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Re: [TenTec] ESD - Static Discharge revisited OMNI VII

To: "Ten Tech Reflector" <tentec@contesting.com>
Subject: Re: [TenTec] ESD - Static Discharge revisited OMNI VII
From: "Jim Brown K9YC" <k9yc@audiosystemsgroup.com>
Reply-to: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Date: Wed, 23 Jul 2008 18:53:33 -0700
List-post: <tentec@contesting.com">mailto:tentec@contesting.com>
On Wed, 23 Jul 2008 19:40:06 -0400, Bill Mellema wrote:

>I now have a new OMNI VII which I really like ..however I noticed 
>again that walking across my carpeted office and touching the mike 
>connector caused the receiver to quit. If I recycle the power it is 
>fine again. I had this problem with another OMNI VII I owned and 
>never could get it straightened out. I am running a ASTRON 55 AMP 
>power supply with the chassis ground going back to the OMNIVII's 
>chassis ground (I did this after the ESD problem was first noticed). 
>I have since measured the resistance from the OMNI VII's chassis 
>ground and the mike connector and the 1/4 inch CW and Headphone 
>jacks. They are all above ground which I think is the problem. Heck 
>you can ground the radio but what does it do if the front panel jacks 
>aren't grounded?

I don't know anything specific about this particular radio, but you're 
right, it is EXTREMELY BAD DESIGN for a cable shield to not be 
connected directly to the chassis. What you describe is known in the 
world of pro audio as "a pin 1 problem" (because pin 1 of XL connectors 
is the cable shield), and is well known as a MAJOR cause of hum, buzz, 
and RFI. The Omni V is FULL of pin 1 problems. So is my FT1000MP. 
Indeed, MOST ham gear has a pin 1 problem at most of its audio and 
control inputs and outputs. Don't know about later Ten Tec rigs. 

Another question, however. Is your rig grounded?  It should be -- in 
fact, it should be grounded both to the power system and any station 
ground should have a good, low impedance bond to the power system 
ground. This MIGHT help, but if you do, indeed, have a pin 1 problem, 
you really need to fix that first. 

There's a lot of tutorial material on my website that discusses the pin 
1 problem in detail.   http://audiosystemsgroup.com/publish 


Jim Brown K9YC

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