Cabin Slide Projector

[DonaldStott]

The Osram bulb has suffered a very traumatic event at some point as there is evidence of arcing and an actual hole in the metal base - see attached. There is some writing but difficult to see clearly?

A replacement may be hard to find and possibly expensive but does anyone know a source for a bulb?

[Radio Wrangler]

The bulb holder may well be damaged as well as contact springs de-tempered.

David

[DonaldStott]

Originally Posted by Radio Wrangler

The bulb holder may well be damaged as well as contact springs de-tempered.

Thanks David - some evidence of arcing in the bulb holder but no damage apparent or probable cause while the spring is still quite springy.

From the damaged bulb base I've managed to decipher 'A1/21 UE' if that means anything to anyone?

[Trifocaltrev]

Hi, You could try The Lamp Company, their range is pretty vast!

Regards
Trevor.
http://https://www.lampco.co.uk/coll...rojector-bulbs

[Techman]

Plenty on ebay (which is where I always look for this sort of thing), but take note of the different voltage ratings.

[DonaldStott]

Before I invest in an expensive projector bulb I’d like to try a cheap and cheerful ‘sacrificial bulb’ just to ensure that my repair work has resolved the arcing issues in the lamp base?

Can someone confirm that this is a B22 type - it is bayonet fixing with a single contact at the base?

[ex seismic]

What is the voltage and power rating?

[emeritus]

That would be a SCC base. The 240V 300W bulbs for my mid-1960's Wray Moth slide projector have this base.

I found that the optical centre of the filament of the bulb for the Wray was not only exactly the same as that of the physically larger (taller) bulbs of my Gnome projector for the larger 2 3/4" square slides but was also the same as that of some 12V 36W SCC car headlamp bulbs that I had picked up in a government surplus store. When I was a schoolboy, to save using the expensive and relatively short-lived mains bulbs when sorting my slides, I used to fit one of the car bulbs, powered from an old mains transformer that had two 6.3V secondaries. Connected in series they could deliver the 12V at 3A needed to power a car bulb, which provided adequate light for a small screen.

[DonaldStott]

The damaged bulb I removed was 240V 100W - can't find any online suppliers?

[vidjoman]

As far as I can see it's a B15s based lamp. Used to be a common base type many years ago. Not sure which projectors they fitted but remember selling this type when I worked in a photographic shop in the 60's. Also recall there were several versions with different voltage ratings, but all basically the same. You must check whether it runs straight off the mains or via a transformer.

[peterpixel]

Hi Donald,there's a A1/21 on ebay at the moment which seems to fit the specs already mentioned. I Googled the type number and that was the first item that came up and it's not at a frightening price either. Perhaps you can compare what you have with what's advertised which was A1/21 115v 100w scc b15s. Obviously you need to check the voltage at the base which differs from the one you removed. Peter.

[DonaldStott]

Slide projector bulb runs straight off the mains so 240V 100W

[duncanlowe]

Funnily enough, I have just come across (again) a lamp with the same cap. Was a spare for my Dad's cine projector, except it was completely wrong. A Mazda lamp for a projector that 'improves colour rendition'. But 12v 100W.

[seymour32]

Hi Donald, I believe its a CJW/CJT 220V 100W bulb ( BA15s base) . if that helps

[vidjoman]

If your mains is above 220 volts be aware that lamp above will have a very short life. It’ll also be available as a 240 volt version. Projector lamps are always overrun to get the brightness.

[Techman]

Originally Posted by vidjoman

Projector lamps are always overrun to get the brightness.

They certainly are! If you're going to give it much use then I would advise getting several, as you don't get many hours out of them - probably around 10 hours as an absolute maximum.

[emeritus]

The Atlas 300W 240V bulbs for my slide projector were said in their instruction leaflets to have a rated life of 25 hours. I used to start mine with a watty resistor briefly connected in series to reduce the switch-on surge and they used to last longer than that.

In the 1960's, the "Amateur Photographer" used to have a regular column written by a professional projectionist. He once mentioned that, since using a Variac to start his projectors, he had never had a bulb fail, and had only had to replace them when their envelopes had become so blackened internally that their light output had fallen to an unacceptable level.

[Nickthedentist]

My parents bought a cheapish "Boots" branded slide projector in the mid 1970s. It was drummed into me and my brother that the bulbs were fragile and expensive, and that it was imperative not to put the projector away until it had been run with the lamp off but the fan still on for a few minutes.

We stuck to mum's rule and it's still on its original bulb!

[Techman]

I seem to remember it being written in the manufacturers data for the lamps in my 16mm projector that the expected life was 10 hours. Certainly I had one blow in mine a few weeks back and it didn't seem that long since I last replaced it, but probably just about 10 hours worth. A 'soft-start' with a Variac on a simple slide projector would seem to be a good idea, but unfortunately not practical with a 'movie' projector. Switching them on and off all the time isn't likely to do the lamp any good.

[emeritus]

In my 8mm Eumig cine projector, a low wattage "threading" lamp bulb is connected in series with the main bulb when the control switch is in the OFF, FORWARD WIND and REWIND positions. It allows enough current to flow to make the main bulb glow a barely visible dark red, and a heat filter is inserted between the film and the lamp. In the projection mode, the heat filter lifts out of the way and the threading bulb is shorted out, applying full voltage to the projector bulb.