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Topic: Carbon arc volts/amps

Paul Cunningham
Expert Film Handler

Posts: 146
From: Melbourne, Australia
Registered: Jun 2000

posted 03-31-2001 07:35 AM

I am mucking around with a couple of Peerless magnarcs at the moment. Not having a multimeter I got a friend to come around with his clamp meter and see exactly what current I was drawing, the results confuse me, this is what I have;
7mm negative
8mm positive
250v 50Hz running into a transformer then a basic rectifier
Output current when running is 55 amps at 3 volts.
The 3 volts is what confuses me as I was expecting around 30-40 volts.

What do you think?

Thanks Paul

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Jerry Chase
Phenomenal Film Handler

Posts: 1068
From: Margate, FL, USA
Registered: Nov 2000

posted 03-31-2001 08:35 AM

Check the meter setting? See if it registers a battery properly. My guess is the meter is being read at 1/10th value.

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Rick Long
Jedi Master Film Handler

Posts: 759
From: Toronto, Ontario, Canada
Registered: Nov 1999

posted 03-31-2001 01:06 PM

If memory serves, typical ratings for this trim should be around 70 amps at 25 - 30 VDC.
You did remember to dial the meter to D.C. volts, right?

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John Walsh
Film God

Posts: 2490
From: Connecticut, USA, Earth, Milky Way
Registered: Oct 1999

posted 03-31-2001 01:26 PM

I find that clamp on ampmeters for DC fairly inaccurate.

3 volts is not right, especially if the lamp is working normally. If so, I'd suspect the meter.

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Paul G. Thompson
The Weenie Man

Posts: 4718
From: Mount Vernon WA USA
Registered: Nov 2000

posted 03-31-2001 04:05 PM

I think your voltmeter has gone goofy.

Or, two other things:

If you are measuring the voltage using ground as a reference and you have only three volts, the lamphouse might be "floating".

If you are measuring using the negative lead as a reference, you should read the correct voltage. If not, your voltmeter is definately HS.

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Gordon McLeod
Film God

Posts: 9532
From: Toronto Ontario Canada
Registered: Jun 99

posted 03-31-2001 04:32 PM

70amps at 42 volts is the rateing on the 7mm negwith a 8mm positive

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Paul Cunningham
Expert Film Handler

Posts: 146
From: Melbourne, Australia
Registered: Jun 2000

posted 04-01-2001 09:52 AM

Thanks everyone,
The arc is burning fine.
I thought as Jerry did that it was only reading 1/10th value but it didn't indicate that was the case.
I will try it with another meter and see what I get.
Paul

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Michael Barry
Jedi Master Film Handler

Posts: 584
From: Sydney, NSW, Australia
Registered: Nov 1999

posted 04-02-2001 12:12 PM

Paul: I would LOVE to see a carbon arc lamphouse in operation - never seen one working before! (On the screen, yes - in the booth, no.)

If I ever get around to going to Melbourne I'd love to have a look...

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John Pytlak
Film God

Posts: 9987
From: Rochester, NY 14650-1922
Registered: Jan 2000

posted 04-02-2001 12:21 PM

Film-Tech has the 86-page National Projector Carbon Bulletins in the "Miscellaneous" listing of the "Manuals" section. The bulletins have a wealth of information on carbon arc lamps, with excellent background information on light measurement and optics.

------------------
John P. Pytlak, Senior Technical Specialist
Worldwide Technical Services, Entertainment Imaging
Eastman Kodak Company
Research Labs, Building 69, Room 7419
Rochester, New York, 14650-1922 USA
Tel: 716-477-5325 Cell: 716-781-4036 Fax: 716-722-7243
E-Mail: john.pytlak@kodak.com
Web site: http://www.kodak.com/go/motion

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Paul Cunningham
Expert Film Handler

Posts: 146
From: Melbourne, Australia
Registered: Jun 2000

posted 04-02-2001 08:43 PM

Michael

Yes, feel free to call in whenever you get a chance to come down, tha lamps are in my garage at the moment!

John, I have downloaded the National Carbon bulletins.

Paul

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Stefan Scholz
Expert Film Handler

Posts: 223
From: Schoenberg, Germany
Registered: Sep 1999

posted 04-05-2001 12:08 PM

Mycarbon lamp ran around 40 Volts with 7/8 MM.

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