8mm Forum: Bolex M8 lamp upgrade

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Posted by Rob Watson (Member # 382) on May 31, 2007, 08:00 AM:

I'd like to upgrade the big old incandescent A1/7 lamp in my Bolex M8 to something brighter, but I'm struggling to find an appropriate replacement. I would have thought that something like the 24v 250w A1/223 would be an improvement but at 8000 lumens the light output looks to be well down on the 12500 of the old A1/7. Any suggestions?

Posted by David Pannell (Member # 300) on May 31, 2007, 11:05 AM:

Hi Rob, and welcome to the Forum.

1. Does your Bolex have a voltage adjustment for running on 110-120 volts?

2. What is the maximum recommended lamp wattage?

If the answer to 1 is yes, and the max. lamp wattage is 750W, do as I have done with my Elmo E-80 and Ampro Futurist. Set the projector to 110/120 volts, put a 750-watt, 115-volt lamp in, and run the machine from a 1kVA transformer. I have written reams and reams about this on the Forum, and believe me, you won't credit the difference in brightness! [Big Grin]

You'll get about a 40% increase in light output.

Briefly, the reason you have to go for the lower voltage lamp, is because the filament in the 750w 115v lamp occupies the same area as the one you have, whereas a 750-watt, 230-volt lamp's filament covers a much larger area, and the condenser lens won't capture all the light. If anything, the picture will be duller than the lamp you already have.

I'm a bit biassed anyway, towards these older technology projectors, and I prefer to stay with the original basic design - but then that's just me. [Razz]

Let me know how you get on. Good luck.

Best regards,

Posted by Rob Watson (Member # 382) on May 31, 2007, 11:32 AM:

Thanks for your reply David.

The lamp and motor in the Bolex run at 110V. The only lamp listed for it is the 500watt A1/7 (CZX in the US). The voltage drop from 240v is achieved by a massive coiled resistor which gets spectacularly hot, red hot in fact. Running the entire projector from a 1000w 110v transformer would solve that problem but would be an expensive business (in terms of buying the transformer). Also, I'd have thought cooling would be marginal with a 750watt incandescent lamp in a lamphouse designed for 500w. Thats why I was looking at a low voltage halogen alternative.

Rob

Posted by David Pannell (Member # 300) on May 31, 2007, 03:22 PM:

Yes. OK!

The scheme was only viable if the projector could accept a 750-watt lamp. Back in those days, some projectors were supplied with a 500-watt lamp, but the nameplate often stated that a 750-watt lamp could be used if desired. Clearly this is not the case with your machine - a pity.

I would certainly not recommend fitting a higher wattage lamp than the lamphouse and cooling system were designed for; and with the series dropper resistor, it is definitely out of the question.

Guess it's back to the drawing board. I'll be interested to hear how things turn out.

The question regarding a suitable transformer would not be a problem, as I have access to many such devices - but it's academic now.

Good luck.

Best regards,

Posted by John Last (Member # 3414) on March 20, 2013, 04:37 PM:

I have converted my M8 to accept the 12volt 100watt A1/231 lamp. An old 12 volt transformer from a Eumig projector can be fitted in the base of the M8. I needed to remove the old lamp base and the condenser lenses. The lamp is now secured in position with a simple aluminium plate with a hole big enough for the lamp and 2 holes to secure the plate using long scrws. The light output is better than the the 5oowatt version and the machine runs cooler.

Posted by Pasquale DAlessio (Member # 2052) on March 20, 2013, 05:09 PM:

Well done John!

Plus the lamp is a lot less expensive. I have done some conversions on the old projectors. It's rewarding.

PatD

Posted by Michael Wright (Member # 1387) on March 24, 2013, 04:21 AM:

Hi Rob there is a guy on ebay selling an halogen version of the original lamp which he claims is much brighter. Mike

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