Identifying a capacitor  - Page 1
Forum section: electronics / beginners

author: LaptopGTR
author_rank: Newbie
timestamp: November 04, 2019, 03:49:30 am
content: Hi All. Please see attached image. I’m trying to correctly identify this capacitor. And wondering where I can buy this part. It’s from furnace ignition circuit. Any help appreciated

author: wraper
author_rank: Unknown
timestamp: November 04, 2019, 03:58:23 am
content: 0.68uF 400V

author: LaptopGTR
author_rank: Newbie
timestamp: November 04, 2019, 04:03:21 am
content: Thank you for the reply. May i know what type of capacitor.(I know its a bi-polar cap) also where to buy them. can not find anywhere online.thank you in advance

author: wraper
author_rank: Unknown
timestamp: November 04, 2019, 04:07:32 am
content: Some sort of film capacitor. Most likely does not matter much which type of film capacitor you choose as replacement for this. But using polypropylene would be the safest as long as size fits, they are larger for the same ratings than most of other types.

author: floobydust
author_rank: Super Contributor
timestamp: November 04, 2019, 05:11:08 am
content: Measure the lead spacings, they come in standard sizes i.e. 15mm, 22.5mm, 27.5mm etc. you want what fits on your pc board. The same part usually comes enclosed in a plastic box.0.68uF 400V polypropylene, you could look at EPCOS B32653, Wima MKP1, Kemet R75 series parts.Just look at Mouser for film capacitors and sort by size/voltage.

author: LaptopGTR
author_rank: Newbie
timestamp: November 05, 2019, 11:13:42 pm
content: Thanks for your informative reply. Just wondering whats the difference with this capacitor and the normal cap with same spec. on this board they did used the coated caps as well as blue boxed caps. rather using same why they used this specific once.also wondering whether these caps(my one on the pic) obsolete and not available any more or hard to find stuff

author: mengfei
author_rank: Regular Contributor
timestamp: November 06, 2019, 01:48:26 am
content: if that's not available try different types, as long as the Voltage is the same or higher

author: floobydust
author_rank: Super Contributor
timestamp: November 06, 2019, 04:44:20 am
content: That original capacitor is hard to find because it is so cheap. Film capacitors without an epoxy dipped coating or box are just cheap, fragile and vulnerable to moisture. Likely why it failed.Even a low cost chinese part has epoxy dipped coating like CBB22, or box CBB23 for $0.25 as 684J/400.Very very rarely, that particular capacitor is used because it has reliability and failure rate data available. That is used in the furnace's safety approvals, as part of ensuring the failure rate is low. More so with the flame detection circuit as that is safety critical. An igniter not working is dangerous but not really - unless it (this cap) can also take out the flame detection circuit (if it has a single flame rod). So there is a chance this capacitor is special only for that reason.I would replace it with a polypropylene, high pulse-current part from a reputable manufacturer. Let us know the spacings or dimensions or a pic of the board and can suggest something.EPCOS/TDK B32652A4684J000LS=15mm dV/dt 300V/μsEPCOS/TDK B32653A4684K000LS=22.5mm dV/dt 180V/μsIf you are doing the repair cheap, stuff in a CBB22 684J/400V.

author: LaptopGTR
author_rank: Newbie
timestamp: November 21, 2019, 12:27:22 am
content: fist of all thank you for your detail reply. sorry for the delayed reply. I did measure the gap between pins and its 16mmcan you please let me know the best cap to fix this board.

author: LaptopGTR
author_rank: Newbie
timestamp: November 21, 2019, 10:09:01 pm
content: fist of all thank you for your detail reply. sorry for the delayed reply. I did measure the gap between pins and its 16mmcan you please let me know the best cap to fix this board.

author: thedoc298
author_rank: Contributor
timestamp: November 22, 2019, 05:31:02 pm
content: https://www.ebay.com/itm/QTY-2-NICHICON-68UF-400-VOLT-POLY-FILM-5-QXK2G684JTPTZH/143246588580?epid=10021372146&hash=item215a297aa4:g:T7cAAOSw9KVcXepu