If the cap case is truly grounded you should not be able to cause an arc to
the rack cabinet assuming the cabinet is also grounded...
So it sounds as if the cap is arcing internally to its case which is the
capacitor breaking down. You might extent the life of the cap by insulating
the case from ground. Please know that this is a dangerous practice.
To be sure the cap is discharged you would then ground the case and then
both terminals before servicing.
Best solution if you are certain the noise is from the cap is to plan on
replacement.
And be extra careful of oil caps anyway. They have a nasty habit of
recovering a charge over time. That's why you should store these caps with
the terminals shorted together.
wa4tuk
-----Original Message-----
From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com]On
Behalf Of JimMoci@aol.com
Sent: Thursday, February 20, 2003 9:53 PM
To: amps@contesting.com
Subject: [Amps] HV Capacitor arcing problem????
Hello all~
I am having a problem with my homebrew amplifier and am looking for some
advice. It is a 4-1000A amp in a rack with the HV power supply mounted to
the
bottom of the rack.
As of late I started to hear an intemittent snap or arc. After some
investigation I discovered that this arc was coming from the side of the
metal case of my 32uF 4500V oil filled GE cap (it is not coming from the
screw terminals). It just seems to arc to the bottom of the rack cabinet and
happens anywhere from every 5 to 10 minutes. It is mounted with a bracket to
the bottom of the rack which is painted steel. I sanded the paint down to
bare metal to be sure there was a good electrical connection and this has
reduced the frequency of the arcing. Unfortunately when it does arc now, it
is an even louder SNAP! I even soldered a ground strap to the cap and
grounded it to the chassis with no effect.
What do I do next ???
Thanks for any and all suggestions,
Jim
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