KZG Caps blown on a N.O.S item? (Can it happen?) - Page 1
Forum section: electronics / repair

author: Stonent
author_rank: Super Contributor
timestamp: May 20, 2017, 04:54:05 pm
content: I picked up a Juniper WXC-250 network device on ebay for $20. Apparently there are a large supply of them out there New Old Stock never opened. Mine was sold as Open Box, Never used. It was in the original packaging, sealed with tape in the original bag. All the accessories were in the box in the original bags as well as warranty card. The power supply had a sticker firmly over the socket warning to set the network switches on the back prior to first power on. The warranty void sticker was very firmly stuck on. (This is a 10 year old device).For the record I never really intended to use it for its original purpose, my interest stemmed from this Peter Brockie video :that it had a full PC motherboard inside and I wanted to use it as a PFSense router.Anyway after opening it, all the 6.3v 3300uF Nippon Chemicon caps were crusted over. The inside of the case directly over the caps had rust marks and the copper heatsink had a crusty black mark next to the caps. It looks pretty much like Peter's video above.I inspected the CF card and the hard drive. The CF card has all the files the same date in 2007, and the hard drive has no partitions or signs of data on it, so unless this guy spent an inordinate amount of time to make sure this thing appeared new and really lost his shirt on $20 for a 10-15KG item with free FedEx shipping it has never been used.I'm not really all that upset because the 1U case and power supply was worth the $20 and I have another board I can install. I'm more curious if anyone has seen bad caps on a old device that has never been used. (And I did test it, the device is dead as a door nail. I can short the power good signal on the PSU and it does spin up, but no brain activity)So... possible? And I will probably try to fix the board anyway, does anyone have a recommended part that's cheap that would be a suitable replacement for the original KZG caps. (105c rated)

author: BravoV
author_rank: Super Contributor
timestamp: May 20, 2017, 05:11:27 pm
content: That cap is standing right to that big heatsink, not sure if it was exposed to heat constantly ? As these cap are vulnerable to heat exposure, even they're branded.As KZG is 105C rated, suggesting to use 125C rated series like GXF or GXE or GXL or even GPD series that rated @135C.

author: wraper
author_rank: Unknown
timestamp: May 20, 2017, 05:13:45 pm
content: KZG series were affected by capacitor plague. So I wouldn't be surprised if they would bulge while just staying on the shelve. This certainly had happened with some other capacitors.

author: Stonent
author_rank: Super Contributor
timestamp: May 20, 2017, 05:17:08 pm
content: Quote from: BravoV on May 20, 2017, 05:11:27 pmYeah, but in this case, no evidence the device had ever been powered up after being sold.

author: Cyberdragon
author_rank: Super Contributor
timestamp: May 20, 2017, 06:31:50 pm
content: Caps do have a shelf life and can expire. Usually they just don't work or explode when used. It's odd that they burst simply from getting old.

author: Rasz
author_rank: Super Contributor
timestamp: May 21, 2017, 08:47:29 am
content: Pentium 4 celeron, it was useless no matter the capacitorsalmost all motherboards from the P4 era died due to capacitors, interesting to learn those caps died even non used.

author: retiredcaps
author_rank: Super Contributor
timestamp: May 21, 2017, 12:29:17 pm
content: Over at badcaps.net there are numerous examples of KGZ that have never been used go bad with domed tops and oozing. KZG is "known" to fail even without external signs of distress.

author: daveyk
author_rank: Frequent Contributor
timestamp: May 21, 2017, 12:34:11 pm
content: Quote from: wraper on May 20, 2017, 05:13:45 pmReally?! I've never heard of that. I'm happy that my company used 90% tantalum instead of electrolytic. I think tantalum caps are much better and work the same in decoupling situations.Sent from my iPhone using Tapatalk

author: SeanB
author_rank: Super Contributor
timestamp: May 21, 2017, 03:34:18 pm
content: Even tantalum ones fail, about the only ones with no lifetime limit are the glass frit sealed solid wet tantalum units, though they also have a nasty failure mode of going bang. As they are kind of expensive ( the ones I used were listed as costing $1200 each, in bulk, when I was ordering them in 1990) I doubt they would be used on anything with less than 6 figures in the cost. There are cheaper ones that use a rubber seal, but those buggers have the same life as an aluminium electrolytic ( we changed the failed ones with regular aluminium electrolytics, because you could not get them easily from Vishay) but have a nasty price premium, but the 125C 10k hour rating was nicer than the 105C 10k hour rating of the replacements, but they were easy to replace as the stuff came in for calibration and checking.

author: Wester547
author_rank: Newbie
timestamp: June 01, 2017, 08:42:14 pm
content: Both KZG and KZJ are the blacksheep of NCC/UCC (or were, rather - both series were discontinued years ago). Two exceptionally bad series from an otherwise good catalog of capacitors. It's commonplace for both series to produce an excess of hydrogen gas with their external leads still intact, without ever having been placed in a circuit before, just like Fuhjyyu, GSC/Sacon/Evercon, YEC, Rulycon, etc. What's interesting is that ALL the 3300µF 6.3V KZG died on their own but the 1500µF 16V KZG still "appear" okay.I'm not surprised that those CapXon LZ or GF? series capacitors died on their own accord either. CapXon is a truly awful brand. I would be interested to know how old they are, datecode wise, however. It isn't at all odd for liquid electrolytics to bulge of their own volition. You can only cut so many corners with respect to the electrolyte and other materials before it simply won't last, even in storage (unused). There are thousands of vastly complex electrochemical reactions taking place in an electrolytic capacitor. Good capacitors have the right oxidizers and neutralizers to keep these reactions to a minimum over the course of a very long time. Heat and stress will only act as the catalyst and accelerator of a volatile chemical reactant that will eventually occur anyway.

author: KE5FX
author_rank: Super Contributor
timestamp: June 01, 2017, 10:07:08 pm
content: Interesting, I was under the impression that the "capacitor plague" happened because an electrolyte formula was stolen from NCC and improperly reproduced by the thieves. Sounds like Nippon ChemiCon themselves had problems with that formula, unless this is a different plague epidemic altogether.

author: wraper
author_rank: Unknown
timestamp: June 01, 2017, 10:42:50 pm
content: Almost every manufacturer making LOW ESR caps was affected to some extent. Nichcon HM/HN, Chemi-con KZG/KZJ, Rubycon MCZ, lower tier manufacturers were affected much worse.

author: Wester547
author_rank: Newbie
timestamp: June 01, 2017, 11:25:04 pm
content: Quote from: KE5FX on June 01, 2017, 10:07:08 pmThat "stolen formula" urban myth held claim Rubycon was at the heart of the "plague" with the P-50/P-51 electrolytic formula for the ZA and ZL series being stolen and incorrectly copied. With that said, I've never seen any evidence to corroborate the idea that any such story is anything more than a rumor perpetrated by journalists who wanted to make the spate of low-impedance Taiwanese capacitor failures of 15+ years ago more than it actually was.Quote from: wraper on June 01, 2017, 10:42:50 pmNichicon did have a large bad batch of HM and HN (and possibly HZ, at least they seem to die quite often on old Xbox 360 Xenon motherboards) series capacitors, but I haven't seen a HM or HN with 2006 date codes or newer fail without a good cause so I think they took care of business. I've never seen a NOS Rubycon MCZ bulge or leak, so I don't think that series is truly bad, just too sensitive to heat for its own good, which seems to be a trait characteristic among ultra-low-Z wet electrolytics.Lower-tier manufactures seem to have failure prone general purpose capacitors as well, not only low impedance. Although I suppose they could be considered acceptable for very light applications such as bypassing/timing/coupling/decoupling, but those tiny cans seem to dry out much faster than their larger brethren and the subpar brands are no exception to that.