hand mixer repair

[kuzao]

hello,
recently my trusty braun hand mixer died. it started as sometimes not responding when switched on and now the mixer cant be witched on at all. when opened the pcb showed one dark charred spot before the thermistor. when plugged in and the switch turned on, this area throws sparks. furthermore the solder joint of the thermistor looks not good, could be a cold joint.
can somebody tell me if there is a way of fixing this (for example by covering the charred area with epoxy)?

thank you for reading
alex

 

[tunedwolf]

Make sure that the track with the burn spot in it is not broken, check it for continuity. Clean up and resolder all the joints that look poor.
It's pretty unusual to have arcing in the centre of a track unless it's broken. The only time I have seen this is when there are high voltage tracks on both sides of the board and the epoxy on the board itself is breaking down. Make sure there is not a component on the other side of the board burning through.
If the problem is high voltage tracks on both sides burning through towards each other, then cut the tracks on both sides and solder wires across them instead, just make sure both tracks are isolated from each other. If it is a broken track, a good scrape back to bare copper on the track either side of the break and a solder bridge across the break will suffice. If it is a component, well you will need to identify it and replace it. Cleaning up the board around the burn can be achieved with a fibreglass pencil.

rgds

 

[kuzao]

thanks a lot for the advice
its actually a one sided pcb so it is at least unlikely that the board is burning trough.
the. i checked and the track is not broken. on the other side of the burn spot are a thermistor and a capacitor. both look and smell undamaged. the thermistor gives the expected resistance when checked and the capacitor also the expected capacitance.
tomorrow i will try and and bridge the whole track with a wire.
thanks again
alex

 

[kuzao]

Hi, the mixer is working again. I tried to cut the track but was quite thick copper. Then I bridged the whole damaged track with a wire while at the same time resoldering the one bad looking joint.
After reassembling and the making of one bread dough the mixer works well.
Regards and thanks for the help.
Alex