[Kenwood] Re: Kenwood ts-520 neutralization info

[james27613 at att.net]

hi gordon,

here is a link for you,

http://groups.yahoo.com/group/TS-520_820_530_830/

Here is how to do it,
written by Bill K0ZL, the list founder

There are several ways to neutralize finals in any
hybrid radio (Yaesu or Kenwood). Here is the way that
I have found to be easiest and fastest:

Make sure you have a dummy load connected to the rig.

You will also need a screwdriver with an insulated
shaft, blade about 1/8" wide, shaft at least 4" long.

WARNING: THIS PROCEDURE REQUIRES CONTACT WITH LIVE
ELECTRICAL PARTS USING AN INSULATED TOOL. DO NOT
PROCEDE IF YOU ARE UNFAMILIAR WITH THE SAFETY
PRECAUTIONS IN WORKING WITH HIGH VOLTAGE. THIS
EQUIPMENT CAN CAUSE SERIOUS INJURY OR DEATH.

Unplug the radio and reemove the bottom cover(s) to
expose the lower part of the PA enclosure. Locate the
neutralizing capacitor. This will be a small
air-variable capacitor, usually mounted on the floor
of the PA enclosure with the screwdriver shaft
pointing downwards. Carefully attempt to turn this
screwdriver shaft with your insulated screwdriver.
Free up the capacitor as needed BEFORE powering up the
rig.

Also check to see that the screwdriver shaft is
sufficiently insulated to prevent contact with other
components, chassis ground, or yourself. On some rigs
you may need to move components slightly to make
things more accessible.

Once you have your bearings and the neutralizing
capacitor can easily and safely be turned, power up
the rig.

Tune the rig for low power on 20 meters, keeping plate
current below 150 mA. Quickly tune the PLATE control
for dip; adjust the loading control so that the dip is
noticeable but not too sharp.

OBSERVE the plate current dip as you rotate the PLATE
TUNE control. It should rise smoothly on either side
of the dip, and it should rise about the same amount
on either side. If so, NO FURTHER ADJUSTMENTS ARE
NEEDED; the rig is neutralized.

If not, notice which side of resonance the plate
current rises the most. Adjust the neutralizing
capacitor to equalize the rise on either side of the
plate current dip.

NOTE: This procedure should be done with ONE HAND AT A
TIME; in other words, TUNE the plate; let go, then
adjust the neutralizing cap with the other; let go,
then TUNE the plate again. This will keep the current
paths through your body to a minimum in case of a
mishap (the old keep-one-hand-in-your-pocket trick
will work too).

Once the plate current rise on either side of the dip
has been approximately equalized with the
neutralization adjustment, tune the rig for max output
into the dummy load.

Now rotate the PLATE TUNE control through the dip, and
see if the rig RF OUTPUT is maximum when the plate
current is at minimum, or very close to it. If so, the
neutralization process is complete.

If not, touch up the neutralizing capacitor as needed
to make it so.

Plate current at maximum rig output should dip from
ten to 15 percent. This indicates peak efficiency for
the pi network and longest life for the tubes.

Check also the plate voltage at max output, by using
the rig's built in hi-v meter (if supplied) or by
SAFELY measuring the plate voltage (do this only
OUTSIDE of the PA enclosure; do NOT measure at the top
of the plate choke or you will destroy your meter and
possibly yourself). Plate voltage should not drop more
than  10-15 percent at full output.

Now check neutralization on 15 and 10 meters using the
methods outlined above (either RF output maximum
coinciding with plate current minimum; or plate
current rise on either side of the dip being about
equal). There should be no huge difference. If there
is, AND if one of those is your favorite band, re-do
the procedure on that band. Some rigs do show a
difference from band to band and it's best to
neutralize on your favorite band if that is
preferable).

73

Bill K0ZL