[TenTec] Station power supply??

[Mike Hyder -N4NT-]

The  way I grounded the negative lead was to remove the insulators from the 
contact bolt and clean the paint from around the hole INSIDE the chassis, 
then added a star lockwasher inside the chassis and threw the insulators 
away. I never experienced any more trouble.

73, Mike N4NT

----- Original Message ----- 
From: "Jim Brown" <k9yc at audiosystemsgroup.com>
To: <tentec at contesting.com>
Sent: Tuesday, September 04, 2012 11:36
Subject: Re: [TenTec] Station power supply??


> On 9/3/2012 8:25 PM, Mike Hyder -N4NT- wrote:
>> 1ST CHECK YOUR AC OUTLET GROUND IT MUST HAVE GOOD CONNECTION
>>
>> 2ND. MEASURE FROM THE -13.8V TERMINAL TO CHASSIS, IF NO DIRECT 
>> CONNECTION,
>> RUN A PIECE OF WIRE FROM -13.8V TERMINAL TO CHASSIS.
>
> Damn!  This advice is fixing a manufacturing problem that I found in all 
> three of the Astrons I own -- the green wire in the power cord that IS 
> REQUIRED BY LAW TO GO TO THE CHASSIS for safety, does NOT make that vital 
> connection. The reason is simple, and a common manufacturing defect -- the 
> green wire is soldered to the chassis lug of a terminal strip that is 
> INSULATED from the chassis by PAINT!   In one of the three units I own, 
> the two pieces of the chassis were also insulated from each other by 
> paint.
>
> Bonding -12VDC to the chassis causes a problem when powering a SSB rig 
> that SOUNDS like RFI, but is NOT RFI.  W8JI pointed out this problem to me 
> several years ago. Ohm's Law causes IR drop in both V+ and V- conductors 
> that varies with SSB modulation.  Nothing new. But when V- is bonded to 
> the chassis, and when audio accessories are running from that same supply, 
> the modulation of V- is added to the audio. That modulation SOUNDS like 
> SSB in an AM detector -- it SOUNDS like RFI.  But it's not.  You can hear 
> this modulation if you connect headphones between one end and the other of 
> the V- conductor of your power supply wiring.
>
> I have long advocated bonding chassis to chassis for all equipment in our 
> ham shacks to minimize problems with hum, buzz, and RFI. This practice 
> also reduces the above problem to the point where it is not audible. .
>
> 73, Jim K9YC