8mm Forum: Sound amplifier filmosound 202 + GB Bell & Howell 631

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Topic: Sound amplifier filmosound 202 + GB Bell & Howell 631

Lucas Elzea
Junior
Posts: 3
From: Vienna Austria
Registered: May 2008

posted June 06, 2008 09:11 AM

Hello I am new to this forum and very happy to see that there are still film enthusiasts out there.
I would like to restore a damaged sound amplifier from a filmosound 202 projector. The first problem I have is the power supply which should be "110v ac or dc 10 amps", according to the sheild on the projector case. Since i am living in Austria I will need a step down transformer or do you think it is possible to exchange the input transformer to one that takes 230 volts? ( the transformer is not on the amplifier but attatched with a 11 pin cable ). On the back of the amplifier however it says "117 volts 50 -60 cycles .9 Amps", so I guess the 1000 watt bulb of the projector is eating up the other 9.1 Amps. I have a schematic of the amplifier but it is hard to read so I am not sure what the Primary, S1, S2, and S3 values should be.
The other projector I have is the British made Bell&Howell 631. This is strangely enough also 110 volts and the amplifier is COMPLETELY different in layout and design compared to the american made one. A strange beast indeed. If anyone has schematics from this one I would be very grateful. I hope someone can help me out with my vague questions, I am certainly no expert and I assume the first thing to do is to power them up and see if they work at all, or should I replace some parts before even attempting to power them up?
Thanks for your help
Lucas [Confused]

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Jan Bister
Darth 8mm

Posts: 2629
From: Ohio, USA
Registered: Jan 2005

posted June 06, 2008 05:25 PM

Wow, tough one.

I've recently been investigating step-down transformers myself as I'm preparing to move to Argentina from the USA, or in electrical terms, move from 110V/60Hz to 220V/50Hz. There are high-capacity stepdown transformers available which are suited for continuous operation, but in your case what might be worth trying is picking up a cheap travel converter which handles high capacities (there are models available for up to 50W or up to about 1600W), however it will NOT be able to work continuously and will simply burn out if you try to. But to test your projectors and see if they're working before you dive into replacing their transformers, this should be the perfect way to go. Good luck [Smile]

Oh, almost forgot: http://www.voltageconverters.com/

Edit: Doh, forgot another thing! Hi and welcome Lucas [Smile]

--------------------
Call me Phoenix. *dusts off the ashes*

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John Whittle
Jedi Master Film Handler

Posts: 791
From: Northridge, CA USA
Registered: Jun 2003

posted June 06, 2008 08:17 PM

Lucas,

The plate on the 202 is the total draw with the lamp, projector motor and amp.

You can get in and modify the wiring a bit and use a step down transformer for the motor, a new transformer for the amp (although it will probably be easier to use a step down for the amp and motor so you won't have to find a transformer with all the proper sub voltages of 6.3 volts and whatever the other several taps are for the amp and exciter lamp).

Then wire the lamp to take the 230 volt service and replace it with a local lamp that is 230 volts instead of the US version which is 110/117 volts. The lamp is your biggest amperage hog in this machine and thus you probably can run the motor and amp on a 300 watt stepdown transformer and then the lamp direct off the mains.

Make sure you've got a schematic for the 202 amp since there are a couple of capacitors in there that will probably be bad due to age and type of original constructions. These can be replaced with sealed caps like Sprague Orange Drops and they'll restore the amp to it's original condition. The amp is a bit tricky since there are a couple of high frequency ossciallator circuits to run the exciter lamp and a record bias for the mag head and erase current. You'll also want to wash (with proper electronic cleaner) all the wafer switch contacts.

John

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