[time-nuts] Capacitor failures

Mark Spencer mspencer12345 at yahoo.ca
Fri Oct 22 09:35:27 EDT 2010


Good points.  The RHOS lead free solder issues also lead me to favour older gear.

On Fri Oct 22nd, 2010 9:25 AM EDT paul swed wrote:

>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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