14 Jan
2002
14 Jan
'02
9:39 a.m.
Louis Schulman wrote:
Old computer power supplies generally have big old electrolytic capacitors. When these
go bad, they can
cause real problems, and damage other components.
The literature indicates that many of these only have a working life of 2000 hrs., or a
shelf life of ten years.
Obviously, this will be exceeded in old computers.
So, should these be replaced if they exceed a certain age? For the screw terminal type,
is it necessary to
use "computer grade" capacitors, which can be fairly expensive? If one
can't find the right value in the right
size package, how much extra capacitance is acceptable? And any higher working voltage
rating is OK?
Enquiring minds want to know.
Louis
IMHO, it depends mostly on who made the electrolytics. I have large
"computer grade" electrolytics from the 60's, salvaged from Ampex VTR's
that are still 100%, and have never failed in over 30 years.
OTOH, the cheap electrolytics found in consumer grade electronics seem
to dry out and fail on a yeary or biannual basis. One of the worst
failure rates I've seen is the teeny tiny 160VDC electrolytics; I just
replace then no matter what and usually that cures the problems.
The best way to check those #$%#$%^# caps is to use an ESR meter. And
only then should yo buckshot them. And replace them with good grade
Spraggue or CDE if possible. I've had mixed to poor resutls with
Nichion, or other cheap Japanese caps sold by MCM Electronics.
Gary Hildebrand