent, the same stuff is
also sold as brake cleaner from the same maker. So after the long
winded explanation above I am wondering if dirty contacts could
somehow make the board run warm and cause the alarms. If that's the
case I'll buy some Deoxit or similar and try it out. Otherwise I'm
looking at about $500.00 to get a repaired board on an exchange basis.
The only boards available for this machine are as old as mine.
Eric


I'm not sure of what contacts and connectors you're dealing with, but
consider the solder to them may be bad. The wear and tear on a flakey
connector (if that's the problem) only goes up when you fuss with it more.

Bad connectors can get hot, if they're handing enough current. I've seem
them go up in flames once the arcing starts. There's nothing like
scrubbing black soot off circuit boards after the fireworks show is over.

Not surprisingly discolored, or melted looking connectors are always a
warning sign.

Intermittent problems with heat still point to connection problems, even
if on the PCB itself, and not the connector.

I fixed one board recently in a timer board that was "intermittent" that
had only 7 broken and bad solder joints. How it worked at all was a
mystery.



The connector in question is an edge connector on the circuit board.
It plugs into another circuit board mounted connector. I will check
for solder joints that are bad, that's a good idea. I hope the bad
solder joints aren't on the board it plugs into. It's the board that
all the other boards plug into.
Eric

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Old March 19th 14, 02:34 AM posted to sci.electronics.repair
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Posts: 182
Default A sign of dirty connectors?

wrote:
One of my CNC mills has a problem. The machine, a Fadal 15XT, built in
1998, (I think), keeps showing an alarm for a malfunction the machine
can't have.


Does the problem board have any mechanical support other than the edge
connector? Is this support aligned correctly and connected? (Example:
the bracket on most PC expansion cards that screws down to the chassis.)

You might also look for metal debris, oil, old grease, dried coolant,
etc, on both sides of the problem board and on the "motherboard" that it
plugs into. This may mean removing the motherboard from the cabinet,
which is generally a giant PITA. I know *you* would never run the mill
with the cabinet wide open, but you have no idea what the low-down
so-and-so who owned it before you did.

I like Cydrome Leader's idea of possible bad solder joints. It could
also be that the edge connector on the motherboard has one or more
contacts that have lost their springiness. This is partly determined by
eliminating other causes, but if there are other cards with the same
connector, you can get an idea by unplugging one of those cards from its
slot and reseating it. Compare the force it takes to do that with the
force it takes to do the same thing with the problem board. If the
problem board is way easier to remove and replace, you might suspect the
connector. If you conclude that the connector is bad, usually you can
replace just the connector, but this may involve unsoldering a bunch of
pins.

If it's a bad connection, you might be able to induce the problem by
poking at the board(s) with a nice long dry plastic stick, as long as
you're reasonably sure that there isn't 120 V or 240 V running around
the board. Have a hand on the e-stop and/or circuit breaker when you do
this, just in case you manage to send a signal for "drive the table 20
feet that way and turn on the spindle to 100,000 rpm" by poking.

If I turn off the machine and let it cool for even 4 hours the board
will still throw alarms. However, if I remove the board and put it
back in the alarms stop.


If removing and reseating the board is an instant fix, I think this
points heavily in the direction of a bad contact somewhere. If you had
a failing component, usually you would have to wait for that component
to cool down enough to start working again.

I like this idea less, but here it is: if the sensor is a relatively
high-resistance device, a couple of things could be happening. 1) Some
foreign glop on the board in exactly the right (wrong?) spot has
changing resistance with temperature, and eventually gets low or high
enough to trigger the alarm. This wouldn't tend to go away just by
unplugging/replugging, though. 2) The alarm input, itself, has a high
impedance, and eventually drifts to a high enough voltage to trigger
the alarm. This *might* fix itself by unplugging/replugging.

Sometimes if there is a sensor that your model doesn't have, the input
for that sensor will have a jumper wire or resistor across it as a
dummy. Can you tell if anything like that used to be there and is now
missing? You might have to compare to photos of a similar machine -
this may or may not be in the manual.

I have cleaned the contacts with alcohol and "contact cleaner".


You might try taking the problem board out of the machine and sticking a
clean piece of stiff paper, like a folded index card, into the slot in
the edge connector that is still in the machine. Cut the paper to the
same length as the card edge connector - don't use a shorter piece of
paper and slide it back and forth, because you may catch one of the
contacts and bend it. It may also help to wrap the paper around a thin
piece of material (sheet metal?) - but you want the whole stack to be no
thicker than the circuit board that belongs there. Remove the paper and
inspect for signs of glop or corrosion in the edge connector.

So after the long winded explanation above I am wondering if dirty
contacts could somehow make the board run warm and cause the alarms.


Dirty contacts will heat up if there is enough current going through
them. However, I would guess that a board that monitors pressure
sensors (and probably interlock switches and stuff like that too) is
running on relatively low voltage and current. If there was a board
driving the servo motors or coolant pump or something that takes
relatively more juice, then it would have a worse time with dirty
contacts.

If you can identify the low-voltage DC power supply (probably 5, 12,
or 24 VDC, but it could be a lot of things), it probably wouldn't hurt
to measure its output voltages with a multimeter, both when the mill
is working OK and when it is throwing alarms. This probably isn't the
problem, but low (or high) power supplies can cause many weird effects.

Matt Roberds

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Old March 19th 14, 04:40 PM posted to sci.electronics.repair
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Posts: 2,099
Default A sign of dirty connectors?

On Wed, 19 Mar 2014 01:34:05 +0000 (UTC), wrote:

wrote:
One of my CNC mills has a problem. The machine, a Fadal 15XT, built in
1998, (I think), keeps showing an alarm for a malfunction the machine
can't have.


Does the problem board have any mechanical support other than the edge
connector? Is this support aligned correctly and connected? (Example:
the bracket on most PC expansion cards that screws down to the chassis.)


The board is properly supported.


You might also look for metal debris, oil, old grease, dried coolant,
etc, on both sides of the problem board and on the "motherboard" that it
plugs into. This may mean removing the motherboard from the cabinet,
which is generally a giant PITA. I know *you* would never run the mill
with the cabinet wide open, but you have no idea what the low-down
so-and-so who owned it before you did.


The board and the inside of the cabinet is clean. I have been running
the machine with the cabinet open though, just to get a couple jobs
done. I have made sure that nothing can get inside when open.

I like Cydrome Leader's idea of possible bad solder joints. It could
also be that the edge connector on the motherboard has one or more
contacts that have lost their springiness. This is partly determined by
eliminating other causes, but if there are other cards with the same
connector, you can get an idea by unplugging one of those cards from its
slot and reseating it. Compare the force it takes to do that with the
force it takes to do the same thing with the problem board. If the
problem board is way easier to remove and replace, you might suspect the
connector. If you conclude that the connector is bad, usually you can
replace just the connector, but this may involve unsoldering a bunch of
pins.

I'll try the card swap to see if I can detect any differences. If the
connectors are less springy if I can't bend them back where they
belong I will unsolder the connector and replace it. Unfortunately the
board it plugs into is buried behind everything else and will take a
lot of time to remove. And there 100 contacts in the edge connector.
I carefully inspected, with a 10x magnifier, the board for any bad
solder joints or cracked traces and found none.

If it's a bad connection, you might be able to induce the problem by
poking at the board(s) with a nice long dry plastic stick, as long as
you're reasonably sure that there isn't 120 V or 240 V running around
the board. Have a hand on the e-stop and/or circuit breaker when you do
this, just in case you manage to send a signal for "drive the table 20
feet that way and turn on the spindle to 100,000 rpm" by poking.

If I turn off the machine and let it cool for even 4 hours the board
will still throw alarms. However, if I remove the board and put it
back in the alarms stop.


If removing and reseating the board is an instant fix, I think this
points heavily in the direction of a bad contact somewhere. If you had
a failing component, usually you would have to wait for that component
to cool down enough to start working again.

Looking at the connector contacts on the board I can see that some
have more obvious marks than others on them from the contacts in the
female connector. Hmmm.

I like this idea less, but here it is: if the sensor is a relatively
high-resistance device, a couple of things could be happening. 1) Some
foreign glop on the board in exactly the right (wrong?) spot has
changing resistance with temperature, and eventually gets low or high
enough to trigger the alarm. This wouldn't tend to go away just by
unplugging/replugging, though. 2) The alarm input, itself, has a high
impedance, and eventually drifts to a high enough voltage to trigger
the alarm. This *might* fix itself by unplugging/replugging.

There is no foreign matter of any kind on the board and the machine
has no sensors. This is why the alarm is spurious. Could failing caps
be causing problems? Could unplugging the board allow some caps to
discharge which then makes the alarm go away?

Sometimes if there is a sensor that your model doesn't have, the input
for that sensor will have a jumper wire or resistor across it as a
dummy. Can you tell if anything like that used to be there and is now
missing? You might have to compare to photos of a similar machine -
this may or may not be in the manual.

I'll see what I can figure out about what may be different on this
board from one in a machine equipped with sensors.

I have cleaned the contacts with alcohol and "contact cleaner".


You might try taking the problem board out of the machine and sticking a
clean piece of stiff paper, like a folded index card, into the slot in
the edge connector that is still in the machine. Cut the paper to the
same length as the card edge connector - don't use a shorter piece of
paper and slide it back and forth, because you may catch one of the
contacts and bend it. It may also help to wrap the paper around a thin
piece of material (sheet metal?) - but you want the whole stack to be no
thicker than the circuit board that belongs there. Remove the paper and
inspect for signs of glop or corrosion in the edge connector.

I'll try your folded paper cleaning strategy and report back.

So after the long winded explanation above I am wondering if dirty
contacts could somehow make the board run warm and cause the alarms.


Dirty contacts will heat up if there is enough current going through
them. However, I would guess that a board that monitors pressure
sensors (and probably interlock switches and stuff like that too) is
running on relatively low voltage and current. If there was a board
driving the servo motors or coolant pump or something that takes
relatively more juice, then it would have a worse time with dirty
contacts.

If you can identify the low-voltage DC power supply (probably 5, 12,
or 24 VDC, but it could be a lot of things), it probably wouldn't hurt
to measure its output voltages with a multimeter, both when the mill
is working OK and when it is throwing alarms. This probably isn't the
problem, but low (or high) power supplies can cause many weird effects.

Matt Roberds

Thanks for the suggestions Matt.
Eric

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Old March 19th 14, 04:45 PM posted to sci.electronics.repair
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Default A sign of dirty connectors?

On Tue, 18 Mar 2014 23:02:44 -0500, Jon Elson
wrote:

wrote:

Greetings All,
One of my CNC mills has a problem. The machine, a Fadal 15XT, built in
1998, (I think), keeps showing an alarm for a malfunction the machine
can't have.

Likely there is a rack of opto-coupled sensor modules. The lube and air
pressure sensor positions have likely been dummied out with jumper
wires. The symptom you describe is typical of a worn-out opto-coupler
where the LED light output is dying from being lit for 15 years. If
you can figure out which input coupler is the one for these functions,
you can probably just replace them. PLCcenter is a great resource
for all sorts of obscure Japanese components like this.

Jon

Greetings Jon,
There are opto-coupled boards in the machine but none on this board.
The Fadal repair folks told me this board is the interface board and
is probably the problem and since removing and replacing it stops the
alarm every time I think they are probably correct. However, I will
try to identify what all the opto-couplers do and see if any of them
are for the sensors that are not there.
Eric

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Old March 19th 14, 11:06 PM posted to sci.electronics.repair
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Posts: 686
Default A sign of dirty connectors?

On 3/19/2014 10:45 AM, wrote:
On Tue, 18 Mar 2014 23:02:44 -0500, Jon Elson
wrote:

wrote:

Greetings All,
One of my CNC mills has a problem. The machine, a Fadal 15XT, built in
1998, (I think), keeps showing an alarm for a malfunction the machine
can't have.

Likely there is a rack of opto-coupled sensor modules. The lube and air
pressure sensor positions have likely been dummied out with jumper
wires. The symptom you describe is typical of a worn-out opto-coupler
where the LED light output is dying from being lit for 15 years. If
you can figure out which input coupler is the one for these functions,
you can probably just replace them. PLCcenter is a great resource
for all sorts of obscure Japanese components like this.

Jon

Greetings Jon,
There are opto-coupled boards in the machine but none on this board.
The Fadal repair folks told me this board is the interface board and
is probably the problem and since removing and replacing it stops the
alarm every time I think they are probably correct. However, I will
try to identify what all the opto-couplers do and see if any of them
are for the sensors that are not there.
Eric

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I'm surprised no one has suggested a can of freeze mist.
When the alarm goes off, spray half the board to cool it down, then do
what ever is needed, restart the machine, reset the alarm, and see if
the alarm is still on. If it is on, spray the there half and test again.
Hopefully the alarm will have stopped, the next time the alarm starts,
spray 1/2 of the 1/2 that you sprayed before when the alarm stopped.
Now, if this is actually stopping the alarm, just continue limiting
the area until your down to a single part.
Mikek
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Old March 19th 14, 11:44 PM posted to sci.electronics.repair
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Posts: 2,099
Default A sign of dirty connectors?

On Wed, 19 Mar 2014 17:06:45 -0500, amdx wrote:

On 3/19/2014 10:45 AM, wrote:
On Tue, 18 Mar 2014 23:02:44 -0500, Jon Elson
wrote:

wrote:

Greetings All,
One of my CNC mills has a problem. The machine, a Fadal 15XT, built in
1998, (I think), keeps showing an alarm for a malfunction the machine
can't have.
Likely there is a rack of opto-coupled sensor modules. The lube and air
pressure sensor positions have likely been dummied out with jumper
wires. The symptom you describe is typical of a worn-out opto-coupler
where the LED light output is dying from being lit for 15 years. If
you can figure out which input coupler is the one for these functions,
you can probably just replace them. PLCcenter is a great resource
for all sorts of obscure Japanese components like this.

Jon

Greetings Jon,
There are opto-coupled boards in the machine but none on this board.
The Fadal repair folks told me this board is the interface board and
is probably the problem and since removing and replacing it stops the
alarm every time I think they are probably correct. However, I will
try to identify what all the opto-couplers do and see if any of them
are for the sensors that are not there.
Eric

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I'm surprised no one has suggested a can of freeze mist.
When the alarm goes off, spray half the board to cool it down, then do
what ever is needed, restart the machine, reset the alarm, and see if
the alarm is still on. If it is on, spray the there half and test again.
Hopefully the alarm will have stopped, the next time the alarm starts,
spray 1/2 of the 1/2 that you sprayed before when the alarm stopped.
Now, if this is actually stopping the alarm, just continue limiting
the area until your down to a single part.
Mikek

I have been using freeze spray but the results have been variable. So
I'm instead going to try a heat gun to saee if I can get the board to
fail faster.
Eric

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Old March 20th 14, 01:29 AM posted to sci.electronics.repair
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Posts: 182
Default A sign of dirty connectors?

wrote:
I'll try the card swap to see if I can detect any differences.


If you put a different card in the slot where the problem card goes, it
may or may not work - it isn't a given that all the slots on the
motherboard are the same. But you can at least judge the mechanical
condition of the connector that way. If you do this swap, do it with
*all* power to the mill shut off. (The different slots may have power
and ground on different pins...)

Unfortunately the board it plugs into is buried behind everything else
and will take a lot of time to remove.


That's usually how it is.

Looking at the connector contacts on the board I can see that some
have more obvious marks than others on them from the contacts in the
female connector. Hmmm.


They all should have some kind of mark, and it's normal for the marks to
vary a little. If most of the marks are obvious - dug into the copper/
gold somewhat, but a few of them you have to get out the 250 W lamp to
see the mark, then that's a clue.

Could failing caps be causing problems?


Possibly.

Could unplugging the board allow some caps to discharge which then
makes the alarm go away?


Kind of strange, but within the realm of possibility.

I'll try your folded paper cleaning strategy and report back.


OK. I will post to your new thread shortly as well.

Matt Roberds



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