[abrugsch]

My personal experience with a modern microwave (they mostly seem to be the same design internally, coming from the same chassis with the same electronics just a different button panel) was that the internal light bulb blowing generated a surge (it was a mains voltage bulb) that wasn't fused so the next nearest thing in the mains circuit was a trace on the motherboard that vaporized.

There is no way of easily changing this bulb (inside the main casing with no access panel for the bulb) so for want of a single in-line fuse, the entire microwave was rendered scrap[0] by the lifetime of a light bulb.

[0] - Except for the fact that I care not for electrical safety "DO NOT OPEN" warnings of doom due to being actually competent with handling high voltage equipment and being able to do a board level repair on the burned out trace without touching the very large capacitors associated with the very high voltage side controlling the magnetron...