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Old 6th November 2005, 01:43 PM   #1
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Default mounting bolt = min pole?

Maybe a noob questions that has been asked 100 times before (but I couldnt find it)

I noticed that the M12 mountingbolts of my Rifa PEH169 caps are actually electrically connected to the minus pole of the capacitor. I am bolting these caps on a aluminium chassis of the amp. Can this cause problems???

Of course the minus pole will be connected to ground anyway, but can having the mounting bolt also touch the chassis in some way be harmfull (for people or for the amp)? Its for a Zappulse pwm amp btw.

Btw I have these nylon mounting nuts, but in order to make them isolate I have to make the holes for the mountingbolts 22.5 mm wide. Then the nylon caps canl recede 1 mm into the chassisplate

http://www.elfa.se/pdf/67/06767461.pdf
http://www.elfa.se/pdf/67/06768303.pdf
http://www.svalander.se/shoppen/pdf/...c_appguide.pdf
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Old 6th November 2005, 06:35 PM   #2
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You should isolate the mounting bolts....
First of all because this extra connection could cause a ground loop in single rail amplifiers.
Worse is it in two rail amplifiers (positive and negative supply rails). In the possitive rail, the mounting bolt will be "ground", but in the negative rail, the bolt will be = negative supply. Ground and negative supply connected together = trouble
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Old 6th November 2005, 07:19 PM   #3
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THanx for your reply. I will adapt the holes, so that the nylon cap nuts can be used to isolate the mountingbolds from the chassis.

Click the image to open in full size.
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Old 7th November 2005, 08:27 AM   #4
AndrewT is offline AndrewT  Scotland
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Hi,
is the can connection to negative of the cap a common occurence?

I always thought the can was insulated from the cap and would only conduct if there was a catastrophic failure.

Do you need to bolt the can to the chassis? Try silicone sealer as a glue/insulator. It sticks well to metal work.
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Old 7th November 2005, 03:24 PM   #5
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Normally when the caps are with screw connection, the can it self is isolated
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