Breville B25B7DCS Microwave

[ppppenguin]

I have been wondering if the wrong size fuse was fitted by mistake, does the fuse rating of .8 amp sound correct for a 900 watt output microwave.
If the voltage is 1000 as mentioned above then it would need a slightly larger fuse.

Mike

I said "over 1000V" as I wasn't sure of the exact voltages used. I think it's nearer 2kV. Either way it will do a lot more than sting and you'll only be touching it once. Makes prewar TVs with mains EHT look positively safe. At least they can't deliver anything like an odd amp or 2 through an unsuspecting human.

Having had a 1200V DC mains derived belt (from a 'scope with a low current winding on the mains transformer) I can assure you that it hurt. I was lucky that the muscle contraction pulled me away but it was so violent that my arm felt sore for several days.

Since the fuses aren't expensive I reckon it's worth a go. An example: https://www.ebay.co.uk/itm/Microwave-Ove...0232558231
That vendor says they often go for no particular reason. My bold:

The fuse will fail if there is a fault in the high voltage circuit. Such a fault could be a short circuit magnetron or a short circuit high voltage rectifier. In our experience however this fuse commonly fails for no apparent reason. The fuse just gets stressed everytime the magnetron starts which eventually leads to the demise of the fuse.

[Crackle]

Thanks for the link

Mike

[boater sam]

800mA is normal.

The voltages is more than 2kV, the transformers normally provide around  1.7kV but the capacitor/diode is a doubler circuit.
Its touch once DEAD.

[boater sam]

? Sorry duplicated.

[ppppenguin]

Sam, thanks for the insight. I thought it looked like a voltage doubler, with the magnetron as the other diode. The real point is that you're just as dead, whether it's 1kV or 3kV. Even if you repair microwaves professionally you don't work on them while they're running with the covers off.

Some more expensive microwaves use an inverter rather than a hefty transformer. Besides saving weight, this allows the microwave output to be continuously controlled. A conventional oven pulses the magntron on and off to achieve lower powers. They still have to provide a lethal supply to the magnetron.

This guy has looked at how a microwave inverter works. Although he's aware of the dangers I'm really nor convinced about his measuement methods. Safely hooking up a 'scope to that board isn't trivial.
http://www.vk3hz.net/amps/Microwave_Oven...Supply.pdf

[Crackle]

Thanks Sam for confirming that, I will get one ordered. I have not heard back from Breville following my enquiry to them.

Mike

[ppppenguin]

If you're taking the Consumer Rights Act route then you need to get in touch with the retailer, not the manufacturer.

[Crackle]

I cant believe how unhelpful Breville are when I asked them to confirm the microwave HT fuse rating in this machine.

Response from breville.co.uk

Dear Mike,
Thank you for your contact.
Although the unit says it is Breville, please contact your retailer. We do not have any information on these microwaves, as we do not hold the licence any longer. They will be able to assist you further.
Your product is supported completely by the retailers own Customer Services and not ourselves. We do not have any information regarding the microwaves.
We apologise for the inconvenience caused.
Kind Regards,
Ann


I will just have to go ahead and order the .8 amp 5kv fuse.
Thanks for your help guys.
Mike

[ppppenguin]

They completely disown a product with their own name on it. What a great way to enhance your company's reputation. Not.

Though they are correct in referring you to the retailer. The customer's contract is with the retailer and it's the retailer's job to sort out any problems. The flip side of this is when a retailer tries to get out of their responsibility by referring you to the manufacturer. This is normally wrong but sometimes this can be appropriate, for example if the retailer acknowledges responsibility but says that the manufacturer can sort out the problem more quickly or simply.