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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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#1
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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 |
#2
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#4
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#5
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Franc Zabkar wrote:
On Mon, 05 Mar 2012 17:17:26 -0800, put finger to keyboard and composed: I can post pictures, but where? Some people use file hosting/sharing sites such as ImageShack. My ISP gives me my own free web space, as do most ISPs in Australia. Is this not the norm in the rest of the world? Just curious ... - Franc Zabkar I think many don't know to FTP, and use a picture program to generate thumbnails. Comcast gives you 10 gb. Never had a ISP not provide some kind of space. Greg |
#6
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#7
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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. |
#8
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![]() "nesesu" wrote in message news:8313557.1551.1331053301801.JavaMail.geo-discussion-forums@pbcgj3... 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. |
#9
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#10
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![]() "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 |
#11
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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 |
#12
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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 |
#13
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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. |
#14
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#15
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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 |
#16
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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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