[Amps] RF on audio using 374A

Carl km1h at jeremy.mv.com
Wed Sep 14 11:00:08 PDT 2011

Sorry but I put most so called Pin 1 problems in the same category as 
mysterious parasitics requiring nichrome to cure.

RF on the coax outer shield caused problems as far back as vacuum tube days 
and the ferrite has worked ever since its use was discovered as the first 
and usually the only step needed.

Ive yet to even bother to look for a Pin 1 problem as RF in the house simply 
does not exist to a level to cause a problem with radio, computer or audio 
equipment. IMO Pin 1 is overblown (as are parasitics by another individual) 
and I would expect any of the radio manufacturers to already be aware of it.


----- Original Message ----- 
From: "Jim Brown" <jim at audiosystemsgroup.com>
To: <amps at contesting.com>
Sent: Wednesday, September 14, 2011 11:25 AM
Subject: Re: [Amps] RF on audio using 374A

> On 9/14/2011 6:19 AM, Carl wrote:
>> Glad to hear it wasnt a Pin 1 problem Roger (-;
> Ah, but it most likely WAS a Pin One Problem, and the choke to keep RF
> off the line was the easiest fix.  Think, Carl, about HOW the RF on the
> coax shield gets into the equipment!
> The way equipment is built makes Pin One Problems more likely, AND very
> difficult to fix without a complete rebuild. So the easiest solution is
> to kill the current that excites the Pin One Problem, which is what
> Roger did.
> 73, Jim K9YC
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