Induction Hob Power Board Repair - Page 1
Forum section: electronics / repair

author: Lion_Tamer
author_rank: Contributor
timestamp: May 26, 2016, 11:45:57 am
content: Hi AllI am trying to repair a couple of induction hob power boards, they are identical boards with identical faults, we believe that they were damaged by a power surge, it appears that all the components have survived except the 2 flyback diodes (D22 and D122), I have replaced these and now need some help/advice on selecting the right fuse to repair the fusible traces at the mains input (top left of the second picture)There are two different size traces:Trace 1, W=1.56mm, L=1.30mm, D=0.05mmTrace 2, W=2.36mm, L=0.45mm, D=0.05mmMy calculations (using online calculators) suggest that Trace 1 would be around 10.6A and Trace 2 13.8A though the sticker on the PCB states 3700W (c16.1A), what size fuses would you suggest?Thank youJem

author: Gyro
author_rank: Super Contributor
timestamp: May 26, 2016, 07:43:42 pm
content: This is the second thread I've read today on replacement of PCB fusible traces(https://www.eevblog.com/forum/repair/washing-machine-motor-control-unit-repair/)<Rant>Since when did manufacturers start thinking that fusible tracks were acceptable on high powered mains stuff (or any mains stuff come to that)? It seems like a recipe for copper plating the landscape!It's not many weeks since I saw the last complaint about the use of glass fuses... This seems to be a step way too far! I can't imagine that it would pass any sort of safety approval.</Rant>@Lion_Tamer, I'm not sure if these are stand-alone hobs designed to plug into a 13A socket or permanent ones on a 30A cooker circuit. I think you need to trace out what each trace is feeding. I would err on the side of caution and go for no more than a 13A BS1362, or at least a ceramic fuse in appropriate holder for the high current one and if the other is for the control side, something considerably smaller. You obviously need to be careful with implementation and not to leave a couple of fuses flapping in the breeze.

author: Lion_Tamer
author_rank: Contributor
timestamp: May 26, 2016, 09:09:36 pm
content: This is a 4 zone hob that is designed to be fed from its own 40A circuit breaker, it appears that each board has its own input filter circuit with one of the traces before it and one half way through.What is more annoying is that I have seen a different induction hob pcb from the same manufacturer that although it has fusible links it also has some unpopulated fuse holders crossing the same point so that you can just clip some new fuses in when they go. These ones have gone with one heck of a bang, I had quite a large area covered in carbon dust on the board which I have already cleaned up.Jem

author: Gyro
author_rank: Super Contributor
timestamp: May 26, 2016, 09:26:30 pm
content: Yes, I did notice that there was no topside space to insert substitute fuseholders, although the current is pretty high for a standard PCB fuseholder. I'd probably suggest discrete hard-wired feeds from a set of proper chassis mounted fuseholders, but I don't know how practical that would be.It looks as if component level repair wasn't high on the designer's list of priorities (never is these days).Chris

author: Lion_Tamer
author_rank: Contributor
timestamp: July 09, 2016, 04:20:46 pm
content: Well just to finish this one off, I found some schurter surface mount fuses and used those on the boards and all appears to be working happily.Jem

author: Gyro
author_rank: Super Contributor
timestamp: July 09, 2016, 05:28:27 pm
content: Looks like a good solid repair, rather safer than the manufacturer's implementation!Thanks for completing the story.