I opened up my 50 amp RM-50 Astron supply this morning and can confirm thick
paint between both the the lug of the line ground (green) wire and also the
chassis connect for the B- line. Thick paint on both sides. Took a dremel
tool and cleaned off the paint on both sides of each lug (i.e., inside and
outside of the chassis). It didn't fix the particular problem I am looking
in to but I sure feel better about it.
Two more Astron supplies to do later this weekend.
Thanks for the information.
73 de Mike
K7PI
-----Original Message-----
From: RFI [mailto:rfi-bounces@contesting.com] On Behalf Of Jim Brown
Sent: Thursday, April 10, 2014 14:24
To: Rfi List
Subject: Re: [RFI] Keurig coffee vs Astron Rs35M
On 4/10/2014 1:58 PM, Hisashi T Fujinaka wrote:
> I know you think you have special knowledge, but it's still one turn
> through ferrite of dubious origin which is NEXT to useless but not
> useless.
Well, I did spend five years studying how ferrite chokes work for RFI
suppression, published it for the first time around 2005, and have updated
it over the years as I've learned more. Much of that material was
subsequently added to the ARRL Handbook.
I don't know about you, but I finished my EE in 1964, and I've been doing me
best to learn SOMETHING every day since.
On one of those days, I opened up the three Astron power supplies in my
station and learned that none of them had the green wire in the power cord
bonded to the chassis, as required by safety codes in most of the developed
world. The green wire was soldered to the chassis mounting lug of a terminal
strip, but the lug was insulated from the chassis by paint. That same lug is
also bonded to V-, so this manufacturing defect would make the green wire an
effective antenna, coupling RF onto the Astron common bus. In the pro audio
world, we call this sort of defect "The Pin One Problem," and it's a well
known cause of RFI, both emissions and susceptibility.
73, Jim K9YC
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