Identifying caps? - Page 1
Forum section: electronics / repair

author: Zzzt
author_rank: Newbie
timestamp: December 26, 2015, 04:32:59 am
content: Hi,New guy here.I'm trying to repair a PetSafe Pet Containment System - W402-533/2.I see two capacitors on the board that apparently have blown, but the side of one of the caps (c14) with the values printed on it is completely gone.If I'm reading it correctly the smaller cap (c1) appears to be a .1uf 250v cap.With no documentation on the board, what I'm wondering is if there's any way to make a reasonable guess as to the value of c14 based on the relative size of the two devices.(Photos attached)Any ideas or suggestions greatly appreciated.

author: Brumby
author_rank: Unknown
timestamp: December 26, 2015, 05:36:05 am
content: Can you post a photo of the underside of the board?

author: Zzzt
author_rank: Newbie
timestamp: December 26, 2015, 12:21:43 pm
content: Sure,Full front & rear.

author: wraper
author_rank: Unknown
timestamp: December 26, 2015, 01:16:26 pm
content: my guesstimate is about 0.47uF, probably 0.33uF. My advise to use X2 or X1 safety rated capacitors instead.

author: station240
author_rank: Unknown
timestamp: December 26, 2015, 03:43:38 pm
content: C14 should be 0.22uF, as this is a common value for filter caps on the mains side of small PSUs.Only larger PC PSUs have 0.33 or 0.47.Again replace with proper X1 or X2 capacitors for safety and surge capability reasons.

author: wraper
author_rank: Unknown
timestamp: December 26, 2015, 03:46:48 pm
content: Quote from: station240 on December 26, 2015, 03:43:38 pmThere is no PSU, what I see, it is powered from some power brick and switching some load.

author: SeanB
author_rank: Super Contributor
timestamp: December 26, 2015, 04:08:47 pm
content: It is a tuned secondary, using the 2 capacitors as tank capacitors and using a switch to select them as either 0.1uF ,0.22uf or 0.3uf to resonate with the coil. Thus I would suggest replacing with 100n 250VAC class X for the smaller one and 220n 250VAC class X for the larger one.http://eu.mouser.com/ProductDetail/Kemet/R46KI3100DQM1K/?qs=sGAEpiMZZMv1cc3ydrPrF0%2fKYujtVgoK1J%252b9rTV7rCo%3dhttp://eu.mouser.com/ProductDetail/Kemet/R46KN322000M1M/?qs=sGAEpiMZZMv1cc3ydrPrF512ADDNLQZJt5jBHoPB%2fCI%3dSamples from Mouser that they have available, though they will be a little bigger but should fit.

author: Zzzt
author_rank: Newbie
timestamp: December 26, 2015, 11:50:11 pm
content: Thank you, one and all!!I'll give those a try and let you know how it all works out.Yes, the switch is to select for the size of area (length of boundary wire attached) to the pet fence. It's meant for the wire to be shallow buried, and the dog's collar is triggered when in proximity to the wire. Actually belongs to my daughter, and they just had it strung along the vinyl rail fence around the property line. I'm wondering if it may have caught some lightening, being exposed above ground.Also, I'm sorry to be so slow to respond, but my boss seems to think I need to show up on Saturdays sometimes.Again, thank you very much.

author: Zzzt
author_rank: Newbie
timestamp: January 01, 2016, 02:56:28 am
content: The order from Mauser arrived today.Quoting SeanB;'Samples from Mouser that they have available, though they will be a little bigger but should fit.'Yes, they are a <little BIGGER> (see attachment). Couldn't fit both on top of the board and still get the case around it, so we just added some wire to one of the leads on the .22uf one and mounted it on the back side of the board.Looks really ugly 'til the case is back on, but the unit seems to work just fine.Again, thank you very much!

author: SeanB
author_rank: Super Contributor
timestamp: January 01, 2016, 10:50:18 am
content: Quality capacitors have to be bigger, as they run the dielectric at a much lower stress by making it thicker, and are better sealed so moisture does not degrade them so fast. Metallisation layer though is the same thickness, so that self healing can occur correctly, though the class X capacitors are much better at doing this by design.

author: Zzzt
author_rank: Newbie
timestamp: January 01, 2016, 11:37:05 pm
content: Good information to know.Thanks again.