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Old 14th February 2013, 06:01 PM   #1
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Default Advice Needed-Capacitor Value

I'm installing a new power switch on my Hafler DH-200 amp. I found a related thread here, and purchased the correct Mouser replacement switch based on the excellent information included in the thread.

It was also advised that a new capacitor of .01 uF, or higher be installed along with the new switch.

My question is if the ".01" value referred to is actually .001?
My local Radio Shack stocks this capacitor: .001uF 500V 2% H.Q.
The original cap marking appears as: 502M 500V, as per the Radio Shack employee (I could'nt read any of it).

As this is my first attempt making a repair electronic in nature, I want to be certain that I am using the correct capacitor.

Thanks for your help!
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Old 14th February 2013, 06:08 PM   #2
Mooly is online now Mooly  United Kingdom
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If the capacitor is across the switch (or anything mains related) then these days its essential to use caps called "Class X" type which are self healing.

0.01uf is 10nf and sounds about right for switch supression (I'm assuming thats what you are referring to).

502M will be 5000pf or 5 nf. So the 0.01uf sounds in the right value range for a mod or uprated part.
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Old 14th February 2013, 06:09 PM   #3
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Quote:
Originally Posted by itwashifi View Post
I'm installing a new power switch on my Hafler DH-200 amp. I found a related thread here, and purchased the correct Mouser replacement switch based on the excellent information included in the thread.

It was also advised that a new capacitor of .01 uF, or higher be installed along with the new switch.

My question is if the ".01" value referred to is actually .001?
My local Radio Shack stocks this capacitor: .001uF 500V 2% H.Q.
The original cap marking appears as: 502M 500V, as per the Radio Shack employee (I could'nt read any of it).

As this is my first attempt making a repair electronic in nature, I want to be certain that I am using the correct capacitor.

Thanks for your help!
Sorry, Just realized that this should have been entered in the amp. line.
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Old 14th February 2013, 06:11 PM   #4
Mooly is online now Mooly  United Kingdom
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Its done.
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Old 14th February 2013, 07:05 PM   #5
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Thank you Mooly. Yes, the capacitor bridges two terminals on the power switch. It's purpose is for initial supression when turning the amp on, from what I gathered, reading through the related thread.

So, it appears that I should look for a .01 uF (rather than .001 uF) 500V capacitor, correct?
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Old 14th February 2013, 07:24 PM   #6
DF96 is offline DF96  England
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The actual value is not too critical. Anything from 1nF to 10nF will do. The Class X rating is more important. The main purpose of the cap is to suppress arcs when switching off, but it may also provide a small amount of mains filtering during normal use. Normally it should connect across the mains transformer secondary, but best to copy whatever was there before.
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Old 14th February 2013, 07:55 PM   #7
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Thank you both. I did'nt know anything about Class X rated capacitors.I'll be sure to specify same when ordering. I'm glad to have posted here, as I don't want to destroy this old amp.

I wonder if "Class X" even existed when this amp was built. The new capacitor could be a nice improvement over the original.
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Old 14th February 2013, 08:35 PM   #8
oz7aff is offline oz7aff  Denmark
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The capacitor has nothing to do with the amplifier. The capacitor is there to kill the spark that comes when the power switch is opened.
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Old 14th February 2013, 09:23 PM   #9
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I just spoke with a Mouser tech. He was not able to find a .01 uF 500V Class X rated capacitor.
Would anyone know of a suitable substitute available through Mouser? Is it possible to use a higher voltage capacitor?
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Old 14th February 2013, 09:38 PM   #10
DF96 is offline DF96  England
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Don't worry about 500V DC rating - that was the old cap. In the days before X rating they had to use a fairly large DC rating.

In Europe a Class X cap will be rated at something like 275V AC, but perhaps less than that for the US? I'm sure you will find suitable caps in any good catalogue. As I said, the actual value does not matter too much.
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