In article .net,
DaveC wrote:

Today I ordered electrolytic caps. It was frustrating. I had planned to get
the best low-ESR replacements for all the caps in some switching power
supplies. I discovered how limited any one manufacturer's low-ESR catalog is.
Many of what I needed (none of which seem to me to be esoteric values) were
not available. A couple of times I had to leave a particular manufacturer's
catalog altogether to find a value.

How critically are you trying to match the values?

Please remember that 'lytics are manufactured and sold with a rather
wide tolerance range. For example, the Panasonic FM and FC series
have a +/- 20% tolerance specification, and the nominal values they
list (in the Digi-Key catalog at least) are around 20-30% apart... so
there's some amount of overlap between the values you'd expect to get.

Older caps were often sold with -20% +80% tolerance, which meant that
you could end up getting quite a lot more capacitance than you had
"paid for".

In most cases, these days, I'd just look at the space I have available
to fit the cap, and then pick the "equal or next largest capacitance,
equal or higher working voltage" to what the BOM calls for. Unless
there was a particular need for a specific value (e.g. for timing
purpose) I wouldn't sweat about things like "the BOM calls for a 220
uF, and all they have in that size is a 330 uF."

And, if there were timing issues involved, I don't think I'd be using
a 'lytic at all in that application!

Which brings me to my question. I was trying to get all Panasonic FM-series
(hi-temp, low-ESR) caps. I've heard good things about Panasonic's caps, but
being forced to another brand I has no idea of comparable quality. (This, at
Digi-Key and Mouser.)

I've heard good things about Nichicon, and have used them in some
repair/retrofit projects. Don't have anywhere near enough information
about long-term performance to be of help with your question, though.

Also, How important is the type of electrolyte? I've read that low-ESR caps
are frequently made with water-based electrolyte whereas non-water-based
formulae cannot give low ESR value.

For what it's worth, I've seen several of the PC-motherboard
manufacturers touting their use of solid-electrolyte capacitors for
the CPU VRM... and this is a high-current, high-ripple, low-ESR-
is-very-important application. One manufacturer was citing a "50,000
hour" lifetime figure on the motherboard carton (although I think this
assumes very good cooling of the board).

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
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