8mm Forum: Question about lamp replacement

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Posted by Clinton Hunt (Member # 2072) on January 13, 2015, 09:17 PM:

Hi all,
I have a hand-cranked projector that has a 50volt 25watt (not 50w as thought) lamp that has blown and looks really old too and would be a dull picture projected...I am putting an adapter in the lamp socket to insert a halogen lamp.....do I need to have the same specs for the new halogen ?
The projector transformer for the lamp has variable voltage settings via a sliding lever.
Cheers,Clinton.

[ January 18, 2015, 07:35 PM: Message edited by: Clinton Hunt ]

Posted by Dominique De Bast (Member # 3798) on January 14, 2015, 04:35 AM:

It is not really a precise answer to your question but Grahame Newnham in the UK sells replacement kits and has a picture and spécifications on his site. You may be interested in having a look : http://www.pathefilm.uk/lists/filmlista.htm

Posted by Martin Jones (Member # 1163) on January 14, 2015, 05:13 AM:

Clinton,
Does your projector have any labels giving Manufacturer and Model Number? And what voltage settings are marked on the "transformer"?
Pictures, perhaps?
Your "transformer" sounds as if it's a Rheostat type voltage dropper, very common on old hand turned machines: the above information will help with suggestions as to your options.
Martin

[ January 14, 2015, 10:08 AM: Message edited by: Martin Jones ]

Posted by Clinton Hunt (Member # 2072) on January 15, 2015, 03:24 PM:

Hi Martin and all,
The make is an ALEF with no model number shown on the projector.
The lamp that was in there is a 50volt 25watt.
The transformer has a slide setter with the voltage from 90v up to 250v (It has a transformer that allows it to run on New Zealand voltage of 240v))

The projector is in good condition and rather than do a whole lamp-house conversion etc I would like to use the bayonet adapter and simply put a halogen lamp in.
And do I have to go to a max of 25watts or can I go higher for more light?

Here are the pics - anymore needed then I will post them too.
Cheers,
Clinton [Smile]

Posted by Martin Jones (Member # 1163) on January 15, 2015, 04:11 PM:

As I suspected, the "transformer" is a "dropper resistor" specifically intended to be used with a 50 volt 25 watt lamp ONLY. It is deigned to work at a fixed current of 0.5 amps and cannot therefore be used with a low voltage halogen lamp, which would require much higher currents.
I will post again soon with some suggestions.
Martin

Posted by Clinton Hunt (Member # 2072) on January 15, 2015, 07:25 PM:

Thanks Martin...... [Smile]

I can still get the lamps on ebay in the UK all up about GBP10

IF it is the RIGHT size I think....

Posted by Martin Jones (Member # 1163) on January 16, 2015, 02:05 AM:

Clinton,
I think you would be wise in the first instance to try the bulbs you've found. Electrical spec is OK, just check that physical size is OK.Buy more than one in case of damage considering the distance!
Filament position could be an issue. If they are satisfactory for light your problem is solved. If not, post again and I'll try to give you other options after doing the calculations on your dropper.
Martin

Posted by Ken Finch (Member # 2768) on January 18, 2015, 12:11 PM:

Hi Clinton, From your pictures it would appear that the bulb illustrated to my mind is not a projector bulb as it does not appear to have the normal straight filament of a projector bulb, therefor the light is not concentrated on the projector aperture.
Your projector appears to be an Alef 171 circa 1935 or a later version Alef Bilcin 172 of 1937 which was sold in the U.K.as the "Illustra". This did not have the facility for showing notched title films of the earlier model. Before proceeding further I suggest you thread a film and hand crank it through without any lamp to check that the maltese cross intermittent is not badly worn as these were notorious for wear. In any case a machine this old will be electricaly lethal! We would not wish you to get "Fried.! You would be well advised to use the 12volt 10 or 20 watt halogen alternative using the small transformer as previously mentioned by Dominique or build your own from a D.I.Y. store. Best wishes Ken Finch.

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