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Author Topic: Definition of technical term
Brad Kimball
Phenomenal Film Handler

Posts: 1171
From: Highland Mills, NY USA
Registered: Jun 2003


 - posted July 13, 2019 09:33 AM      Profile for Brad Kimball   Email Brad Kimball   Send New Private Message       Edit/Delete Post 
What is a motor run capacitor and can it be repaired or replaced? My Chinon 7000 runs for a minute or two and then it acts like a mower running out of gas. It lags with a hiccup intermittently. Belt is good and it’s well lubricated. A picture would be very helpful. Thanks.

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Mike Spice
Master Film Handler

Posts: 421
From: none of your business
Registered: Jun 2017


 - posted July 13, 2019 09:40 AM      Profile for Mike Spice     Send New Private Message       Edit/Delete Post 
everything you need to know about start/run motor capacitors

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Steve Klare
Film Guy

Posts: 7016
From: Long Island, NY, USA
Registered: Jun 2003


 - posted July 13, 2019 12:46 PM      Profile for Steve Klare   Email Steve Klare   Send New Private Message       Edit/Delete Post 
They can't be repaired, but they can be replaced.

You worry about three things in order of importance.

1) Capacitance:
These are there to introduce a phase shift into a current. It's what makes the motor spin. The capacitance shout be dead on.

2) Voltage:
This is a rating so the cap doesn't blow up. Going higher is fine. Going lower? No!

3) Size
Ideally you should find a new one that mounts in the exact same way and place as the old one. Frankly if you can meet capacitance and voltage requirements, making a fairly neat kludge mounting it up seems fine.

You need to find the cap and get the capacitance, voltage and size from it. I'm thinking a pretty large cylinder with two fat wires soldered to it: pretty close to the motor.

If you can find the exact part, that's awesome, but a lot of these old parts are obsolete now. We're lucky these days, with all these ceiling fans we have there are a ton of motor run caps available, it's just a challenge finding a good replacement.

Then again, it doesn't have to be the cap. I'm finding on my ST-1200HD it's more and more likely the motor switches. If I work them before I apply power, it runs like a champ. In the long term this means I'll probably have to replace the switches, which I am not looking forward to!

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All I ask is a wide screen and a projector to light her by...

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Mike Spice
Master Film Handler

Posts: 421
From: none of your business
Registered: Jun 2017


 - posted July 14, 2019 05:07 AM      Profile for Mike Spice     Send New Private Message       Edit/Delete Post 
I would also add, if you are not familiar with the dangers of capacitors, they can hold a powerful charge for quite sometime.

Motor capacitors in any shape or form will certainly hold a charge big enough to frighten the heck out of you should you accidentally catch the terminals.

Before you investigate removing an old capacitor.....

There are guides on you tube how to discharge capacitors safely, but don't be tempted just to short to earth.

I built a lead with a large resistor in it for this purpose.
Croc clip one end, test point the other, and i can discharge a capacitor in seconds, safely.

If you have a test meter, put it across the capacitor to witness the charge they can hold onto, in some cases, for many weeks after a power off.

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Maurice Leakey
Film God

Posts: 5895
From: Bristol. United Kingdom
Registered: Oct 2007


 - posted July 14, 2019 05:56 AM      Profile for Maurice Leakey   Email Maurice Leakey   Send New Private Message       Edit/Delete Post 
It's really a starting capacitor which throws a charge to kick over the motor for it to start. Once started it does not do any other work.
I suggest the motor problem lies elsewhere.

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Maurice

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