Home |
Search |
Today's Posts |
|
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. |
Reply |
|
LinkBack | Thread Tools | Display Modes |
#1
Posted to sci.electronics.repair,comp.sys.intel
|
|||
|
|||
Contact resistance in ATX power connectors causing grief
Hello folks,
I am having a rather unusual problem with about six hundred embedded motherboards in the field, and was hoping someone might have an idea (or two) on what might be happening, and possibly what the fix might be. These are embedded low power Via C3 based motherboards that are deployed in the factory automation industry. Power is distributed from the power supply to the motherboard through a 12" power cable which consists of (2) 18ga. ground wires and (2) 18ga. +5VDC wires to an ATX style connector on the motherboard; the board draws about 3 amps of +5VDC under maximum CPU load. After several months in the field, contact resistance on the ATX connector increases for some reason, and is causing a voltage drop as seen on the motherboard (sometimes as much as .5VDC!) There is an onboard voltage monitor on the CPU board that triggers a reset at about 4.7VDC, the end result being that the processor gets stuck in a reset loop - it will run for a minute or so and then the CPU load momentarily increases and resets again. The voltage drop is *usually* greater across the ground lines than the +5 lines for some reason. Maybe there's a clue there? On a system that is failing, unplugging the ATX connector and reseating it will "fix" the problem and the system will continue to work for several months until once again the resistance increases in the contacts and... well, you get the picture. If the connector is reseated here at the factory and "repaired", we cannot get it to fail again under any conditions: vibration, humidity, temperature cycling in a environmental chamber, etc. We've tried using contact lube - no luck. Thinking that there might be a problem with dissimilar metals, we checked that the contacts on the cable and ATX connector on the board are tin. The contact specification claims that they are gas tight. At first (a number of months ago) we were seeing only a .2 to .3VDC drop, so we increased the power supplies output to 5.15VDC hoping to compensate for the drop (a Band-aide, I know), but as you can see above, the contact resistance kept increasing only to have the same problem occur. We cannot increase the gauge of the wire, nor can we add more +5 and ground wires due to there being only 2 pins available for each on the power supply. The crimps will not accept double crimping. I know the problem could be solved by soldering the wires between the power supply and MB, but this would be a huge task due to the number of units in the field, and the difficulty of disassembling the systems, pulling the boards, and reworking them. Does anyone have any thoughts on what is happening here, and possibly an easier solution? Thanks very much for any help. |
#2
Posted to sci.electronics.repair,comp.sys.intel
|
|||
|
|||
Contact resistance in ATX power connectors causing grief
Jay W. wrote:
Hello folks, I am having a rather unusual problem with about six hundred embedded motherboards in the field, and was hoping someone might have an idea (or two) on what might be happening, and possibly what the fix might be. What is the response from the motherboard manufacturers? Have you approached them? These are embedded low power Via C3 based motherboards that are deployed in the factory automation industry. Power is distributed from the power supply to the motherboard through a 12" power cable which consists of (2) 18ga. ground wires and (2) 18ga. +5VDC wires to an ATX style connector on the motherboard; the board draws about 3 amps of +5VDC under maximum CPU load. After several months in the field, contact resistance on the ATX connector increases for some reason, and is causing a voltage drop as seen on the motherboard (sometimes as much as .5VDC!) There is an onboard voltage monitor on the CPU board that triggers a reset at about 4.7VDC, the end result being that the processor gets stuck in a reset loop - it will run for a minute or so and then the CPU load momentarily increases and resets again. The voltage drop is *usually* greater across the ground lines than the +5 lines for some reason. Maybe there's a clue there? Hmmm, there is more current on the return from motherboard ground back to the supply (roughly equal to sum of currents in 5V, 3.3V and 12V rails) but I'd expect some of this to also travel back to the PSU through motherboard ground contact points (screws) and the metal case of the PSU. Check those grounding points? -- Adrian C |
#3
Posted to sci.electronics.repair,comp.sys.intel
|
|||
|
|||
Contact resistance in ATX power connectors causing grief
What chemicals are these guys using in their factory? I'd lay some guesses
that there's something "horrid" flying around in either vapour or droplet form. Is that all hapening at one clients? Dave "Jay W." wrote in message news Hello folks, I am having a rather unusual problem with about six hundred embedded motherboards in the field, and was hoping someone might have an idea (or two) on what might be happening, and possibly what the fix might be. These are embedded low power Via C3 based motherboards that are deployed in the factory automation industry. Power is distributed from the power supply to the motherboard through a 12" power cable which consists of (2) 18ga. ground wires and (2) 18ga. +5VDC wires to an ATX style connector on the motherboard; the board draws about 3 amps of +5VDC under maximum CPU load. After several months in the field, contact resistance on the ATX connector increases for some reason, and is causing a voltage drop as seen on the motherboard (sometimes as much as .5VDC!) There is an onboard voltage monitor on the CPU board that triggers a reset at about 4.7VDC, the end result being that the processor gets stuck in a reset loop - it will run for a minute or so and then the CPU load momentarily increases and resets again. The voltage drop is *usually* greater across the ground lines than the +5 lines for some reason. Maybe there's a clue there? On a system that is failing, unplugging the ATX connector and reseating it will "fix" the problem and the system will continue to work for several months until once again the resistance increases in the contacts and... well, you get the picture. If the connector is reseated here at the factory and "repaired", we cannot get it to fail again under any conditions: vibration, humidity, temperature cycling in a environmental chamber, etc. We've tried using contact lube - no luck. Thinking that there might be a problem with dissimilar metals, we checked that the contacts on the cable and ATX connector on the board are tin. The contact specification claims that they are gas tight. At first (a number of months ago) we were seeing only a .2 to .3VDC drop, so we increased the power supplies output to 5.15VDC hoping to compensate for the drop (a Band-aide, I know), but as you can see above, the contact resistance kept increasing only to have the same problem occur. We cannot increase the gauge of the wire, nor can we add more +5 and ground wires due to there being only 2 pins available for each on the power supply. The crimps will not accept double crimping. I know the problem could be solved by soldering the wires between the power supply and MB, but this would be a huge task due to the number of units in the field, and the difficulty of disassembling the systems, pulling the boards, and reworking them. Does anyone have any thoughts on what is happening here, and possibly an easier solution? Thanks very much for any help. |
#4
Posted to sci.electronics.repair,comp.sys.intel
|
|||
|
|||
Contact resistance in ATX power connectors causing grief
"Jay W." wrote in message news Thinking that there might be a problem with dissimilar metals, we checked that the contacts on the cable and ATX connector on the board are tin. The contact specification claims that they are gas tight. Gas tight? Any chance that moisture is being trapped inside on assembly? Dave |
#5
Posted to sci.electronics.repair,comp.sys.intel
|
|||
|
|||
Contact resistance in ATX power connectors causing grief
In article , Jay W. wrote:
Hello folks, I am having a rather unusual problem with about six hundred embedded motherboards in the field, and was hoping someone might have an idea (or two) on what might be happening, and possibly what the fix might be. These are embedded low power Via C3 based motherboards that are deployed in the factory automation industry. Power is distributed from the power supply to the motherboard through a 12" power cable which consists of (2) 18ga. ground wires and (2) 18ga. +5VDC wires to an ATX style connector on the motherboard; the board draws about 3 amps of +5VDC under maximum CPU load. After several months in the field, contact resistance on the ATX connector increases for some reason, and is causing a voltage drop as seen on the motherboard (sometimes as much as .5VDC!) There is an onboard voltage monitor on the CPU board that triggers a reset at about 4.7VDC, the end result being that the processor gets stuck in a reset loop - it will run for a minute or so and then the CPU load momentarily increases and resets again. The voltage drop is *usually* greater across the ground lines than the +5 lines for some reason. Maybe there's a clue there? On a system that is failing, unplugging the ATX connector and reseating it will "fix" the problem and the system will continue to work for several months until once again the resistance increases in the contacts and... well, you get the picture. If the connector is reseated here at the factory and "repaired", we cannot get it to fail again under any conditions: vibration, humidity, temperature cycling in a environmental chamber, etc. We've tried using contact lube - no luck. What kind?? In tough spots I grab my old Cramolin vial, and or Tweek or Stabilant. The pure form of Deoxit in the tube, or Caig greese would do. And have you tried tightening the female contact going to the board. I suppose the female pin is crimped to the wire, could be faulty crimp, of course many crimps are faulty from the getgo. Thinking that there might be a problem with dissimilar metals, we checked that the contacts on the cable and ATX connector on the board are tin. The contact specification claims that they are gas tight. At first (a number of months ago) we were seeing only a .2 to .3VDC drop, so we increased the power supplies output to 5.15VDC hoping to compensate for the drop (a Band-aide, I know), but as you can see above, the contact resistance kept increasing only to have the same problem occur. We cannot increase the gauge of the wire, nor can we add more +5 and ground wires due to there being only 2 pins available for each on the power supply. The crimps will not accept double crimping. I know the problem could be solved by soldering the wires between the power supply and MB, but this would be a huge task due to the number of units in the field, and the difficulty of disassembling the systems, pulling the boards, and reworking them. Does anyone have any thoughts on what is happening here, and possibly an easier solution? Stop the fault from tripping the CPU. Bios? |
#6
Posted to sci.electronics.repair,comp.sys.intel
|
|||
|
|||
Contact resistance in ATX power connectors causing grief
Jay W. wrote:
Hello folks, I am having a rather unusual problem with about six hundred embedded motherboards in the field, and was hoping someone might have an idea (or two) on what might be happening, and possibly what the fix might be. These are embedded low power Via C3 based motherboards that are deployed in the factory automation industry. Power is distributed from the power supply to the motherboard through a 12" power cable which consists of (2) 18ga. ground wires and (2) 18ga. +5VDC wires to an ATX style connector on the motherboard; the board draws about 3 amps of +5VDC under maximum CPU load. After several months in the field, contact resistance on the ATX connector increases for some reason, and is causing a voltage drop as seen on the motherboard (sometimes as much as .5VDC!) There is an onboard voltage monitor on the CPU board that triggers a reset at about 4.7VDC, the end result being that the processor gets stuck in a reset loop - it will run for a minute or so and then the CPU load momentarily increases and resets again. The voltage drop is *usually* greater across the ground lines than the +5 lines for some reason. Maybe there's a clue there? On a system that is failing, unplugging the ATX connector and reseating it will "fix" the problem and the system will continue to work for several months until once again the resistance increases in the contacts and... well, you get the picture. If the connector is reseated here at the factory and "repaired", we cannot get it to fail again under any conditions: vibration, humidity, temperature cycling in a environmental chamber, etc. We've tried using contact lube - no luck. Thinking that there might be a problem with dissimilar metals, we checked that the contacts on the cable and ATX connector on the board are tin. The contact specification claims that they are gas tight. At first (a number of months ago) we were seeing only a .2 to .3VDC drop, so we increased the power supplies output to 5.15VDC hoping to compensate for the drop (a Band-aide, I know), but as you can see above, the contact resistance kept increasing only to have the same problem occur. We cannot increase the gauge of the wire, nor can we add more +5 and ground wires due to there being only 2 pins available for each on the power supply. The crimps will not accept double crimping. I know the problem could be solved by soldering the wires between the power supply and MB, but this would be a huge task due to the number of units in the field, and the difficulty of disassembling the systems, pulling the boards, and reworking them. Does anyone have any thoughts on what is happening here, and possibly an easier solution? Thanks very much for any help. Clearly it's environmental, since you can't get it to happen in the lab. This suggests something nasty in the environment. However, one thing you can check is if everything is properly grounded and you're not getting any ground loops. While it's unlikely, I can just barely envision the manipulation of replugging the connector regrounding the board. The term gas tight is reassuring, but I wouldn't take it on faith. If the failure vs. time is relatively constant, sealing the top and bottom of the connector would be an interesting data point. A bead around the bottom where the connector meets the board, and also one at the top where the wires enter the connector. If it's a unit assembly, can you shrink wrap where the cable enters the connector? Is there any visible change in the pins to indicate corrosion? -- -bill davidsen ) "The secret to procrastination is to put things off until the last possible moment - but no longer" -me |
#7
Posted to sci.electronics.repair,comp.sys.intel
|
|||
|
|||
Contact resistance in ATX power connectors causing grief
Jay W. hath wroth:
After several months in the field, contact resistance on the ATX connector increases for some reason, and is causing a voltage drop as seen on the motherboard (sometimes as much as .5VDC!) Are you sure it's the connector contact resistance and not the wire crimp on the ATX connector? I've seen something like this inside wafer fab tunnels, where the rather caustic chemicals attack the copper wire to solder plate junction on the connector pins. I've never seen a 0.5VDC drop. More like 200-300mv at worst. Egads, 0.5VDC at 3A is 1.5 watts. The ATX connector should melt with that much power being dissipated. Any discoloring of the nylon connector shell? On a system that is failing, unplugging the ATX connector and reseating it will "fix" the problem and the system will continue to work for several months until once again the resistance increases in the contacts and... well, you get the picture. Well, that certainly sounds like its the connector contact and not the crimp. However, I'm suspicious and will pretend that it might still be the crimp. Have you tried to take an ohms-guesser or ESR meter and measure the contact resistance (or crimp resistance) of the connections? Also, measure the voltage drop when running between: motherboard to ATX pin ATX pin to copper wire (across crimp) Case ground to motheboard ground (just for fun). Instead of removing and re-inserting the connector, can you get it to recover by merely wiggling the ATX connector from side to side, or doing the same with individual pins by wiggling the wires sideways? If yes, then you punching through a layer of surface crud, corrosion, oxidation, or chemical buildup of some sorts. If no, then inspect the crimp for insulation crimps, dissimilar metal issues, and corrosion. Any evidence of copper wire embrittlement at the crimp? Heating of the connection can do that. We've tried using contact lube - no luck. No. That's just solvent and light oil. Try Cramoline, De-Oxit or some oxidation prevention chemical. Also try grease or silicon grease. Anything to provide a seal. Thinking that there might be a problem with dissimilar metals, we checked that the contacts on the cable and ATX connector on the board are tin. The contact specification claims that they are gas tight. Gas tight over what area? Verify that you have a large mating surface area and not a tapered loose fit. I've seen connector tolerances create a loose connection that eventually fails. (Hint: I designed marine radios in a previous life). Sacrifice one power supply connector and remove the nylon shell with a pair of wire cutters. Do NOT use an extraction tool for this. Take each connection and *MEASURE* the insertion and extraction force. If the power supply manufacturers crimping machine screwed up the connector fit, you have a potential cause. Also, tin oxide is almost transparent and rather difficult to see. However, you can detect it with an ohms-guesser. Try passing the probe tips over the ATX plug surface, without punching through, and see if you get any insulated areas. I think the best approach is to identify whatever chemical is attacking the connectors. I'm not sure how to do this. Also, I'm not convinced that the connectors pins are as great as you claim. Are they tin, solder plate, or lead-free solder plate? If lead-free, what substitute solder plating are they using? -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#8
|
|||
|
|||
Quote:
|
#9
Posted to sci.electronics.repair,comp.sys.intel
|
|||
|
|||
Contact resistance in ATX power connectors causing grief
On Thu, 11 May 2006 06:18:28 -0400, Jay W. put
finger to keyboard and composed: Hello folks, I am having a rather unusual problem with about six hundred embedded motherboards in the field, and was hoping someone might have an idea (or two) on what might be happening, and possibly what the fix might be. These are embedded low power Via C3 based motherboards that are deployed in the factory automation industry. Power is distributed from the power supply to the motherboard through a 12" power cable which consists of (2) 18ga. ground wires and (2) 18ga. +5VDC wires to an ATX style connector on the motherboard; the board draws about 3 amps of +5VDC under maximum CPU load. After several months in the field, contact resistance on the ATX connector increases for some reason, and is causing a voltage drop as seen on the motherboard (sometimes as much as .5VDC!) There is an onboard voltage monitor on the CPU board that triggers a reset at about 4.7VDC, the end result being that the processor gets stuck in a reset loop - it will run for a minute or so and then the CPU load momentarily increases and resets again. The voltage drop is *usually* greater across the ground lines than the +5 lines for some reason. Maybe there's a clue there? On a system that is failing, unplugging the ATX connector and reseating it will "fix" the problem and the system will continue to work for several months until once again the resistance increases in the contacts and... well, you get the picture. If the connector is reseated here at the factory and "repaired", we cannot get it to fail again under any conditions: vibration, humidity, temperature cycling in a environmental chamber, etc. We've tried using contact lube - no luck. If it's an environmental issue, try flooding the connector with the same gel (?) that telco's use for their wire joins. Or try vaseline. - Franc Zabkar -- Please remove one 'i' from my address when replying by email. |
#10
Posted to sci.electronics.repair,comp.sys.intel
|
|||
|
|||
Contact resistance in ATX power connectors causing grief
Just a thought, I imagine each embedded motherboard has several other
connectors (IDE, fan, whatever). If it's a environmental problem like a lot of people seem to think it is, shouldn't all the connectors be failing? Lance ***** Jay W. thought carefully and wrote on 5/11/2006 3:18 AM: Hello folks, I am having a rather unusual problem with about six hundred embedded motherboards in the field, and was hoping someone might have an idea (or two) on what might be happening, and possibly what the fix might be. These are embedded low power Via C3 based motherboards that are deployed in the factory automation industry. Power is distributed from the power supply to the motherboard through a 12" power cable which consists of (2) 18ga. ground wires and (2) 18ga. +5VDC wires to an ATX style connector on the motherboard; the board draws about 3 amps of +5VDC under maximum CPU load. After several months in the field, contact resistance on the ATX connector increases for some reason, and is causing a voltage drop as seen on the motherboard (sometimes as much as .5VDC!) There is an onboard voltage monitor on the CPU board that triggers a reset at about 4.7VDC, the end result being that the processor gets stuck in a reset loop - it will run for a minute or so and then the CPU load momentarily increases and resets again. The voltage drop is *usually* greater across the ground lines than the +5 lines for some reason. Maybe there's a clue there? On a system that is failing, unplugging the ATX connector and reseating it will "fix" the problem and the system will continue to work for several months until once again the resistance increases in the contacts and... well, you get the picture. If the connector is reseated here at the factory and "repaired", we cannot get it to fail again under any conditions: vibration, humidity, temperature cycling in a environmental chamber, etc. We've tried using contact lube - no luck. Thinking that there might be a problem with dissimilar metals, we checked that the contacts on the cable and ATX connector on the board are tin. The contact specification claims that they are gas tight. At first (a number of months ago) we were seeing only a .2 to .3VDC drop, so we increased the power supplies output to 5.15VDC hoping to compensate for the drop (a Band-aide, I know), but as you can see above, the contact resistance kept increasing only to have the same problem occur. We cannot increase the gauge of the wire, nor can we add more +5 and ground wires due to there being only 2 pins available for each on the power supply. The crimps will not accept double crimping. I know the problem could be solved by soldering the wires between the power supply and MB, but this would be a huge task due to the number of units in the field, and the difficulty of disassembling the systems, pulling the boards, and reworking them. Does anyone have any thoughts on what is happening here, and possibly an easier solution? Thanks very much for any help. |
#11
Posted to sci.electronics.repair,comp.sys.intel
|
|||
|
|||
Contact resistance in ATX power connectors causing grief
On Fri, 12 May 2006 07:39:16 +1000, Franc Zabkar
wrote: On Thu, 11 May 2006 06:18:28 -0400, Jay W. put finger to keyboard and composed: Hello folks, We've tried using contact lube - no luck. If it's an environmental issue, try flooding the connector with the same gel (?) that telco's use for their wire joins. Or try vaseline. - Franc Zabkar -- Please remove one 'i' from my address when replying by email. Agreed, silicone grease fill the ATX female and fill the male side as well, this will be messy but should stop the corrsion. On next design, make sure the crimped connections are CORRECT or use screw terminals, preferably. ITC0008 pincushion thick 3 wire plugs had mis-match gauge crimp that it is just enough to develop resistance over time or tin pins/contacts corroding. Soldering wires directly to PCB was the solution on ITC008. Cheers, Wizard |
#12
Posted to sci.electronics.repair,comp.sys.intel
|
|||
|
|||
Contact resistance in ATX power connectors causing grief
On Fri, 12 May 2006 00:36:29 GMT, Lance
wrote: Just a thought, I imagine each embedded motherboard has several other connectors (IDE, fan, whatever). If it's a environmental problem like a lot of people seem to think it is, shouldn't all the connectors be failing? No. The ones carrying high currents will tend to fail first. Also, connectors that carry very little current can tolerate far more contact resistance than connectors that carry high currents. -- # Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060 # 831-336-2558 # http://802.11junk.com # http://www.LearnByDestroying.com AE6KS |
#13
Posted to sci.electronics.repair,comp.sys.intel
|
|||
|
|||
Contact resistance in ATX power connectors causing grief
On Fri, 12 May 2006 00:36:29 GMT, Lance
wrote: Just a thought, I imagine each embedded motherboard has several other connectors (IDE, fan, whatever). If it's a environmental problem like a lot of people seem to think it is, shouldn't all the connectors be failing? Lance ***** Probably right Lance, but maybe a bit of extra resistance does not matter so critically in all circuits. Also the discussion has not mentioned the necessity for good mechanical pressure in the connectors. I had extensive problems with otherwise good connectors in another set up where the spring fingers were not having or retaining their intended springiness. Also the contact material may not be as good or pure as hoped for. Peter Dettmann |
#14
Posted to sci.electronics.repair,comp.sys.intel
|
|||
|
|||
Contact resistance in ATX power connectors causing grief
Peter Dettmann hath wroth:
Also the discussion has not mentioned the necessity for good mechanical pressure in the connectors. I had extensive problems with otherwise good connectors in another set up where the spring fingers were not having or retaining their intended springiness. Also the contact material may not be as good or pure as hoped for. Peter Dettmann Someone most certainly did mention mechanical pressure, which methinks is a big part of the problem. See: http://groups.google.com/group/comp....cd035216258215 starting with "Gas tight over what area...". I recommended he sacrifice one power supply connector end and measure the retention and extraction force on the mating connectors without the shell. My guess(tm) is that they're fairly loose. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#15
Posted to sci.electronics.repair,comp.sys.intel
|
|||
|
|||
Contact resistance in ATX power connectors causing grief
On Sat, 13 May 2006 09:06:04 -0700, Jeff Liebermann
wrote: Peter Dettmann hath wroth: Also the discussion has not mentioned the necessity for good mechanical pressure in the connectors. I had extensive problems with otherwise good connectors in another set up where the spring fingers were not having or retaining their intended springiness. Also the contact material may not be as good or pure as hoped for. Peter Dettmann Someone most certainly did mention mechanical pressure, which methinks is a big part of the problem. See: http://groups.google.com/group/comp....cd035216258215 starting with "Gas tight over what area...". I recommended he sacrifice one power supply connector end and measure the retention and extraction force on the mating connectors without the shell. My guess(tm) is that they're fairly loose. Great Jeff, I missed that, but agree with your analysis. Peter Dettmann |
#16
Posted to sci.electronics.repair,comp.sys.intel
|
|||
|
|||
Contact resistance in ATX power connectors causing grief
It sounds as though the females are shoddy; perhaps losing their
springiness and becoming loose. I'd suggest getting new sockets and shrouds from Molex or similar and equip them with 6" pigtails. In the field, cut off the defective females and splice the new pigtails on. (Or a bit more expensive but saving you labor, buy extension cords with suitable connectors and discard the end you don't need.) Jay W. wrote: Hello folks, I am having a rather unusual problem with about six hundred embedded motherboards in the field, and was hoping someone might have an idea (or two) on what might be happening, and possibly what the fix might be. These are embedded low power Via C3 based motherboards that are deployed in the factory automation industry. Power is distributed from the power supply to the motherboard through a 12" power cable which consists of (2) 18ga. ground wires and (2) 18ga. +5VDC wires to an ATX style connector on the motherboard; the board draws about 3 amps of +5VDC under maximum CPU load. After several months in the field, contact resistance on the ATX connector increases for some reason, and is causing a voltage drop as seen on the motherboard (sometimes as much as .5VDC!) There is an onboard voltage monitor on the CPU board that triggers a reset at about 4.7VDC, the end result being that the processor gets stuck in a reset loop - it will run for a minute or so and then the CPU load momentarily increases and resets again. The voltage drop is *usually* greater across the ground lines than the +5 lines for some reason. Maybe there's a clue there? On a system that is failing, unplugging the ATX connector and reseating it will "fix" the problem and the system will continue to work for several months until once again the resistance increases in the contacts and... well, you get the picture. If the connector is reseated here at the factory and "repaired", we cannot get it to fail again under any conditions: vibration, humidity, temperature cycling in a environmental chamber, etc. We've tried using contact lube - no luck. Thinking that there might be a problem with dissimilar metals, we checked that the contacts on the cable and ATX connector on the board are tin. The contact specification claims that they are gas tight. At first (a number of months ago) we were seeing only a .2 to .3VDC drop, so we increased the power supplies output to 5.15VDC hoping to compensate for the drop (a Band-aide, I know), but as you can see above, the contact resistance kept increasing only to have the same problem occur. We cannot increase the gauge of the wire, nor can we add more +5 and ground wires due to there being only 2 pins available for each on the power supply. The crimps will not accept double crimping. I know the problem could be solved by soldering the wires between the power supply and MB, but this would be a huge task due to the number of units in the field, and the difficulty of disassembling the systems, pulling the boards, and reworking them. Does anyone have any thoughts on what is happening here, and possibly an easier solution? Thanks very much for any help. |
Reply |
Thread Tools | Search this Thread |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Forum | |||
Brown's gas?? | Metalworking | |||
Strange power problem with Sharp Mid-Drive VCR VC-H86 | Electronics Repair | |||
Power Supply Repair | Electronics Repair | |||
Power surges 1/ 2 | Home Repair |