Smokey lamp capacitor! - Page 1
Forum section: electronics / general

author: InductorbackEMF
author_rank: Regular Contributor
timestamp: May 16, 2019, 07:25:15 pm
content: So i was fixing a remote thingy, when all of a sudden i hear a small hizz then a loud hizz,i look up and see my lamp buzzing and letting the magic smoke out,i rush it out the room thinking the inductor/ (or ballast) somehow died and set light,well when i opened it guess what i found...

author: InductorbackEMF
author_rank: Regular Contributor
timestamp: May 16, 2019, 07:26:10 pm
content: And yes there was a bunch of cracks in the case as always..Alex.

author: wraper
author_rank: Unknown
timestamp: May 16, 2019, 07:31:01 pm
content: Crappy Rifa firecracker yet again.

author: InductorbackEMF
author_rank: Regular Contributor
timestamp: May 16, 2019, 07:32:42 pm
content: I have had paper capacitors from 1940 last longer than this.Alex.

author: Gyro
author_rank: Super Contributor
timestamp: May 16, 2019, 08:13:25 pm
content: Wow, we're averaging about one a week at the moment!

author: Cyberdragon
author_rank: Super Contributor
timestamp: May 16, 2019, 08:57:13 pm
content: RIFA DETECTED!!!

author: james_s
author_rank: Super Contributor
timestamp: May 16, 2019, 11:26:45 pm
content: I still have only ever had one of these fail, and it was in a 25 year old at the time Apple IIe. Maybe they fail more often in 240V land?While less spectacular, I've had waaay more electrolytic caps fail, even good name brands.

author: wraper
author_rank: Unknown
timestamp: May 16, 2019, 11:30:34 pm
content: Quote from: james_s on May 16, 2019, 11:26:45 pmThey usually explode after equipment was not powered for some time. Of course they have higher chance exploding at higher voltage.

author: Zero999
author_rank: Super Contributor
timestamp: May 17, 2019, 09:27:05 am
content: If it's used as a snubber, rather than EMC, it will have a resistor, so will need to be replaced with one with a similar resistance, as well as capacitance or separate resistor and capacitor, wired in series.http://www.farnell.com/datasheets/300514.pdf

author: stj
author_rank: Super Contributor
timestamp: May 17, 2019, 07:41:04 pm
content: i know a shop with a whole drawer of NOS rifa's full of cracks, they cant bring themselves to bin them!i'll take a photo next time i'm there.

author: james_s
author_rank: Super Contributor
timestamp: May 18, 2019, 12:34:22 am
content: If they're old stock with cracks I'd obviously toss them. Likewise if I had a box full of old stock electrolytic capacitors that had high ESR or were leaking I'd toss those. I wouldn't hesitate to use a new RIFA or electrolytic capacitor in something though, it is well understood that these are consumable parts with finite lifespans.

author: GlennSprigg
author_rank: Super Contributor
timestamp: May 18, 2019, 12:03:23 pm
content: I may be shot down hereWhen you said a 'Lamp', you didn't explain/show if it was a 'Fluoro' ??As such, the Capacitor would have been present for 'Power-Factor-Correction",(due to the Ballast (Inductor) being present.)Many times, I've just cut the Capacitor out! from Fluoro units !!

author: Zero999
author_rank: Super Contributor
timestamp: May 18, 2019, 05:48:06 pm
content: It appears to be too small to be a power factor correction capacitor., but it's difficult to get a sense of scale from the photograph, so you could be right.Inductive ballasts can create a burst of radio frequency interference when starting up, so a capacitor is normally needed to suppress it. The starter quite often has a supressor capacitor built-in, but it wouldn't surprise me if some fittings also have an additional one, just in case.

author: Cyberdragon
author_rank: Super Contributor
timestamp: May 19, 2019, 05:51:21 am
content: Quote from: Zero999 on May 18, 2019, 05:48:06 pmFlouros generate RF all the time. Just take an AM radio into a room with flouros on. Not sure which is worse magnetic or electronic ballast.

author: Zero999
author_rank: Super Contributor
timestamp: May 19, 2019, 07:44:37 am
content: Quote from: Cyberdragon on May 19, 2019, 05:51:21 amElectronic ballasts yes, but magnetic ballasts don't radiate much over the AM radio region, other than a short burst at turn on and off.

author: InductorbackEMF
author_rank: Regular Contributor
timestamp: May 21, 2019, 10:19:47 am
content: Hi,it seems like the capacitor was only for EMC so no worry's i have replaced it with class x capacitor same value. (Not a rifa hehe)