Philips NOS axial caps - it's dead, Jim. - Page 1
Forum section: electronics / repair

author: Haenk
author_rank: Super Contributor
timestamp: March 20, 2020, 09:18:59 am
content: 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...)

author: TimFox
author_rank: Super Contributor
timestamp: March 20, 2020, 01:25:59 pm
content: Do you have the date codes or other data on their age?

author: cvanc
author_rank: Frequent Contributor
timestamp: March 20, 2020, 02:04:39 pm
content: 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.

author: exe
author_rank: Unknown
timestamp: March 20, 2020, 02:11:36 pm
content: What would be a reason to buy such an elcap off ebay? Why not buy a new one, they are not horribly expensive.

author: Zero999
author_rank: Super Contributor
timestamp: March 20, 2020, 03:01:15 pm
content: 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.

author: wraper
author_rank: Unknown
timestamp: March 20, 2020, 03:17:49 pm
content: Quote from: Zero999 on March 20, 2020, 03:01:15 pmReforming won't help against capacitance drop. Capacitance actually rises when oxide layer becomes thinner with time.

author: SaabFAN
author_rank: Frequent Contributor
timestamp: March 20, 2020, 04:53:46 pm
content: 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.

author: edpalmer42
author_rank: Super Contributor
timestamp: March 20, 2020, 05:37:00 pm
content: Quote from: wraper on March 20, 2020, 03:17:49 pmIt 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

author: Haenk
author_rank: Super Contributor
timestamp: March 20, 2020, 06:13:46 pm
content: I'm pretty sure those are not fake. They came on old paper roll.Unsure how to date them, printing is as follows:47u T25VPHILIPS030 K0D7According tohttp://wiki.ece.rose-hulman.edu/herniter/images/8/8c/Electrolytic_Cap_Info.pdfthis 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…