[Hammarlund] HQ-129X, tuning LSB

[Roy Morgan]

At 08:40 AM 3/31/2004 -0500, John M. Trindle wrote:
>I finally have my 129X up and running, after killing it last year while
>trying to address AC voltage on the case (still a problem, and I belive
>folks told me it was probably bad capacitors in the power supply section).


John, and others:

I extract the section of my diatribe on capacitors relating to line cords 
and bypass caps for your information:

Line cords and how to install one safely:

(in US standard line cords):
GREEN is safety ground, and should be tied directly to the chassis.
In European (IEC) cords, the safety ground is Green/Yellow.

BLACK is "hot" or "line" - it goes directly to the rear of the fuse holder, 
the terminal farthest from the outside of the fuse holder where the cap is 
installed.  The terminal on the fuse holder nearer the chassis or panel 
goes off to the switch and should go nowhere else.  If you use an open 
clip-style fuse holder under the chassis, use either end of it.

WHITE is "neutral" and goes UN-fused to the system, e.g. power transformer 
primary.  Do not put a fuse in both power cord lines. This can lead to a 
dangerous situation, though it's less likely to be dangerous with a three 
wire grounded line cord than with the deadly fused two-wire un-polarized 
line cord plug.

On the line cord wall plug,
  - the round, longer pin is green
  - the larger flat pin is neutral
  - the narrower flat pin is line or hot.

Note that European color coded line cords have different colors..  Here 
they are:

LINE            (US) Black  =  (EU)  Brown
COMMON   (US)White  =  (EU)  Blue
GROUND    (US) Green     (EU)  Green/Yellow.


(begin extract from message by Bob Nickels)
From: "Robert Nickels" <w9ran@oneradio.net>
Subject: [Johnson] Fused Plugs
...
A good source of replacement 3-wire power cords are those used by computers
and peripherals, but most of them use the European color designations   For
years, the colors of individual conductors in cords for use in North America
have been black for line, white for neutral, and green for earth (ground).
But in order to harmonize worldwide standards,  two major UL equipment
standards, UL 1950, Information Technology Equipment, and UL 2601, Medical
and Dental Equipment, started several years ago to require the more
traditional European conductor color coding: brown for line, light blue for
neutral, and a  combination of green and yellow for ground.

The color conversion is as follows:

LINE            (US) Black  =  (EU)  Brown
COMMON   (US)White  =  (EU)  Blue
GROUND    (US) Green     (EU)  Green/Yellow

(end extract from message by Bob Nickels)

Older HP and other test equipments were equipped with an oval line cord 
connector and matching cord.  The Belden/Volex 17280 power cords are 
apparently the normally-connected cord.  In all of them, the offser 
(center) pin is chassis ground.  There is a version with reversed line and 
neutral. When working with these equipments and line cords, do take time to 
sort out hot from neutral so you retain the safety aspects of the fuse 
connection.


RF Bypass caps should be installed as follows:

One from Line to Neutral, after the fuse.
One from neutral to chassis.

Do not install one from line to chassis and neutral to chassis as was 
normally done years ago.  This causes a danger of fire should the line to 
chassis cap short but not draw enough current to blow the circuit breaker, 
and this arrangement also causes the chassis to be at half the line voltage 
if the safety ground is not present (such as in a two-wire outlet used with 
an adapter, or in an outlet improperly wired or faulty.)

There are currently available "Safety" capacitors meant for line bypass 
applications. You can tell them from normal caps in the catalogs because 
they cost about 5 times as much as normal caps.  If you take apart computer 
power supplies or junk TV sets, you will wind up with one or two from each 
unit.

Live Safe
Live Long

Roy




- Roy Morgan, K1LKY since 1959 - Keep 'em Glowing!
7130 Panorama Drive, Derwood MD 20855
Home: 301-330-8828 Work: Voice: 301-975-3254,  Fax: 301-948-6213
roy.morgan@nist.gov --