It's quite old, but a match to the double Neff Oven.
The time display goes blank after use. Otherwise it works normally for setting the operating time. Press stop, and it appears at 12.00. Can then be set and works normally, until the unit is used again.
Is there an internal battery that might have failed? It is never powered down.
I think the time display on my neff m/w blanks between certain hours, yours doesn't think it's 9pm when it's really 9am does it?
Mine doesn't. And since with this fault you have to reset the time after using it, unlikely. ;-)
On 05/11/2020 15:44, Dave Plowman (News) wrote: > It's quite old, but a match to the double Neff Oven. >
I wouldn't have thought so. Cookers are amongst the most annoying white goods that forget the time whenever there is a short powercut.
They then choose either:
to restart as if from midnight 1/1/1980 or flash 00:00 and refuse to do anything until you set the system clock.
We have one in each camp and of the same brand so it is possible to infer both that there has been a power cut and also how long ago.
Sounds like the DC power supply for the controller board is winking out for some reason. Like maybe when the microwave oven door opens and the light comes on ?
You'd need to dig up a sample schematic for a microwave, to see what "best practice/cheapest method" looks like and from there, figure out the fault modes possible.
My previous microwave needed a pretty decent DC voltage, since the display was vacuum fluorescent and the segment drive for that is like 18-27VDC or so. Other technologies will need different voltages. A LED based display could be neatly done off 5VDC. The voltage doesn't particularly matter, just find how they're making that voltage, and trace what could be shorting it out and causing it to current limit.
There's nothing adventurous about this one. A 5V design based off a 7805 (1 amp) regulator. The unregulated rail is used for relay drive, so that the relay current doesn't overtax the 7805. 7805 has thermal cutout, if it gets too hot, output is cut off. And naturally, they'll put the 7805 in there, with no heatsink on it. Because heatsinks cost money.
The relays around the edge, could be feeding interfaces on the microwave board, whatever that is. They'd likely want some isolation between the two circuits, to reduce the opportunities for HV leakage from the microwave section, blowing up the controller.
You'd be looking for a center tapped transformer wire set, three wires, feeding from some transformer to the controller board. And right after that should be some rectifiers to make pulsating DC. Which needs to be filtered by a cap. Check the cap for brown leakage. High voltage caps, the fabrication is pretty careful. Filter caps for 5V, any Chinese junk will do.
Paul
Yes I had that issue with a 12v regulator in a cassette deck. shove a heat sink on it and all was sweetness and light. Insufficient testing. However in this case I'm intrigued why would a time be needed to be blanked at any time of day? Is it made by weightwatchers, ie after 9pm you are not allowed to cook? grin
Brian
I wonder could this be a leaky electrolytic which is supposed to cover a bit of a pulse in the supply but no longer does? Brian
Ab alternative from bigClive
Getting them on the internet of things can't happen too soon for my liking.
I was rather pleased to find that my new latest toy (GoPro 9) sets the date and time either when you enable GPS or connect it to a smart phone.
Mine blew up destroyed the magnetron inside guarantee a few years back and I was surprised to see inside that the mother board had a wifi networking chipset on it. The service guy told me that in theory you could scan the QR code on a product and it sets the timer accordingly.
However, AFAIK this functionality has still not been fully implemented on any production models or enabled on existing ones. The hardware was physically present in the build but the firmware support was/is not.
GPS has become the time standard of choice these days.
Or just remove the clock functionality and leave them with timers; I mean honestly who has ever gone to work and set the oven to have their tea cooked ready for whatever time they expect to get home?
I suppose we should be grateful washing machines don't have clocks too.
Only time I've used the timer is for an enormous turkey Xmas day. Worked just fine.
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