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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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completely nonserviceable power supplies
I love switching power supplies where every ****ing part is under or
completely surrounded by some sort of obnoxious glue or potting compound. I've got a fairly expensive-ish cisco switch here going to the trash heap as the single output power supply cannot be worked on at all. replacements are over $400, even on ebay, so screw that. **** you lite-on. I should make it a point to dump this **** back in the stream behind the chinese factory that made this stuff in the first place. They did take the time to silkscreen something about using on the correct fuses, but even this is under like 13 screws and silcone gunk. |
#2
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completely nonserviceable power supplies
Cydrome Leader wrote in message
... I love switching power supplies where every ****ing part is under or completely surrounded by some sort of obnoxious glue or potting compound. I've got a fairly expensive-ish cisco switch here going to the trash heap as the single output power supply cannot be worked on at all. replacements are over $400, even on ebay, so screw that. **** you lite-on. I should make it a point to dump this **** back in the stream behind the chinese factory that made this stuff in the first place. They did take the time to silkscreen something about using on the correct fuses, but even this is under like 13 screws and silcone gunk. At least with all the cheap skating these days, they user a lot of chalk filler in epoxy type potting and with a bit of time can be mechanically/thermally excavated if the time is worth it. After the first one you have a good idea where the vulnerable parts are |
#3
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completely nonserviceable power supplies
"Cydrome Leader" I love switching power supplies where every ****ing part is under or completely surrounded by some sort of obnoxious glue or potting compound. I've got a fairly expensive-ish cisco switch here going to the trash heap as the single output power supply cannot be worked on at all. ** Still not as bad as the infamous, corrosive "yellow glue" that literally eats components right off the PCB. Been around since the 1980s and still going strong today. ...... Phil |
#4
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completely nonserviceable power supplies
On Fri, 11 May 2012 05:07:20 +0000 (UTC), Cydrome Leader
wrote: I love switching power supplies where every ****ing part is under or completely surrounded by some sort of obnoxious glue or potting compound. Unfortunately, the glue and goo are a necessary part of the design. The problem is that there are many parts in a switcher that mechanically vibrate at the switching frequency. If coupled through the pins to the PCB, it will soon produce an intermittent connection. I've seen transformers literally fall out of a PCB as the ultrasonic vibrations cold flowed the solder. I could see an annular ring around the pins. If I resoldered the pad, the problem would reappear in an accelerated burnin. There are also noise specifications which were difficult to meet with loose components, where the PCB acted like a sounding board. The glue and goo couple the component mechanical vibrations to the PCB, heatsink, case, or whatever. Distributing the load from a point source (wire leads) to a larger surface reduces the energy concentration and eliminates the cracked solder connection problem. RTV doesn't do this very well as it's elastic and does not couple mechanical energy very well. Epoxy works well because it's rigid. It also has a similar temperature coefficient to G10/FR4 PCB material, which prevents breaking the glue joint with temperature cycling. I've substituted power supplies inside various Cisco router in the distant past (2500/2600 series). It wasn't difficult finding a source. Make and model? -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#5
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completely nonserviceable power supplies
Jeff Liebermann wrote:
On Fri, 11 May 2012 05:07:20 +0000 (UTC), Cydrome Leader wrote: I love switching power supplies where every ****ing part is under or completely surrounded by some sort of obnoxious glue or potting compound. Unfortunately, the glue and goo are a necessary part of the design. The problem is that there are many parts in a switcher that mechanically vibrate at the switching frequency. If coupled through the pins to the PCB, it will soon produce an intermittent connection. I've seen transformers literally fall out of a PCB as the ultrasonic vibrations cold flowed the solder. I could see an annular ring around the pins. If I resoldered the pad, the problem would reappear in an accelerated burnin. There are also noise specifications which were difficult to meet with loose components, where the PCB acted like a sounding board. The glue and goo couple the component mechanical vibrations to the PCB, heatsink, case, or whatever. Distributing the load from a point source (wire leads) to a larger surface reduces the energy concentration and eliminates the cracked solder connection problem. RTV doesn't do this very well as it's elastic and does not couple mechanical energy very well. Epoxy works well because it's rigid. It also has a similar temperature coefficient to G10/FR4 PCB material, which prevents breaking the glue joint with temperature cycling. I've substituted power supplies inside various Cisco router in the distant past (2500/2600 series). It wasn't difficult finding a source. Make and model? In this case, none of the magnetics were glued, just stupid stuff like ICs, passives and resistors and junk like the fuse and MOV stuff. The switch was a 2700? series or whatever the gige ones were that were 1.5 U tall for 24 ports. The power supplies in this series were goofy, with nonstandard even for cisco RPS connectors. It's not something I'd take to a datacenter and run off some CB power supply with a few diodes. that series has been dropped for ones with slightly lower model numbers. The main board on the switch had all exploded caps in the DC to DC converter area, fixable with a really really really hot soldering iron. it's just not worth the effort to fix and sell stuff one-offs like this. |
#6
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completely nonserviceable power supplies
Just what does this thing put out in volts and amps ? How many
supplies does it have ? As far as I know a router has no motor or anything (well that kind of router), what could it possibly need that's so hard to come by ? If all it is is like 5 volts. plus and minus 12, maybe a 3.3, why not use a PC power supply ? What the hell is it about this things that it can't ? J |
#7
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completely nonserviceable power supplies
On May 12, 12:07*am, Jeff Urban wrote:
Just what does this thing put out in volts and amps ? How many supplies does it have ? As far as I know a router has no motor or anything (well that kind of router), what could it possibly need that's so hard to come by ? If all it is is like 5 volts. plus and minus 12, maybe a 3.3, why not use a PC power supply ? What the hell is it about this things that it can't ? J I agree. Can you determine where your voltages need to be and just "insert" them from a known good supply? The equipment shouldn't care where the DC comes from as long as it's there. Lenny |
#8
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completely nonserviceable power supplies
klem kedidelhopper wrote:
On May 12, 12:07?am, Jeff Urban wrote: Just what does this thing put out in volts and amps ? How many supplies does it have ? As far as I know a router has no motor or anything (well that kind of router), what could it possibly need that's so hard to come by ? If all it is is like 5 volts. plus and minus 12, maybe a 3.3, why not use a PC power supply ? What the hell is it about this things that it can't ? J I agree. Can you determine where your voltages need to be and just "insert" them from a known good supply? The equipment shouldn't care where the DC comes from as long as it's there. Lenny yes and no. I could run it forever with jumper cables to another power supply, but that's not acceptable in a datacenter. the unit has been trashed, I kept the blowers though. Chinese fans apparenly outlast chinese power supplies. |
#9
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completely nonserviceable power supplies
Cydrome Leader wrote in
: Chinese fans apparenly outlast chinese power supplies. understandable,....power supplies take a lot more stress. ;-) OR,the fans follow the KISS principle of engineering....and the Chinese PS follows it too far. ;-) -- Jim Yanik jyanik at localnet dot com |
#10
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completely nonserviceable power supplies
Jim Yanik wrote:
Cydrome Leader wrote in : Chinese fans apparenly outlast chinese power supplies. understandable,....power supplies take a lot more stress. ;-) OR,the fans follow the KISS principle of engineering....and the Chinese PS follows it too far. ;-) I guess to be fair, the fans are from NMB, and they know bearings. Lite-on makes third rate keyboards, cdroms and apparently power supplies. |
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