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Help needed with identifying Arri 2C constant speed motor parts


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#1 Bruce McNaughton

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Posted 26 February 2006 - 03:11 AM

Hi all

I have here an Arri 2C constant speed motor which needs 3 replacement parts. I have contacted Arri Munich and was given the Germanic brush-off. "Do you realize that this equipment is 30 years old...?" I say 'do you realize that there are still hundreds of these cameras being used every day...' Arri tried to tell me that they no longer had a parts list nor a wiring diagram. I don't know why they are so unhelpful, after 30 years they should have given up the propriety secrecy...

Anyway I digress... The parts are (1) the transistor. I need to know the type so that I can find a new one or an equivalent. (2) the two resistors that are cemented into the top of the motor. The only people who will be able to assist me with these are those who have worked on the motors and dug these out of their heat absorbing cement. I need the value of these resistors.

I'll be very grateful if one of you can help

Regards

Bruce
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#2 Dickson Sorensen

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Posted 26 February 2006 - 10:47 AM

Hi all

I have here an Arri 2C constant speed motor which needs 3 replacement parts. I have contacted Arri Munich and was given the Germanic brush-off. "Do you realize that this equipment is 30 years old...?" I say 'do you realize that there are still hundreds of these cameras being used every day...' Arri tried to tell me that they no longer had a parts list nor a wiring diagram. I don't know why they are so unhelpful, after 30 years they should have given up the propriety secrecy...

Anyway I digress... The parts are (1) the transistor. I need to know the type so that I can find a new one or an equivalent. (2) the two resistors that are cemented into the top of the motor. The only people who will be able to assist me with these are those who have worked on the motors and dug these out of their heat absorbing cement. I need the value of these resistors.

I'll be very grateful if one of you can help

Regards

Bruce

Motor-handgrip(centrifugally controlled transistor motor)
I have an old repair manual that has a page with an exploded drawing and a parts list. I'll scan it and send it to your email on your website.
The transistor is only labeled as "transistor" with no specs.
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#3 Clive Tobin

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Posted 27 February 2006 - 07:46 PM

I have here an Arri 2C constant speed motor which needs 3 replacement parts....


The two resistors are 5 ohms each, probably 2 or 3 watt rating, but I think they are overloaded and rely on the cement for extra heat sinking as wishful thinking to hopefully avoid burnout.

The transistor is a PNP germanium type with an odd mounting. If you cross it to a 2N307's replacement type or perhaps one with a higher current rating, say 15 amps, this will be a TO-3 metal can type with roughly similar specs. The case is the Collector which is still grounded. On the other two leads the Emitter is the one that goes to the motor armature. I don't know if today's more popular PNP silicon transistors will work properly in the circuit, I haven't tried it.

Shameless plug: If you want a really accurate motor you should consider our TXM-21Ab crystal motor. There are only a few left. Cheers
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#4 Bruce McNaughton

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Posted 28 February 2006 - 12:08 AM

Hi Clive

Thank you so much for the information. I have tried to find a substitute for the 2N307 without any luck. I don't suppose you would have a book there with equivalents...?

Regards

Bruce
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#5 Clive Tobin

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Posted 28 February 2006 - 01:59 PM

I have tried to find a substitute for the 2N307 without any luck....


After reviewing my sketch of the wiring, I think a PNP silicon transistor would work, germanium is going to be expensive and very hard to find these days.

Maybe an ON Semi # 2N5883 would work? This is in a metal can and good for 25 amps, at about $4.

Also check the Zener diode across the armature. If this is open it will cause premature failure of the transistor. I don't have a record of the type number or voltage rating. If your ohmmeter shows low resistance one way and high the other (disconnected from the motor), it is probably still okay.

Edited by clivetobin, 28 February 2006 - 02:01 PM.

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#6 Bruce McNaughton

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Posted 28 February 2006 - 04:41 PM

Thanks Clive

Regards

Bruce
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