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Re: [Amps] [RFI] Amp causing RFI

Subject: Re: [Amps] [RFI] Amp causing RFI
From: Jim Brown <>
Date: Wed, 5 Feb 2020 21:49:30 -0800
List-post: <>
On 2/5/2020 7:24 PM, Mark Schoonover wrote:
Astron has a ground lug on the back and that's connected to the station
ground. It's still grounded to the AC ground for the house.

Maybe not. All of the linear Astron supplies I've opened have the same manufacturing defect, documented by this write-up that I did when I discovered it.

Specifically, the green wire from the power cord is soldered to the mounting lug of an old-fashioned terminal strip, which is insulated from the chassis by paint. V- is also tied to the chassis on that same lug. The result is that the green wire is connected to V- but NOT to the chassis, as required by safety codes. One one rack mount model, the two halves of the chassis were also insulated from each other by paint. All of which makes for a power supply that is a sitting duck for RFI.

My recommendation is 1) scrape the point everywhere that it's preventing contact; 2) remove the bond between V- and the chassis (at that terminal strip); 3) bond the chassis to station ground; and 4) before connecting the Astron to anything, use an ohmmeter to verify that the green wire is making contact with the chassis and V- is not.

73, Jim K9YC

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