Philips NOS axial caps - it's dead, Jim.

[Haenk]

Just checked my unused NOS Philips axial electrolytic caps (47uF 25V). Due to the high number (>100) of caps, this probably gives some realistic hints about the failure rate.
25% checked out good (capacity and D)
25% checked out "pretty much in specs" (20% lower capacity, D acceptable)
50% checked out faulty (capacity mostly below 30uF, D 2-4 times higher)

So combining these values with thermal and electrical stress when actually being in use for years, one should consider every single one being dead and in need of a replacement.

And a warning: There are a couple of sellers on ebay(de), selling the same caps most likely from the same original source. I doubt they have tested them, so better buy new ones instead.
(I'll dump mine as well, the likelyhood of failure is just too high and not worth the trouble...)

[TimFox]

Do you have the date codes or other data on their age?

[cvanc]

Got a picture?  Would these be the ones with a translucent spiral wrap that say MADE IN HOLLAND on them?  I've had bad luck with those over the years, especially in anything that runs warm.

[exe]

What would be a reason to buy such an elcap off ebay? Why not buy a new one, they are not horribly expensive.

[Zero999]

Does reforming them work? Try connecting them to 25V, via a 1k resistor and leaving them for half an hour or so.
Did you measure the ESR?

I think they're probably fake. Please post some pictures of them.

[wraper]

Does reforming them work? Try connecting them to 25V, via a 1k resistor and leaving them for half an hour or so.

Reforming won't help against capacitance drop. Capacitance actually rises when oxide layer becomes thinner with time.

[SaabFAN]

20% lower capacitance would be within spec, I think. When ordering capacitors now the datasheets often list +/- 20 to 35% deviation from the stated capacity to be ok.


ESR of these caps should be around 3 to 5 Ohms btw.

[edpalmer42]

Does reforming them work? Try connecting them to 25V, via a 1k resistor and leaving them for half an hour or so.

Reforming won't help against capacitance drop. Capacitance actually rises when oxide layer becomes thinner with time.

It would still be worthwhile to try reforming them.  I wouldn't be surprised to find that some meters give a weird reading on a capacitor that needed reforming.

Ed

[Haenk]

I'm pretty sure those are not fake. They came on old paper roll.

Unsure how to date them, printing is as follows:

47u T
25V
PHILIPS
030 K0
D7

According to http://wiki.ece.rose-hulman.edu/herniter/images/8/8c/Electrolytic_Cap_Info.pdf this translates to July 1993. The "T" translates to -10% tolerance; however I selected the semi-good ones by -20%, so the numbers of failed parts is even higher.

I'm not going to bother with refreshing them (probably), I just consider them junk. If I really don't know what to do in the next days, I might reconsider…