[time-nuts] Capacitor failures

[paul swed]

I have picked up and repaired for my own use many pieces of HP and other
high end equipment and what you are running into is almost the first thing I
check. Though actually my first steps are a careful visual inspection then
measure the power supplies looking for shorts. (Most likely from caps)
HP5386 that nicad battery is a disaster. When they go, very common in what
we buy (I have 5 3586s at the moment) they spew gook onto the regulators.
Worse if powered up in that condition the stuff arcs across and burns
traces. Very tough to clean up and repair at that point.
Back to the general comments.
What I am seeing in more modern gear is its the tantalums that are nasty.
They blow up and cause a lot of damage to the surrounding area. I just
picked up a SRS FS700 loran receiver and 2 had gone south. I replaced with
more traditional electrolytics.
Slightly higher voltage and capacitance.

Lastly I am afraid even if newer gear shows up that we can afford. Between
smt devices and special chips and 4 plus layer non traceable boards repair
is extremely difficult. Just when you think you have it all going you find
out some software is missing.
Afraid I will be eternally locked to to the 70s-90s for equipment.
Regards
Paul.

On Fri, Oct 22, 2010 at 6:59 AM, Bob Camp <lists at rtty.us> wrote:

> Hi
>
> If the pass element in the regulator has the emitter towards the load you
> probably are fine fiddling with the cap. If the collector is towards the
> load - check it with a scope.
>
> Bob
>
>
> On Oct 22, 2010, at 5:31 AM, Hal Murray wrote:
>
> >
> >> However I plan on replacing all the axial types in all of my HP
> equipment,
> >> except for the tantalums, with new 105C, low ripple, high reliability
> types.
> >
> > How does today's "low ripple" compare with back when the gear was
> designed?
> >
> > Some regulators oscillate without enough ESR in the big filter caps.  I
> > wonder if that might turn into a problem with old gear.
> >
> >
> >
> > --
> > These are my opinions, not necessarily my employer's.  I hate spam.
> >
> >
> >
> >
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