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Old 29th April 2003, 11:58 AM   #11
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Gentlemen

I used to work on various systems that employed start/run capacitors. It was interesting to note that the same caps were sold to me over the counter for both start and run applications.

One of which is my air conditioning system in my home. It employs both run and start capacitors and both carry the same PN and are of the same size. This is not true of a lot of AC systems however.

I have also seen the better caps in the run position. With respect to leakage....I have seen some caps that never make it thru a years service. I would chalk this up to poor quality control instead of start caps being prone to leakage.

Joe
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Old 29th April 2003, 10:24 PM   #12
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Well clearly, if a run cap is high quality, then it'll suffice in place of a low quality cap of the same value.

Tim
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Old 29th April 2003, 10:27 PM   #13
dhaen is offline dhaen  Europe
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Quote:
Originally posted by Sch3mat1c
Well clearly, if a run cap is high quality, then it'll suffice in place of a low quality cap of the same value.

Tim
Huh! The idealism of youth.....

You're probably right!

Cheers,
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Old 29th April 2003, 11:23 PM   #14
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Hi,

Quote:
Well clearly, if a run cap is high quality, then it'll suffice in place of a low quality cap of the same value.
Don't expect it to work the other way 'rond though.

So, in conclusion; the motorrun cap should be the better choice...check out what it's made off and see if it suits the bill.

Cheers,
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Old 30th April 2003, 08:06 AM   #15
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Default Thanks for the help!

Thanks to all who answered. I did not appreciate the difference between start & run caps. Will make sure I use the run variety (properly bypassed, of course )
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Old 18th June 2004, 11:53 PM   #16
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I always thought an AC motor/run/start capacitor is useful for DC applications, ie B+.

However I am tared between people whom I should listen to, my father's brother says that capacitors which are marked as being 600vAC are specified for AC use only, IE, transformer-cap-motor, however what you /all/ say is that the /same/ AC capacitor can be utilised post-rectifier.

I asked the local techy: "What about post-inductor use?"
His reply was to change the subject and explain to me that anything AC specified and post-rectifier cannot be used because there is no capacitance whatsoever in an "AC" capacitor when peak/+ripple DC current is trying to be flattened out...

This is the same guy whom says that not all capacitors are AC capacitors which is true, but untrue in post-full-wave rectifier situations.

At least that is the jist of what I was told...

I just bought about 25 PIO/Motor Run capacitors off ebay very recently and paid for them, the total was $123 delivered within 4-6 weeks I sincerely hope I didn't make a foul up!!!.

To add to my confusion the original design of the amplifier calls for "500vAC" capacitors, is it merely a figure of voltage stated in the schematic to be later converted to DC for the actual purchase of correct "DC Operation" capacitors? or can I use "AC" capacitors?

I always thought a capacitors is a capacitor it smoothes a peak, ie holds a charge then lets it go in need, wtf is up? is these Motor Run capacitors non-polarised so they can hold charge of either peak, but will half their capacity during DC?

Is the capacitance values of these Motor Run/start caps specified for both active and neutral polarity swing and will halve during DC peak operation?

HELP!
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Old 19th June 2004, 12:25 AM   #17
G is offline G  United States
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Quote:
Originally posted by Layberinthius
I always thought an AC motor/run/start capacitor is useful for DC applications, ie B+.

However I am tared between people whom I should listen to, my father's brother says that capacitors which are marked as being 600vAC are specified for AC use only, IE, transformer-cap-motor, however what you /all/ say is that the /same/ AC capacitor can be utilised post-rectifier.

I asked the local techy: "What about post-inductor use?"
His reply was to change the subject and explain to me that anything AC specified and post-rectifier cannot be used because there is no capacitance whatsoever in an "AC" capacitor when peak/+ripple DC current is trying to be flattened out...

This is the same guy whom says that not all capacitors are AC capacitors which is true, but untrue in post-full-wave rectifier situations.

Relax. You did good. They will work well in your PSU. I have heard much more knowledgable people than I sing their praises as PSU caps. They can't all be wrong. I would however avoid mixing oil caps and electrolytics in your supply. Use all oil caps or film caps and you will have a very nice amp.

At least that is the jist of what I was told...

I just bought about 25 PIO/Motor Run capacitors off ebay very recently and paid for them, the total was $123 delivered within 4-6 weeks I sincerely hope I didn't make a foul up!!!.

To add to my confusion the original design of the amplifier calls for "500vAC" capacitors, is it merely a figure of voltage stated in the schematic to be later converted to DC for the actual purchase of correct "DC Operation" capacitors? or can I use "AC" capacitors?

I always thought a capacitors is a capacitor it smoothes a peak, ie holds a charge then lets it go in need, wtf is up? is these Motor Run capacitors non-polarised so they can hold charge of either peak, but will half their capacity during DC?

Is the capacitance values of these Motor Run/start caps specified for both active and neutral polarity swing and will halve during DC peak operation?

HELP!
Use the oil caps. They will work just fine. Ignore the convention loving infidels!
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Old 19th June 2004, 12:25 AM   #18
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I always thought this:

AC VOLTAGE:

The sum of the DC and Peak AC voltage applied to the capacitor should not exceed the rated DC voltage, nor should the RMS voltage exceed the Corona Start Voltage.

http://www.americancapacitor.com/Tech.htm

And I always knew this:

1.42 DCV per ACV

Working voltage (Wvdc, Wvac):

The maximum continuous voltage that should be applied to a capacitor. Rated voltages for DC and AC operation are usually not the same.

Quote:
Relax. You did good. They will work well in your PSU. I have heard much more knowledgable people than I sing their praises as PSU caps. They can't all be wrong. I would however avoid mixing oil caps and electrolytics in your supply. Use all oil caps or film caps and you will have a very nice amp.
Thanks G however I need proof to both proove to myself and to my amplifier, I'm not about to waste many hundreds of dollars to buy high-capacitance PIO caps for my 50watt/channel just so all of the AC ripple gets passed through... :\

They're 25 PIO capacitors rated at 17.5uF of 440vAC each... I did good? sure as hell I did!! at 130uF/channel filtering!! all PIO
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Old 19th June 2004, 12:33 AM   #19
316a is offline 316a  England
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Default PIO

Quote:
Originally posted by Layberinthius

They're 25 PIO capacitors rated at 17.5uF of 440vAC each... I did good? sure as hell I did!! at 130uF/channel filtering!! all PIO
Hope you have made the chassis large enough

cheers

316a
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Old 19th June 2004, 12:38 AM   #20
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Hope you have made the chassis large enough cheers 316a
I hope I can cut all the holes
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