Mystery Lighting problem

I have lights at the top and bottom of the stairs.
They both come on at once via switches top and bottom in the usual 'common' arrangement'. This is how it's meant to be.
The bulb at the top on the landing appeared to have failed. I changed it, still no joy.
With the landing bulb in place, but not working, I found that the lower bulb would not go off, using either switch.
Also the bathroom bulb fitting seems to have failed.
Any ideas?
mark
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Check for a loose connection block screw in a ceiling rose or light switch, starting with the two that have failed, but could be elsewhere, as they are all looped through. Caution (apart from the obvious one): there will be lots of wires in the rose, note where they are all connected before disturbing anything -- taking a photo is a good idea.
If you do find a loose screw, it may be wise to check all your other roses, as a poor connection can cause the block to heat up and melt, or worse.
Chris
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If not you may have the upstairs lights fused separately to the downstairs and the bulb blowing as also blown the fuse
Tony
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Most places I've been have the upstairs and downstairs lights switched separately, with two switches in wire-or for the upstairs one. I'm wondering if that's how "it's meant to be", but something was done wrong that made it the way you say.

This bit makes me think (at least?) one of the switches must have jammed -- it can happen that the visible part of the switch toggles but nothing happens to the contacts; on odd occasions the contacts can weld closed, but that doesn't seem all that likely, it's more likely that the mechanical bistable part of the switch has failed. But I can't quite see how this would make neither switch turn it off if they're wired the usual way.

Hmm.
All is not as it seems?
--
Jón Fairbairn snipped-for-privacy@cl.cam.ac.uk
http://www.chaos.org.uk/~jf/Stuff-I-dont-want.html (updated 2008-04-26)
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