Exploding bulbs

[Gary Holliday]

I have an Omega C760 which I'm using as an extra enlarger for flashing. It's not linked through a timer, but plugged in directly to the wall.

Switched it on and the bulb exploded...I had been using it all morning and don't know why this happened...would it have been the fuse?

 

[Tom Kershaw]

On the theme of 'is it plugged in', is the enlarger bulb mains voltage?

Did you manage to clean up the glass?

Tom

 

[srs5694]

If by "exploded" you mean it literally exploded into pieces, then my first guess would be that something was in contact with the bulb. Can't certain liquids do this when sprayed on hot bulbs? Perhaps something leaked or dripped onto the bulb...?

 

[Bob F.]

I have an Omega C760 which I'm using as an extra enlarger for flashing. It's not linked through a timer, but plugged in directly to the wall.

Switched it on and the bulb exploded...I had been using it all morning and don't know why this happened...would it have been the fuse?

Unusual. Of course when switched on the stresses on the filament are at their highest (which is why they usually blow then) but to explode (actually, implode, but the effect is the same so far be it for me to be pedantic... ) seems unusual. Perhaps in melting, a piece of the red-hot filament dropped onto the glass and that was enough to set if off? 'Tis a mystery.

Did the fuse blow at the same time? If so, it may have been the lamp blowing that blew the fuse (it may have melted in a way that put a short across the terminals) or possibly a short somewhere blew both (the lamp filament would be expected to blow first as it is less robust). A ring-main fuse in the consumer unit is usually 30A and the plug fuse 13A, which are rather a lot. Either way, it would be very unusual to blow both lamp filament and fuse at the same time.

A residual current device is inclined to trip over something as simple as a blown lamp as they are very sensitive but not a fuse (the previous owner of my house specified RCDs in the lighting circuits so every time a lamp blows it takes out the whole floor's lighting until I reset the breaker...).

Bob.

 

[Dave Miller]

I have an Omega C760 which I'm using as an extra enlarger for flashing. It's not linked through a timer, but plugged in directly to the wall.

Switched it on and the bulb exploded...I had been using it all morning and don't know why this happened...would it have been the fuse?

Light bulbs have an internal fuse that is supposed to stop that happening, which it usually does, but some manufacturers in distant parts save money by leaving that bit out.

 

[JBrunner]

Working with all sorts of bulbs for many years, I have seen pretty much all manner of burn outs. With small halogens, mostly, there is a small flash and then that's it. Once in a great while they go off like a fire cracker, I've seen that maybe three times in twenty five years of being constantly around lights.

It's usually a flaw in the bulb, or the bulb envelope has been touched. Its a good idea to wipe down a newly installed halogen with an alcohol wipe to remove finger grease or anything else that may cause a hot spot.

 

[Frank Szabo]

I have an Omega C760 which I'm using as an extra enlarger for flashing. It's not linked through a timer, but plugged in directly to the wall.

Switched it on and the bulb exploded...I had been using it all morning and don't know why this happened...would it have been the fuse?

By definition, an enlarger is a machine, therefore, all machines being in the same union, will never miss an opportunity to puzzle their human 'masters' with all manner of nonsense.

Just get a new bulb and clean it well before installing - give the enlarger the raspberries and truck on.

 

[haris]

Bulbs do explode from time to time. Incadescent and halogen. Nothing unusual.

 

[Martin Aislabie]

It’s a flaw in the filaments glass envelope

A surface defect at the microscopic level would be enough to act as a stress raiser which over time can cause a bulb to fail

It is unusual but not unheard of

If it’s a Halogen then the acid on you skin from sweat will attack the quart glass – which is why the box of a Halogen Bulbs it tells you not to touch the glass directly with you fingers

It can be pretty impressive when the go – far more exciting than the usual “Pop” of the filament

Martin

 

[GeorgesGiralt]

Hi !
If the bulb is an Halogen one, this is not uncommon at all.
The wire used in the bulb gets thinner at place (during the halogen process).
When it cuts (be it wear ot vibration or whatever...) it may depending on the bulb position fall on to the two wires getting the current to it. It makes a short circuit drawing as much current the supply can give and giving a tremendous amount of heat which generally end in a small to moderate burst... This is why a lot of makers install the bulb with the socket in the upright position. when the wire cuts, it falls at the bottom of the bulb. I've seen halogen bulbs lighting a shop blasting the light fixture into the robe displayed and setting fire to it... Light can be fun some times ! (the light appliance was a cheap Chinese one without protecting glass and without surge current protection so be carefull when you shop)

 

[Gary Holliday]

Yet another reason to boycott Chinese goods. The bulbs are standard tungsten manufactured in the USA (230v). I got the bulbs from a Canadian ebayer and were working fine for quite a while. I believe the oils from skin may have played a part as I had removed the bulb to adjust the condensers.

I'm just thankful I had the filter drawer closed or I would be wearing some eye patches! This enlarger loves exploding...when I first received the enlarger, the UK distributor failed to supply me with a UK spec bulb and plug....boom!

I'm hoping the condensers are not too damaged.

 

[2F/2F]

Aw, shucks. I got excited and opened this thread thinking it was about flashbulbs...

The glass must have had a small flaw that was not noticed when it was made or installed. Likely the bulb got a knock in shipping as well, or perhaps when it was installed. It would have stressed more and more every time the light went on, and finally gave in. Most likely the flaw was at the meeting point with the metal screw base, or inside of it.

In general, light bulbs that are momentarily operated lead shorter lives than those that are on for long continuous periods. Makes sense from a metallurgical standpoint, and I imagine the same basic theory would apply to glass as well. This might never have happened if it had not been an enlarger bulb, always being turned on and off.

Anyone read about this light bulb? http://www.centennialbulb.org/