On 05/04/2009 04:19 PM, David Liguori wrote:
Aldo Foot wrote:
On Wed, Apr 29, 2009 at 7:23 PM, Robert L Cochran
<cochranb@xxxxxxxxxxxxx> wrote:
Has the device firmware been pharmed or simply partly flashed and
then a
power failure struck?
If you would like to donate the unit to me, I'll try to find the
time to
take a look at it in the next few months. I'm still very much an
amateur,
and I'd like to try analyzing why the unit is not working and see if
I can
fix it. This assumes physical damage to the circuit board of some sort.
<...snip....>
The only way to be sure it is capacitor plague is to gut the unit
and look
at the PC board. If you look at the capacitors in it, and one or
two are
slightly bulged, or have black stuff that looks to be leaking from the
bottoms, the device is dead, and should be replaced, unless you are
the
hacky type and change out the cap's or harvest the good parts off
the corpse
of the old switch.
~Seann
The unit has a blown capacitor, bulged and brown matter around it.
Also there is
a white-ish powder under the PCB. It looks dirty. There is corrosion.
Not sure it's
worth fixing. It went on for well over a year working perfectly in a
well ventilated
room. The unit is for a server at my workplace, so they will replace it.
Many years ago, I used to make and fix network cards and switches at
some
company, so I'll give it a shot myself at fixing this one just for
kicks.
I very much appreciate your offer to fix this thing --even though
there was no
warranty implied. :-)
Now, I've got to get a more reliable unit to last longer.
~af
One of the more common mechanisms for failure of electrolytic
capacitors is too high an ambient temperature over a period of time.
Usually the temperature rating is on the cap. You say the room is
well-ventilated but that doesn't rule out too high an ambient
temperature in a room full of equipment, especially if it was sitting
on top of or in a rack full of other equipment. It's more likely to
have open rather than short circuited. An ESR (effective series
resistance) meter will tell.
If you're pretty sure the capacitor is what's ailing it and it's
through-hole rather than surface mounted, I would consider it well
worth fixing, or even trying if there's greater than a 10% success
probability. Many 8-port switches aren't worth fixing below that.
Nuts and Volts did a photo of the workshop of a highly skilled
electronics hobbyist who gets all his stuff from junk piles, then fixes
and reuses the items. That is my nature too. It must come from my
grandfather. When his sawmill needed a replacement engine, he got one
out of a junkyard, refurbished it, and set it to work. It ran
beautifully for years to his considerable profit. If you pay little and
sell dear, you can't help but profit.
Fix it, if possible.
Bob
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