30 Sep
2002
30 Sep
'02
6:37 p.m.
Bob Shannon wrote:
Thanks for catching my typo Joe. The MTBF (mean time
between
failures) is greatly REDUCED by unsoldering chips, often very
dramatically so.
Hmm, I never even thought of this one before.
Yet another general argument for sockets. :)
I would think if you had an adjustable DC supply,
you could gradually ramp up the voltage on the unregulated
input and watch the output with a voltmeter. If it ever got
to 5.25 volts, you'd not want to ramp any higher and replace
the regulator.
That wouldn't help with re-forming caps though. Maybe
you'd start at the output of the regulator and work up from
a very low voltage? Or would undervoltage hurt some
components due to a mysterious process I'm not aware of?
-- Ross
Ever notice the soldering specifications for TTL devices, like 300
degrees C for not more than 10 seconds? This limitation is given for
the parts to meet their rated MTBF, not because 300 degrees C for 11
seconds will destroy the parts right away.
Resolder the parts, and you may be throwing away well over half their
service life. Clearly not a professional way to restore a machine.
For some repairs, we have no other option, but melting solder is a
last resort.
Joe wrote:
At 10:38 PM 9/28/02 -0400, you wrote:
If you think this does the least dammage, your
grossly in error. As
a test engineer, I can direct you to any number
of volumes that will show you the dramatic increase in MTBF
I think you mean dramatic DECREASE in MTBF. But I doubt many
people on this list even truely understand what MTBF is. I worked in
reliablility, logisitics and maintainablity so I'm prpobably one of
the few that would catch this.
Joe
for
resoldered parts. This is known, for-sure
dammage, not some risk of
dammage from a theoretical regulator failure.
Care to defend this position?