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Old 11th May 2001, 03:14 PM   #1
Eric is offline Eric  United States
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Hi Everyone: I'm ordering parts for my Pass a40 amp and have gotten to the part where I need to find AC power cords and connectors. I stumbled across some EIC receptacles that contain RFI filtering and was wondering about using this instead of just a "regular" power input. Any comments or pro's and con's I should be aware of with these?

Thanks for your help!
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Old 11th May 2001, 10:25 PM   #2
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Default You need it!

Get a real one with filtering.

They are actually intended for protecting the net from garbage generated inside your device (such as switching diodes etc.). They come in various flavours. I put one in my CD player -- one of the bigger upgrades I have done. I also got a totally awesome one and put in my poweramp -- same thing happened.

Consider getting one with a ground inductor if you connect to ground -- in Norway we don't usually have ground in our living rooms, so I have not tried those.

I have previously posted more under "X100 backengineered" under solid state forum, about page 3 or so.

Petter
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Old 15th May 2001, 01:08 PM   #3
Eric is offline Eric  United States
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Lightbulb Thanks for the links

Hi Petter: Thanks for the links! I looked up the Corcom website, plenty of good material there. It looks like the Q series is the only one that will handle over 10 amps, but they're pretty pricey - near $100. They're also pretty large. I like the size (and power switch) of the C series, maybe I'll have to look into those as well...

[Edited by Eric on 05-15-2001 at 08:26 AM]
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Old 15th May 2001, 03:10 PM   #4
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Corcom units are typically rated at spikes of 6 times rated current.

120V, 10A -- how much heatsinking are you planning to use???

Check out the units at MECI as well.

Petter
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Old 15th May 2001, 03:46 PM   #5
Eric is offline Eric  United States
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Default Heatsinking & Current Draw

Petter: The amp will probably only draw 2-3A under normal conditions (dissipate ~100wpc), but what I'm concerned about is the ability of the filter to handle the inrush current to charge 96,000uF of capacitance. The inrush capability of the C series is listed at 51A, so this should be OK.

As for heatsinks, I've got 8 Wakefield 423A units, rated at 0.67c/w each. This gives a total heatsinking of 0.0837c/w, where the original design calls for 0.125c/w so I've got a little margin of safety... I just like to over-engineer a little - makes me feel better that things won't blow up as quickly.
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Old 15th May 2001, 06:07 PM   #6
Jon T. is offline Jon T.  United States
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Try putting a thermistor in series with the transformer primary. On turn on, the resistance will be high, limiting inrush current, but will fall as its temperature rises.

Another method I've seen is to put a power resister in series with the transformer and shunt it with a normally open relay. After 20-30 seconds, a timer closes the relay.

51A of inrush current is going to put a strain on every part of your power supply, not to mention probably pop your circuit breaker.

-Jon
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Old 15th May 2001, 06:22 PM   #7
Eric is offline Eric  United States
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Question Misunderstanding

Jon: I don't know what kind of inrush current will occur as a result of the filter caps, which is why I was looking for higher rated filters... I wasn't implying that the inrush current will actually BE 51A, just that the RFI filter could safely handle up to that amount.

In this case, I'd suspect the filter would be pretty comfortable handling whatever inruch happens with powerup. However, the thermistor isn't a bad idea at all. Thanks for the tip!

Eric
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Old 15th May 2001, 08:34 PM   #8
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Default Cost of filters

Hello,

If you check the surplus market, can find filters ranging from 1 amp to 30 amps. Some brand new, some used. Usually for 30% or so of new cost.

Places such as:

All electronics - http://www.allelectronics.com/
Apexjr - http://www.apexjr.com/
MECI - http://www.meci.com/
and dozens of others.

Regards,
Greg
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Old 16th May 2001, 01:07 AM   #9
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You should buy a good on because there are a lot in the market that donīt much. The good ones are usaly large in size. Donīt get anything chinese or so.
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Old 16th May 2001, 01:42 PM   #10
Eric is offline Eric  United States
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Thumbs up Thanks!

Thanks for all of the help! Sounds like something I should definitely do. I'll look around and see if I can find a good one surplus.

Eric
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