[Amps] [RFI] Amp causing RFI

[Jim Brown]

On 2/5/2020 7:24 PM, Mark Schoonover wrote:
> My
> 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.

http://k9yc.com/PowerSupplyBondingAndAudioDistortion.pdf

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