TenTec
[Top] [All Lists]

Re: [TenTec] TT 940 Power Supply

To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>, <denton@oregontrail.net>
Subject: Re: [TenTec] TT 940 Power Supply
From: "Bob McGraw - K4TAX" <RMcGraw@Blomand.net>
Reply-to: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Date: Tue, 2 Sep 2014 14:21:23 -0500
List-post: <tentec@contesting.com">mailto:tentec@contesting.com>
As many times you will read from my posts that a dedicated ground should exist between the power supply ground and the radio ground. Although Denton seems to confirm adding a ground did correct his concerns, I have found in some cases it does not. In other cases it does improve RFI issues.
What I typically find can be confirmed by using a DVM and measuring the DC 
voltage between the power supply ground and the radio ground.  In transmit 
mode, CW key down, the transmitter is drawing maximum current.  By measuring 
the voltage between power supply ground and the radio ground one can then 
determine just how much above ground, i.e. the zero volt point, the radio 
exists above ground.  Typically I find anywhere from 0.125 to 0.250 volts to 
be the value.  By adding a dedicated ground between the power supply ground 
and the radio ground this value drops to near zero volts.  Although the 
current is much less in receive, the amount of  effective series R exists in 
both receive and transmit.
In most cases today the DC negative and the power supply ground are 
connected at some point internal to the power supply.  Some may agree this 
is correct and some may disagree.  Personally, I prefer to have DC negative 
and power supply ground to exist at a common point inside the power supply. 
Also this is the same point where the 3rd pin AC ground is attached.  I also 
suggest one investigate to assure that the method of attachment is not 
electrically violated by paint on the chassis.  If you suspect such, just 
lift the connection point, use a bit of #100 sandpaper and remove the paint 
around the attachment point until bare metal is exposed.  Then using proper 
hardware, which includes an internal tooth lock washer to bite into the 
metal, reconnect the DC negative, the chassis ground and the 3rd pin AC 
ground.  And while you have the cover off, check to see the upper part of 
the cover and the lower part of the cover again are not insulated from each 
other by paint.  Just clean it off where the screw holes are located on the 
inside edges and again use an internal tooth lock washer as part of the 
assembly process.  This assures the covers are electrically connected.
If you have a switching supply that causes noise, the above may correct all 
of your concerns.
73
Bob, K4TAX






----- Original Message ----- From: "denton sprague" <denton@oregontrail.net>
To: "Discussion of Ten-Tec Equipment" <tentec@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@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@oregontrail.net>
To: "Discussion of Ten-Tec Equipment" <tentec@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@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@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
_______________________________________________
TenTec mailing list
TenTec@contesting.com
http://lists.contesting.com/mailman/listinfo/tentec

_______________________________________________
TenTec mailing list
TenTec@contesting.com
http://lists.contesting.com/mailman/listinfo/tentec
_______________________________________________
TenTec mailing list
TenTec@contesting.com
http://lists.contesting.com/mailman/listinfo/tentec




_______________________________________________
TenTec mailing list
TenTec@contesting.com
http://lists.contesting.com/mailman/listinfo/tentec
_______________________________________________
TenTec mailing list
TenTec@contesting.com
http://lists.contesting.com/mailman/listinfo/tentec




_______________________________________________
TenTec mailing list
TenTec@contesting.com
http://lists.contesting.com/mailman/listinfo/tentec

<Prev in Thread] Current Thread [Next in Thread>