I have quite an old Electrolux oven (model number EOB 51001), which has started making a loud vibration noise instantly as soon as it is turned on. This happens when turning it to any setting other than off, including grill or even just the light being turned on. So this rules out the main oven fan - it definitely isn't that. The sound seems to be coming from somewhere around the top of the oven, near the front.
Grateful for any suggestions on what might be causing this and how to rectify.