E.G.O. induction hob driver repair (RangeMaster Proplus 110 Induction)

[tom66]

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 . 

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

[HarryDoPECC]

Personal experience, one partly helpful to you and other prob not so much

1. Is there an oven under?  Salty steam rises up into the induction electronics. That’s what killed my name brand cost-4-figures unit. If so, put baffle between and plenty of vents for the hob. Poor ventilation also tends to kill the electronics

2. Replace with an IKEA. From what I could discover there are only 2 or 3 factories in West that make induction hobs. IKEA costs mid 3 figs and comes from same supplier. Also, typically 5yr warranty vs 3 yrs for name brand at 6x the price.  That’s what I did after first fix lasted just 6 mo.  Cut yr losses.

Induction cooking is fantastic but induction cookers are a racket. 

[shakalnokturn]

Never faced having to repair one of these sad designs.
I have a little experience with the Fagor IX6 / IX7 models.

Before repairing it helps if you can understand why things broke in the first place. It isn't always easy or possible though...
I'd at minimum check the onboard power supplies look good, a poor  12V rail could mean messy gate drive.

Check the passive components around the gate drive IC, sometimes one of the diodes and low value resistors get taken out too.
I'll usually test everything all the way back from the gates to the microcontroller before replacing the IGBT's. Of course if the microcontroller got hit it's the end of the game...

[tom66]

Yes, I do suspect that the problem is the heat from the oven.  Though the oven was not in use when the failure occurred, there is limited shielding between the hob power electronics and the oven chamber.  This may lead to a shortening of the lifespan of the IGBTs over time.  It is also possible the fault occurred due to a pan with a non-flat bottom, perhaps this pushed the current a bit too high.  The controller is supposed to recognise this and turn the hobs off or ramp current down but if it is not fast enough, maybe it can miss it and harm the IGBTs.

I wasn't able to find exact IGBTs but found faster switching ones with similar Vce(on) and higher Vce/Ice rating, hoping this extends their lifespan.  I am going to suggest that the fans on the heatsink drivers be replaced and will pass the recommendation over for an IKEA induction unit, certainly better warranty is a positive.

[tom66]

I'm happy to report that repairing the 'dead' channel and therefore removing the short more or less fixed the unit. 

However, only 4/5 hobs work.  This is OK for now, but it would be good to know why the fifth does not work.  The non-working channel seems to permanently report a 'pan missing' error.  I would guess that the system measures the current through each channel and there is negligible current flowing due to a fault, which is causing the pan missing detection to fire.

Whilst repairing the unit, I found that TWO of the FAN7383 chips were bad.  The other chip had a short on the *low* side Vdd, however I could not identify any of the IGBTs as bad for that channel.  I replaced the chip during the repair as a precaution.  I suspect that this channel might be the one that doesn't work, but we were in a hurry to get the unit put back together so didn't get a chance to definitively identify it. 

I suppose it's possible that when the first bank of IGBTs failed, it put a lot of current onto the Vdd which damaged the other '7383 as well (whilst there was no short on the low side of the first '7383 with the bad IGBTs, the high side of that chip was indeed bad with a 10 ohm short.)  If that then damaged something like the digital isolator (it consists of two independent channels) then possibly the channel would never be turned on, meaning no current, and the microcontroller then determines the hob as being empty.

[Luckily1012]

Apologies in advance, to say I'm a rank novice is an understatement.

I have a similar issue with our Rangemaster, i.e., E6 error code, dead hobs and a blown fuse that pops immediately upon replacing. I think replacing IGBTs, a bridge rectifier and a driver IC is outside my current skillset especially considering my partner's mandated timeframe to get it fixed.

I'm thinking that the board in the third image (c05fb91d-904f-4fd4-bac1-e525546a8195.jpg) had all the bad components (IGBT, bridge rectifier, IC) that you replaced bar the fuse so if mine is the same (will check), replacing that whole board should fix the issue?

[tom66]

Replacing the whole board, if that is the one with the shorted devices on it, ought to fix the problem.  E6 code was mentioned on his hobs too.  However when my brother looked he could not find the board on its own, it was only available with the service tech doing the job for him.  Good luck.

Note that he had a 5 channel hob, which has 4 channels on one power board and then one auxillary board which drives the remaining hob. You must identify which of these is defective, as either board can cause the fault.  The fuse being blown is a good clue but you should also check the fuses on the auxillary board if one is present.