[TenTec] TT 940 Power Supply

[Jim Brown]

On Wed,9/17/2014 9:02 AM, denton sprague wrote:
> an update…..I strapped my Omni 7's ground to the negative line to my Astron 30 amp switching supply….I also installed two ferrite clamp on chokes on the dc lines on the inside of the power supply.

Something else to look at in the Astron.  I've never seen an Astron 
switcher, but I've had a bunch of Astron linear supplies over the years, 
and every one I've opened up was built with a bonding failure. 
Specifically, the green wire from the AC cord goes to the mounting lug 
of a terminal strip. The negative side of DC is also tied to this point. 
BUT -- the terminal strip is insulated from the chassis by paint. This 
would cause RFI to the regulator in a linear Astron, and would cause an 
Astron switching power supply to radiate noise on both the power cable 
and the DC cable.

An easy test for this -- disconnect the DC output cable and measure from 
the power cable green wire (the round pin) to the chassis. You should 
see a few tenths of an ohm for the length of the power cord. If you 
don't, you've got that bonding problem.

The fix is easy -- just remove the screw, scrape the paint, and reinstall.

One of my linear Astrons had an additional shielding failure -- the two 
pieces of the chassis failed to make contact because there was paint 
between them. Same solution -- scrape the paint along the junctions.

73, Jim K9YC