Sudden Reboots

[Doug Russell]

On Sat, 2 Oct 2004, Sean Farley wrote:

> I had sudden reboots over a period of two years.  Recently, they started
> happening more often.  It turned out that the capacitors had gone bad.
>
> Capacitors from about two to three years ago used a poor formula.  This
> site has information about it:  http://www.badcaps.net/.

Even the best quality new ones can wear out and cause these problems with
only the smallest of defects inside eventually making them unusable for
the type of circuitry they're used in.  (The current pulse demands on
these caps in switching regulators are absolutely rediculous).

I've got a whole little plastic bin full of them to replace ones on bad
boards.  When you order them, look very closely at the specifications,
especially at how much current they're rated to handle for a given value,
and get the ones with the highet current rating, even if you have to go
with a higher voltage (I often use 10v caps to replace 6.3v ones when
they'll fit, as the particular brands I've been using have significantly
higher current capability for the same uF value), and perhaps go with a
slightly higher uF value (really helps to understand the circuit, though.
Don't go TOO much higher than the original value).

> The interesting thing for me was that the capacitors did not show any
> signs for about two years.  They looked like they had flat tops without

Sure...  and these types of problems often show up only after being
powered off for some time, etc.  The OP said two of his boxes mysteriously
"fixed" themselves.  Just because they haven't failed for some time
doesn't mean there isn't still something flakey in there.

His problems REALLY sound to me like capacitor problems in the PSU or,
more likely, the voltage regulators on the motherboard.

Seen this type of problem many, many times.

Having an ESR tester is handy, also.....

Later......						<Doug>