completely nonserviceable power supplies

C

Cydrome Leader

Guest
I love switching power supplies where every fucking 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.

fuck you lite-on. I should make it a point to dump this shit 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.
 
Cydrome Leader <presence@MUNGEpanix.com> wrote in message
news:joi6q8$7mt$1@reader1.panix.com...
I love switching power supplies where every fucking 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.

fuck you lite-on. I should make it a point to dump this shit 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.
Click to expand...

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
 
"Cydrome Leader"

I love switching power supplies where every fucking 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.
Click to expand...

** 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
 
On Fri, 11 May 2012 05:07:20 +0000 (UTC), Cydrome Leader
<presence@MUNGEpanix.com> wrote:

I love switching power supplies where every fucking part is under or
completely surrounded by some sort of obnoxious glue or potting compound.
Click to expand...
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 jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
 
Jeff Liebermann <jeffl@cruzio.com> wrote:
On Fri, 11 May 2012 05:07:20 +0000 (UTC), Cydrome Leader
presence@MUNGEpanix.com> wrote:

I love switching power supplies where every fucking 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?
Click to expand...
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.
 
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
 
On May 12, 12:07 am, Jeff Urban <jurb6...@gmail.com> 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
Click to expand...
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
 
klem kedidelhopper <captainvideo462009@gmail.com> wrote:
On May 12, 12:07?am, Jeff Urban <jurb6...@gmail.com> 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
Click to expand...
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.
 
Cydrome Leader <presence@MUNGEpanix.com> wrote in
news:jou0iv$42t$2@reader1.panix.com:

Chinese fans
apparenly outlast chinese power supplies.
Click to expand...
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
 
Jim Yanik <jyanik@abuse.gov> wrote:
Cydrome Leader <presence@MUNGEpanix.com> wrote in
news:jou0iv$42t$2@reader1.panix.com:

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. ;-)
Click to expand...
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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