Surface Mount Components

[Phidom]

Further to my previous post about the AEG induction hob, I am now trying to repair one of the two power boards that drive the induction coils. A new board is about £300 so is not an option. Brian (Dented Porsche) kindly sent me some info. but it does not include a circuit diagram. Two of the IGBTs (insulated gate bipolar transistor) were short circuited and I’ve found I can get replacement devices from Farnell. There is a more tricky problem, however. I had quite a job unsoldering the IGBTs as the legs are soldered on both sides of the pcb. When one of them came out it’s leg must have been pressing on a nearby glass surface mount diode, which broke in half 😥 There are 2 such diodes very close to each IGBT. There are no numbers marked on them and I don’t know how to identify a suitable replacement. As it happens, I actually need 2 diodes as I discovered another one that is open circuit when checking the others with the meter. The good ones give a reading of about 0.73 volts. What worries me is that these diodes are labelled on the pcb as ZD1, ZD2 etc, whereas diodes elsewhere on the board are labelled D1, D2 etc. If the ones I need are zener diodes I would need to determine the zener voltage. I wondered if those amongst you who have changed surface mount components have any tips about identifying correct replacements?

[electrofix]

Re: Surface Mount Components

this is a bit of a tricky problem. as you rightly say these will be zenner diodes most of the time the voltage is printed on the component but if not i am not sure how to proceed on this route

as a thought and thinking on my feet the next thing i would try is this

remove the good zenner carefully

make a circuit up with a battery and a resistor to put a small current throught the zenner to push it to its avalanche point and read the voltage with a digital multimeter

i am of course assuming that both zenners are the same

hope this helps

Dave

[Phidom]

Re: Surface Mount Components

Thanks Dave,
I have emailed EGO in Germany who make the module. I did wonder about trying to measure voltages on the good board (there are individual boards for the 2 left and 2 right hand rings) but it would not be easy to operate the hob with it dismantled because of the touch controls. The diagnostics may not allow the hob to run with one module disconnected anyway.

[Author]

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