6146B Question

[Glen Zook]

What rig is it?

If Japanese and designed for the 2001A tubes, then it
was originally designed for the 6146B and use of them
shouldn't be a problem.  However, if the rig was
designed for the 2001 or if it is of US manufacture
(very few US rigs were designed originally for the
6146B), then the finals could still be a problem.
Tubes do change slightly with operation and spurious
emissions are possible.  Have you tried a new set of
finals?  If not, try them first.

Check ALL of the hardware on the chassis including
that which holds the printed circuit boards in place.
Slightly loosen and then retighten ALL of the screws
and bolts.  Almost all rigs make ground connections
through terminals held in place by screws and these
either become loose or build up corrosion (which you
often cannot see).  Corrosion equals diodes which
equals harmonics.

If there are shielded areas, make sure that all of the
hardware that attaches the shields is in place and
tight. If shield uses the lugs that are attached by
rivets to the shield, move those back and forth on the
rivets to get rid of any corrosion.

In many years of working on equipment I have found
either the use of the 6146B in place of the 6146/6146A
or else loose/corroded hardware to be the problem in
virtually every case.  If the rig was designed for the
6146B, then loose hardware in every case where the
station grounding was proper.

It is possible to have problems in the supression
circuitry go bad, but I have only seen this happen
once in over 40 years of working on equipment (I
started working on radios when I was a sophomore in
high school in late 1959).

Check your station grounding.  Corrosion often builds
up even if you can't see it.  Loosen, "wiggle", and
then retighten the hardware.  Check the wires for
corrosion.  If any present, either "cut back" the wire
or else take a knife, sandpaper, or something else and
clean the surface of the ground wire.

Check your antenna connections.  Again, corrosion
builds up.

Have you checked things using a dummy load?  If TVI is
present using the dummy load then it is definitely
coming from the rig or the grounding system.  If it
isn't, then you have to include the antenna system as
well as the rig and grounding system!

If you have a grid dip meter use it to "sniff" around
the rig looking for harmonics and spurious emissions.
If you don't have a GDO but have a scanner, you can
put the scanner into the search mode and go looking
for harmonics and spurious emissions.  This often
works, but not always due to the nature of spurious
emissions (they can vary in frequency, often at a
rapid rate).

Since I present seminars on various aspects of
grounding I have put a synopsis of my presentations on
the two websites that are listed at the end of this
message.  Of course those articles only hit the "high
lights", but they do give a starting place.  There are
other ways of doing grounding, my way isn't the only
effective method.  But, what I recommend does work and
is inexpensive to install.

I do not recommend the "in-line" type of protection
devices that are "pushed" by certain manufacturers.
They don't usually hurt anything, but there are
certainly other things that work just as well, if not
better, that cost a fraction of the price.  Of course
the recommendation articles on the websites pushing
those types of articles just happen to be those
websites of the people who make the devices!


--- Fred Wittman <wittfa19 at EARTHLINK.NET> wrote:

My old hybrid rig (not a Heathkit - sorry) has begun
putting out horrendous TVI. I figure something in the
supression circuitry has changed value.  How should I
approach troubleshooting this?  The outputs are, BTW, 6146B's.

=====
Glen, K9STH

Web sites

http://home.attbi.com/~k9sth
http://home.attbi.com/~zcomco

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