>From: "Brian Chase" <vaxzilla_at_jarai.org>
>
>Someone passed this along to me today. It's a current news item, but I
>though it at least tangentially relevant to classiccmp folks. You'll
>get a bang out of this one--quite literally:
>
>-> In September 2002, reports started to surface in the United States
>-> among brand name computer manufacturers that there were problems
>-> with low-ESR aluminum capacitors produced in Taiwan. Apparently, a
>-> poor-quality, water-based electrolyte had been supplied to multiple
>-> manufacturers of low-ESR aluminum electrolytic capacitors in
>-> Taiwan. Our intelligence sources in Taiwan later confirmed that as
>-> many as eleven manufacturers of low-ESR aluminum capacitors in
>-> Taiwan might have been exposed to the poor electrolyte. The
>-> electrolyte, which is a locally produced knock-off of the Japanese
>-> P-50 type water-based system, was produced without the proper
>-> additives required to stave off excess hydrogen gassing. Consequently,
>-> aluminum capacitors produced with the P-50 knock-off tend to fail
>-> catastrophically, by blowing open the rubber seal and leaking liquid
>-> electrolyte on the printed circuit board. These failures reportedly
>-> occur at half the rated lifetime of the components.
>
>http://www.ttiinc.com/MarketEye/zogbi_on_passives_20021014.asp
>
>ObClassicCmp: What are the expected lifespans of various capacitor
>types? I don't have any truly ancient systems, but some of them are
>coming up on the 20 yr mark. When should I look into replacing the
>old caps?
>
>-brian.
>
>
Hi Brian
Not counting defective caps, they can last a long time.
I have an old radio that the electrolytics are still in reasonable
condition and the radio was made in the 50's. I have others
that are only 20 years old and have failed. Switchers put a
higher load on the filter capacitors because of their instantaneous
and rapid demands. These are the most likely applications for
low ESR's. One should check the burst seal and make sure it hasn't
already blown or is bulging.
Electrolytics that have been sitting for several years should
be brought up slowly to reform the surfaces. The best way to do
this is to disconnect and put on a power supply with a high value
current limiting resistor. Many large computer grade capacitors
may have normal leakage in the ma range so choose the resistor
accordingly. Small capacitors in the tens of uF should have
microampere leakage.
Dwight
Received on Mon Nov 04 2002 - 19:47:00 GMT