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 Post subject: SME & Corcom Filters
PostPosted: Aug Fri 27, 2021 1:29 am 
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Joined: Jan Tue 07, 2020 1:41 am
Posts: 4362
Location: Belleview, FL 34420
AC/DC sets are normally subject to a lot of noise, however transformer radio are still very noisy with those annoying high level AC hum spots across the dial. I tried a SME filter in the can. It takes a 3 wire plug in cord and two wires without ground to the radio It has the superior two LC sections vs the standard single section. The AC hum noise was greatly reduced across the frequencies to the point it presents no issues. I had no idea of the filter performance.

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 Post subject: Re: SME & Corcom Filters
PostPosted: Aug Sat 28, 2021 2:48 pm 
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Joined: Jun Sat 09, 2007 8:14 am
Posts: 5098
Location: Melbourne, Florida
There are a zillion models of these things. Which one did you use?

RRM


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 Post subject: Re: SME & Corcom Filters
PostPosted: Aug Sun 29, 2021 7:10 am 
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Joined: Jan Sat 25, 2020 5:23 am
Posts: 700
Location: Colorado Springs, CO 80917
Did you install the filter in the radio chassis or sorta "splice it" in line on the cord


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 Post subject: Re: SME & Corcom Filters
PostPosted: Aug Sun 29, 2021 6:03 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 16875
Location: S. Dartmouth MA 02748-1225 USA
Quote:
SME filter in the can
Should be a model number on the can...

The Manufacturer's website will have the full specifications as well as applications, maybe.

Installation is important in critical applications as the filter will be rendered useless unless certain grounding and shielding precautions are not taken.

I try to take the best precautions but ideally an IEC shielded cord set with an IEC male connector on the filter is best. But who wants to make that huge hole in an antique radio chassis :shock:

If used with an AC/DC radio sending back the noise on the 3-wire power cord is also iffy. The power ground at the outlet is NOT a noise sink and can bring noise in via the "U" ground connection.
If it does work in a minimal installation to satisfaction then good.

A point to remember is that there is leakage AC current from the caps inside line to the grounded shell. That shell must return to the "U" ground continuous or the exposed can represents a "tickle" hazard.

I HAVE seen Corcom IEC filter properly installed fail dramatically, actually flame out and blow a hole in the case. The incident was on an analytical device used outdoors. What was suspect was a distant lightning pulse caused the arc over and the local circuit line was fused for some 30 amps, instead of 20. Yes, the internal switching power supply was ruined. But the computer was not harmed...

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 Post subject: Re: SME & Corcom Filters
PostPosted: Aug Sun 29, 2021 7:06 pm 
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Joined: Jan Tue 07, 2020 1:41 am
Posts: 4362
Location: Belleview, FL 34420
I use SME filter in cord, not on chassis.

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 Post subject: Re: SME & Corcom Filters
PostPosted: Aug Sun 29, 2021 7:08 pm 
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Joined: Jan Tue 07, 2020 1:41 am
Posts: 4362
Location: Belleview, FL 34420
Chas wrote:
Quote:
SME filter in the can
Should be a model number on the can...

The Manufacturer's website will have the full specifications as well as applications, maybe.

Installation is important in critical applications as the filter will be rendered useless unless certain grounding and shielding precautions are not taken.

I try to take the best precautions but ideally an IEC shielded cord set with an IEC male connector on the filter is best. But who wants to make that huge hole in an antique radio chassis :shock:

If used with an AC/DC radio sending back the noise on the 3-wire power cord is also iffy. The power ground at the outlet is NOT a noise sink and can bring noise in via the "U" ground connection.
If it does work in a minimal installation to satisfaction then good.

A point to remember is that there is leakage AC current from the caps inside line to the grounded shell. That shell must return to the "U" ground continuous or the exposed can represents a "tickle" hazard.

I HAVE seen Corcom IEC filter properly installed fail dramatically, actually flame out and blow a hole in the case. The incident was on an analytical device used outdoors. What was suspect was a distant lightning pulse caused the arc over and the local circuit line was fused for some 30 amps, instead of 20. Yes, the internal switching power supply was ruined. But the computer was not harmed...

i use a three wire computer cord to filter input. It plugs in the filter.

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 Post subject: Re: SME & Corcom Filters
PostPosted: Aug Sun 29, 2021 7:39 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 16875
Location: S. Dartmouth MA 02748-1225 USA
jimbenedict wrote:
..
I use a three wire computer cord to filter input. It plugs in the filter.
For the ultimate isolation, use a three wire cord (IEC) with a shield, yes, it is the same circuit as the green ground but the shield covers the cord wires and extends noise "immunity" up to the outlet. The shielded cords are hard to find as surplus but they are around. chas

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