Capacitor ID and replacement - Page 1
Forum section: electronics / repair

author: Dunk_c
author_rank: Contributor
timestamp: July 31, 2022, 04:23:43 am
content: HiCan somebody please confirm identity of this cap, is it a Kemet 0.022uf, 1000v, poly cap, 15mm leg spacing?I was replacing IGBTs in an induction stove and accidentally melted two on the board (I could shoot myself). Then while trying to desolder another two they got too hot and also fried.I think the only way to get them out is to destroy them from the top side to get at the legs. Any better suggestions please?Any tips to installng without damaging them again?Is this the correct part from RSC?

author: Dunk_c
author_rank: Contributor
timestamp: July 31, 2022, 06:11:30 pm
content: Anyone!!!

author: wraper
author_rank: Unknown
timestamp: July 31, 2022, 06:22:36 pm
content: Yes it's Kemet R76. There is no problem desoldering them. Just melt one joint, pull the capacitor out from that side a bit. Then do the same thing from other side. Do this 2-3 times from each side and it will be out. As of Damage, I don't think that replacement is really needed. You just melted an outer shell a bit, not even through. Capacitor itself is inside potted with epoxy which will not melt. So it's just a cosmetic damage.

author: Dunk_c
author_rank: Contributor
timestamp: July 31, 2022, 10:26:47 pm
content: ThanksDesoldering is an issues as there is a large area of copper under each leg and the lead free solder is also a problem - freezes very quickly. Managed to the get IGBTs out but it was not quick.Pretty sure the caps are cactus as when I measure them and compare to the identical board in the hob they have no capacitanceI found some on Digi-key and have cut them out so should be able to desolder now

author: TimFox
author_rank: Super Contributor
timestamp: July 31, 2022, 11:09:50 pm
content: Note that "MKP" denotes metallizedpolypropylene.Almost all plastics' names start with "poly", including the other popular film dielectric, polyester (aka MylarTM), or "MKT", which has much higher loss (lowerQ) than polypropylene.

author: Dunk_c
author_rank: Contributor
timestamp: August 01, 2022, 12:22:00 am
content: ThanksEventually got them out! New ones ordered.

author: wraper
author_rank: Unknown
timestamp: August 01, 2022, 06:33:39 am
content: You can preheat the board which will make the job easier, just do it fast before PCB cools down. For example with hair dryer if you have no better options.QuoteDunno how and with what you measure, measurement result can a lot depending on it when you do it in circuit. But it's impossible they lose capacitance this way. You could melt them deeper so plates become shorted but it's impossible they lose capacitance because of how they are constructed. Leads are connected all across the edges of a roll. So it's not possible to somehow disconnect them by damaging capacitor in the middle. Maybe there is some another fault on the board which affects the capacitance measurement. As you already desoldedred them, I suggest measuring capacitance again out of the circuit. Also As you can see on the picture, roll (capacitor inside) does not even come close to the edges you melted.

author: Dunk_c
author_rank: Contributor
timestamp: August 01, 2022, 09:52:03 am
content: Happy to accept that information and learn from it - thanks.I could not desolder the caps even after applying heat and fresh solder for quite a oong tome. The caps got way too hot to touch but like you say maybe not too hot to destroy the component.The hob has two identical power boards, one broke, one was functional so I have a good one to compare to the one I am working on. Comparative testing of the caps in circuit showed that that part of the circuit was behaving differently. Anyway when the new caps get installed I can look for other faults. Other people have fixed the hob just by replacing the IGBTs and bridge rectifier and that all went well.

author: Dunk_c
author_rank: Contributor
timestamp: August 01, 2022, 05:59:44 pm
content: Digikey F*($#@ me over and placed the caps on back order until March next year even though they were showing as available to ship!!!!Can anyone sell me 4? Otherwise it is $40 for $4 worth of goods from RSC

author: Dunk_c
author_rank: Contributor
timestamp: August 10, 2022, 07:20:43 am
content: Quick followup…. New caps installed along with replacement IGBTs and I installed a fuse to replace a blown fuseable track on the mains input. $40 of parts saved me $900 for a new power supply (thats assuming they are available) or $5000 to replace this 15 year old Miele induction stove.