Bosch Combi Oven & Microwave HBC86P753B/01 Stops after 3 sec

[Thorpem]

Hi Folks,
I could really do with a bit of help in diagnosing a Bosch microwave issue
The model is: HBC86P753B/01 Combi Oven and Microwave.

https://i.pinimg.com/originals/5d/7b/5d … d23147.jpg

The problem only affects the microwave section:
The symptoms are as follows:
I power on and select microwave at any power level setting, adjust timer to 1 minute and press start, The light comes on fan runs for about 3 seconds and then display resets back to clock.
I am electronically qualified and aware of the high voltage risks, so dismantled to investigate yesterday. Magnetron shows no evidence of cracked magnets or distorted structure. Measures just under 1 ohm across heater with no leakage between either of the heater terminals and the case. If I run with the cover off, there are no sparks, unusual sounds or smells of burning.
The conventional oven responds correctly to door switch when opened.
This model uses an inverter PCB rather than the traditional capacitor and diode arrangement, so wondered if this module could be the cause. As the part is quite expensive, I thought it would be sensible to seek advice first. Are there any other items to check, or has anyone experience of this module failing?
https://www.partmaster.co.uk/control-un … HBC86P753B

Many Thanks
Regards
Mike

[electrofix]

Re: Bosch Combi Oven & Microwave HBC86P753B/01 Stops after 3

yes the modules can fail and do also so do the mags without showing leakage to earth

forget the silly price of the part you can get it for a third of that. unit are based on a Panasonic microwave

cannot say much on an open forum as we would not like the general public to start investigating 5000v

Dave

[Thorpem]

Re: Bosch Combi Oven & Microwave HBC86P753B/01 Stops after 3

Hi,
I just wanted to update you on the repair. I followed great advice provided here and traced back to the fuse which was under the rear panel.
Measured it and it had blown. I managed to get a replacement 7A slow blow from Maplin (Pack of 10 for about £3.75).

Carefully measured and checked all the door interlock switches and powered back up. Fuse didn’t blow and Microwave is still working perfectly with no additional parts required, so great outcome.

Best Regards

[sboffo]

Re: Bosch Combi Oven & Microwave HBC86P753B/01 Stops after 3

Hi Mike,

I realise this is some time after your initial post, but I stumbled it whilst searching for some help on exactly the same problem with my identical Bosch Combi.
On the of chance that you might still pick up on replies and seeing that you resolved the problem I wondered if you might answer a question.
I looked under the back cover of my unit and found a board that looks quite different to the inverter PCB you were initially contemplating to buy as a replacement part (from Partmaster).
Here’s a picture of the back….
https://www.dropbox.com/s/lcxfpt8z6i2e1wk/HBC86P753B-Back.jpg?dl=0

Am I looking in the wrong place, or perhaps my unit is using a different part to yours?

Any help would be much appreciated.

Thanks,
Steve

[electrofix]

Re: Bosch Combi Oven & Microwave HBC86P753B/01 Stops after 3

your unit is different and your invertor is inside the black box top left of your picture

but beware the sort of voltages inside that box are lethal

the only thing worth checking is there is a fuse on the main circuit board just for the microwave. find it and check if its blown

Dave

[vchook]

May I ask where exactly is the fuse as I have exactly the same problem. Thanks

[Author]

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