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Kelly, Appliance Technician
Category: UK Appliance
Satisfied Customers: 22865
Experience:  Highly accurate diagnostician with over 30 years experience!
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I have a Neff slide and de oven (model B46C74NGB) which had

Customer Question

Hi, I have a Neff slide and hide oven (model B46C74NGB) which had a blown lamp up until a few days ago.
Upon replacing the lamp with an exact equivalent (240Vac, 40W, same temp rating 300degC, same size and shape) there was a popping sound and since then all the interior oven lights in the door and at the top of the cooking area no longer work. The oven otherwise functions perfectly fine, the display and all cooking modes / temp settings work, just no interior lighting.
Any ideas?
Kind regards,
Submitted: 1 year ago.
Category: UK Appliance
Customer: replied 1 year ago.
Have checked condition of all the wires and the control circuitry, all seems to be without damage or any burning.
Expert:  Kelly replied 1 year ago.

Hi, welcome to Just Answer. My name is ***** ***** I look forward to helping you! I suspect you may have a halogen lamp that you replaced with a non halogen that damaged the power supply. Do you see a part on yours that looks like number 6 in the attached picture?

Customer: replied 1 year ago.
Hi,Yes I have a lamp transformer that looks exactly as in the picture. I checked the potential difference from the primary / secondary terminals of that transformer vs ground last weekend, but cannot remember the results. I can check again on Thurs (17th Dec) evening and report back, if that helps?Kind regards,Dave
Expert:  Kelly replied 1 year ago.

If you installed a 240 VAC bulb, that transformer was damaged, it takes a halogen specialty bulb.

Customer: replied 1 year ago.
Thanks for quick feedback.I installed one of these lamps: the same power / voltage (I did check that the replacement voltage AC and power consumption was the same vs the existing blown bulb when I initially examined it) I guess it was not the right type.I'll try a replacement transformer and bulb from Neff and see how it goes.
Customer: replied 1 year ago.
Sorry, before I go down that road, can you confirm the bulb I replaced it with was definitely not the right type?I'll check the transformer again tomorrow evening and report back.
Expert:  Kelly replied 1 year ago.

Odd, your model shows the bulb below. Does yours not have that style bulb?


Customer: replied 1 year ago.
Ah I see which you're referring to. Those are installed as a pair in the slide and hide door. I haven't modified those, I've changed the main interior light in the centre of the oven compartment roof.Now I think about it some more, the voltage on the primary and secondary of the transformer was a zero reading when the light circuit was meant to be on, but I'd need to confirm that.
Expert:  Kelly replied 1 year ago.

If the main bulb in the center that you replaced has a base as the one you linked me to, the bulb is not a halogen. The transformer is likely faulty if neither the halogens come on. That would be verified by no power at the transformer. It will take some investigation to determine why it went out at the same time the bulb was replaced, that is a bit coincidental if the new bulb does not work now, either.

Customer: replied 1 year ago.
Hi,I took the oven out again this evening and did a bit more checking. There is no voltage at the primary or secondary of the transformer, but confirmed there is a small resistance between the two primary terminals, and also between the two secondary no open circuit readings suggests it's ok (but haven't connected a 240Vac supply to primary to confirm that).Upon tracing back the wiring, the primary of transformer is wired in parallel to the main top interior oven light, which is fed from this electrical controller IC board: (naturally quite an expensive part!) checking resistance / continuity of connections on the circuit board to the main oven light, I've found what looks to be a little flat fuse on the board that's burned out (open-circuit) when compared to an identical looking component nearby which has good electrical continuity (see photo I've attached). This fuse on the control board would, if working, provide connection to spade terminals that lead to both the transformer and the main interior oven light.
These two fuses can be found on front left side of the board when looking at photo via Neff web link above. The fuse might have burned out upon initially replacing the main top interior oven bulb, although I have no idea why.So in summary, it looks as though this electronics control board is broken, but only this small fuse appears to be open-circuit. Do you know if one of these little fuses can be obtained?
Expert:  Kelly replied 1 year ago.

Nice find! the fuse is replaceable. Are you able to see any numbers on it or the other one?