[TenTec] TT 940 Power Supply

[Bob McGraw - K4TAX]

You raise a point regarding "industrial grade sine wave ups".   I have one 
of those and in my chasing a noise issue, I opened the case to find the 
output receptacles each have the neutral terminal {white wire} and the 3rd 
pin ground terminal {green wire}connected by a solid strap.  This then says 
the neutral is connected to 3rd pin ground at several points, both on the 
input and output.  I seem to recall this is not correct according to NEC.

Anyway, I removed the straps and my noise went away.  Now, this does leave 
the 3rd pin AC ground terminal on the LOAD side of the UPS connected to the 
3rd pin ground on the INPUT side of the UPS.  The neutral however is not 
connected from the LOAD side to the INPUT side, thus there is significant 
isolation between input and output of the UPS.  As it should be in my 
thinking.

Is there some UL requirement, say UL1499, or other international standard 
that I'm not aware that mandates the load neutral and 3rd pin AC must be 
bonded?  It has been too many years since I worked in this part of the 
safety discipline.

Comments anyone?

73
Bob, K4TAX





----- Original Message ----- 
From: "denton sprague" <denton at oregontrail.net>
To: "Discussion of Ten-Tec Equipment" <tentec at contesting.com>
Sent: Tuesday, September 02, 2014 12:36 PM
Subject: Re: [TenTec] TT 940 Power Supply


Ok….I installed a no 10 wire between power supply and Omni 7….that seems(?) 
to have cured the problem.
No chopped the 3rd pin ground….I got everything in the shack tied to a 
industrial grade sine wave ups running on a dedicated 20 amp circuit.
speaker is on the right of the rig….also have a little astron ss30 and a 
huge astron 50m linear power supply that I used to use for entire station.
No rf hash for any of the laptop chargers so far…
On Sep 2, 2014, at 10:13 AM, "Bob McGraw - K4TAX" <RMcGraw at Blomand.net> 
wrote:

> Do you have a solid ground wire between the supply and the radio?  If not 
> the radio is about 1/8 to 1/4 volt above DC ground.
>
> You haven't chopped the 3rd pin ground have you?   For safety reasons, it 
> must be in place.
>
> Some have reported with the supply on the left it makes noise, on the 
> right it does not.  I may have my left's and right's reversed.  Anyway, I 
> think you get the idea.
>
> The ONLY noise I have from a switching supply is from the charger for my 
> laptop computer.  I've purchased three different ones.  All produce noise.
>
> As to the station supply, I use Astron SS-30M's or SS-25's.  Have three 
> and all are quiet.
>
> 73
> Bob,  K4TAX
>
>
>
>
> ----- Original Message ----- From: "denton sprague" 
> <denton at oregontrail.net>
> To: "Discussion of Ten-Tec Equipment" <tentec at contesting.com>
> Sent: Tuesday, September 02, 2014 10:43 AM
> Subject: Re: [TenTec] TT 940 Power Supply
>
>
> Well darn…
> my 940 has a traveling growling noise on 80 meters….wonder if there is an 
> easy fix?
> Otherwise will sell the darn thing….
> On Aug 29, 2014, at 11:36 AM, Ralph Arnold <rea.papaof10 at gmail.com> wrote:
>
>> I'm interested in PS for my Pegasus will it handle it and how much $$ 73
>> KD8BTQ  Ralph
>>
>>
>> On Fri, Aug 29, 2014 at 1:17 PM, Charles J. Nagel <cnagel at sbcglobal.net>
>> wrote:
>>
>>> I have four TT switching power supplies I use for various rigs including
>>> Ten-Tec and Elecraft. Never a noise issue. One is a recently acquired 
>>> 940,
>>> a perfect match for the Omni VII, in my opinion.
>>>
>>> Charles, K0CW
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