Tech Chat NEFF Induction T53T86N2 five zone Hob fault
Just had a look at mothers 3yr old hob that blew the main trip, the three induction plates on the left are now dead with an error flashing a backwards 9.
Anyway opening it up found left and right power boards, the right hand side has a lower rating for two induction plates and a much higher rated board on the left that powers the three bigger induction plates on the left that have a boost power option.
Testing the IGBT output pairs showed two had failed dead short, also the rectifier was shorted. IGBT is insulated gate bipolar transistor a mix of a mosfet and transistor. As well as the rectifier being shorted the PCB on the reverse side had what can only be described as a fusible area that is designed to blow away in three separate areas, this had made a right mess.
Few days later all parts were fitted and tested with no magic smoke but still the error remained, tested the four gate drivers and they all tested fine, so where next. After an hour of probing around it revealed that a single DPDT relay had fused in the energised position the contact released with very minimal intervention after which the whole hob was functional again.
What surprised me was all the driver pairs and rectifiers are fitted with torx screws and no thermal paste, also found none were flush to the heatsink leaving an minute air gap which is possibly why it failed. As part of the repair this was added on all twelve.
Well done. These boards were never intended to be repaired hence the fuse tracks. When I serviced these we were only allowed to change the whole board, supposedly a safety issue. We must have thrown away hundreds when all they needed was a few bits replacing.
Hopefully this crazy waste will stop soon with the push to "save the planet".