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Topic: Upgrading projector bulbs ....
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David Pannell
Phenomenal Film Handler
Posts: 1072
From: Horsham, West Sussex, UK
Registered: Nov 2004
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posted February 21, 2008 11:19 AM
Many variables here, Osi.
Paul is right.
It's not for the feint-hearted among us and mods like this are really for the very technically minded. If you feel you're up to it, have a go, but I cannot stress strongly enough that such mods are fraught with far reaching implications. I have given a brief synopsis below of what some of the essential things are to look out for. If you feel the least bit nervous in tackling a project like this, and it IS a major project, - don't even think about it.
Firstly you have to be sure that the transformer in your projector is capable of supplying the extra current (in terms of amps) of a brighter lamp. The current is the all important factor and is arrived at by dividing the watts by the volts. Therefore a 12 volt, 100 watt lamp will need 8.3 amps to power it. A 12 volt, 125 watt lamp will need 10.4 amps to power it, and a 12 volt 150 watt lamp will need 12.5 amps to power it.
The transformer may or may not be able to supply this additional current, and if not, the lamp will be duller than the one you are currently using, because in an attempt to supply the extra current, the transformer voltage will reduce and it will and overheat. This is known as 'transformer regulation', and is the ratio of output voltage to current.
It is possible to find out if the transformer is capable of this, but you need a little electrical engineering 'know-how'. You will need to measure the voltage across the lamp terminals while the lamp is on. Do this first with the standard 100 watt lamp. The voltage should be pretty well exactly 12. If it is less than 12 volts, you need to REDUCE the mains voltage adjustment to the point where the lamp volts are 12 - with the lamp on. This is the lamp design and is most efficient when run at its rated voltage, or a tad higher, but no more than 12.5 volts. Conversely, if the lamp voltage is higher than this, then you need to INCREASE the mains voltage adjustment to the point where the lamp volts are 12.
Having done this, your 100 watt lamp is now running correctly. (You may find that it has been being underrun with less than 12 volts, and bringing the voltage up to 12 by the mains adjustment could well provide the additional illumination you are looking for).
You can now try a higher wattage lamp, still measuring the volts across the lamp terminals with the lamp on. If the voltage is more than half a volt LOWER than with the 100 watt lamp, forget it! Your transformer will become a molten mass of copper and iron in very short order.
You can experiment like this until you find the optimum lamp, but I wouldn't mind betting that the manufacturer has designed the system down to a price, and it is probably not capable of supplying any increase in load.
The next thing to consider is cooling. A higher wattage lamp will produce buckets more heat, so you will need to get rid of that additional heat somehow.
And as if all this isn't enough, the filament design and its position within the glass envelope of a higher wattage lamp could well be very different from the stock lamp, so all the optics could be out of alignment, with different focal lengths etc. etc.
However, if you are prepared to invest time and careful enthusiasm, consider a beefier transformer, a more powerful blower, and can align the optics correctly, - like others have done in the past, - you could be onto a winner.
Good luck!
--------------------
Dave.
Valves and celluloid - a great combination!
Early technology rules OK!
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