My brother reports his RangeMaster has dead hobs and dead oven. The problem is quickly narrowed down to the induction hobs with some testing done. Three years ago, the same fault was reported and repaired for about £500. But it has happened again. And now the quote for repair is £800. With a one-year guarantee. A good money maker! The unit cost £3,000 new about 10 years ago. You might expect it to last longer.
Error code E6 is present and a dead fuse is observed. My brother tried changing fuse and it popped immediately (as to be expected) so he asked for help. He's a software engineer/manager by trade so I'll forgive him for thinking it would be as simple as a fuse

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Looks like one hob channel has a dead short. UK model runs both on the same phase, but European models look like they run off the two phases independently (half the hobs on one phase, the other half on the other.) Unfortunately, just running with the dead fuse is no good. Hob controller notices a dead phase and does not run at all. You would think a fail over mode where just the bad hobs are locked out would be okay for the short term. The unit has five hobs in total with the fifth being driven by another controller, and that too is locked out. The oven can be made to work by moving a connector over from the hobs, but *without disassembly* the oven will not function as the system locks out the oven and hobs with any fault present. Ridiculously bad design, very anti-consumer!
Anyway: a closer look reveals the bridge rectifier is shorted on all terminals, and there are two IGBTs bad. Removing the bad IGBTs shows the bridge rectifier has at least two shorted diodes. There is no DC bus short any more. Looking closely at the design it appears that all channels are independent and the PIC microcontroller merely controls the drive signals and monitors the current through the hobs. The PIC also looks at the phase of the AC waveform via an optocoupler. I cannot see any obvious monitoring logic beyond the hobs so I expect if the bad IGBTs were removed and the bad bridge rectifier replaced the unit would function OK but with one channel non-functional. It is possible that the system does a power on self test though so I can't guarantee that.
Testing the spot where the IGBT lived from gate to source reveals that there is 270 ohms to source there. That is not good. There is a gate pull down resistor but it is 15 kohms. So there must be something else dead. And indeed, I found the datasheet for the half-bridge controller (FAN7383) and it has a 10 ohm short between the Vb and Vs pins. So when the full might of the 32A single phase domestic cooker circuit went through that IGBT, it also took out the driver chip.
I cannot find any other shorts so I am hoping replacing the two IGBTs plus one bridge rectifier and one driver IC (plus of course the fuse) will bring the hobs back to life. If anyone has any experience with this, please chip in your thoughts! And I hope my brother will be able to use his cooker once more.
E.G.O. driver board 75.96475.316 / 75.475.316 / PCB 960.260-05