Checking bulbs with multi-meter

[KeithsTV]

From my experience of failed LED lamps there is usually a fuse or fusible resistor in series with the PSU bridge rectifier. If you're lucky this will blow when the lamp fails which is probably what has happened to your failed lamp where you are measuring an open circuit.

Keith

[Phil G4SPZ]

Well, in this case the input side of the bridge rectifier in the faulty CFL seems to be OK, as well as the reservoir capacitor, as evidenced by the initial 'kick' as the capacitor charges up through the diodes. The open-circuit must be beyond the capacitor.

[Electronpusher0]

Slightly off topic but I once had a water leak in a bathroom that made its way through to the ceiling below and a light fitting. The water somehow ran down the wires to the incandescent bulb.
The surprising thing was that the bulb was still lit, but with a few mm of water inside the bulb. I assume that the shock of the cold water on the hot bulb cracked the glass near the base and some water was sucked in by the (disappearing) vacuum.
Quite how the bulb remained lit without the filament burning out I do not know.
Obviously the mains was switched off at the board and a lot of drying ensued.

Peter

[The Philpott]

Peter, that's a sight that would send me running out of the bathroom!
The physics are interesting- a small amount of water expands to a huge amount of water vapour or steam, a cushion must have surrounded the filament preventing free oxygen from swamping it to destruction...but without being sufficiently electrically conductive to blow a fuse or fire the trip.

Now we are less reliant on incandescents we don't hear the 'bink' of death on a regular basis- funny the things you miss..

Dave

Dave

[Nickthedentist]

Originally Posted by Refugee

Back in the 1960s the local hardware shopkeeper used to have a live lamp holder on the counter to test all bulbs before sale.
Those days are long gone now though.

There was one of those, albeit with a momentary-action on/off switch, on the counter in the big department store in Wimbledon in the late 1990s, complete with large selection of different lampholders.

[Refugee]

If I remember rightly in the day the shopkeeper just shoved the bulb in and it lit up.

[emeritus]

Re #23, I have had that happen to a quartz GLS lamp used in an exterior bulkhead light, mounted with the transparent plastic cover facing down, that had let the rain in. The outer envelope had shattered, leaving the quartz intact. I drilled a drain hole in the cover to let the water out, stuck silicone sealant where I thought the leak was, and removed the broken glass. The lamp is still in use.

[Refugee]

I can remember seeing those outside lamps with the clear dome partly filled with water with the bulb dipping into it and still glowing away like nothing was wrong.

[ColinTheAmpMan1]

Originally Posted by Nickthedentist

There was one of those, albeit with a momentary-action on/off switch, on the counter in the big department store in Wimbledon in the late 1990s, complete with large selection of different lampholders.

Was that Ely's by any chance?
Colin.

[Nickthedentist]

Yes!