User Guide

1
SK-401 “SOFT KEY” INSTALLATION INSTRUCTIONS
PARTS SUPPLIED WITH THIS KIT:
(1) SK-401 “Soft Key” Circuit Board Assembly
(2) 6-32 x ¼” Round Head Screws
(1) Nylon Threaded Spacer
(1) #6 Internal Tooth Lock Washer
To start the installation, read these instructions very carefully. Now unplug the amplifier
and remove any input, output and control cables that may be connected to the back of the
amplifier. Place the amplifier upside down with the rear panel facing you and remove 6 screws and
the bottom cover. You are now ready to proceed with the installation.
( ) The exact mounting location of the SK-401 is not too critical. Be sure to keep the RED and
BLACK leads as short as possible. The most convenient place I have found is just behind
(or next to, depending on your version of the L-4B RF deck) the 24 volt supply terminal strip
on the right side near the ON-OFF rocker switch. Try to align the unit such that the BLUE
wire is nearest the wiring harness and the flat part of the large HEXFET transistor is facing
the front of the RF deck.
( ) Once you have decided on a location, mark a location where the large hole in the SK-401
is. This is where the mounting spacer attaches to the SK-401 and also the location of the
hole for the mounting screw. Very carefully drill a hole that will clear a 6-32 screw at the
point you just marked (#27 drill). Do not use too much pressure because you want the drill
to stop after just penetrating the chassis. Clean up any burrs from the hole.
( ) Place the #6 lock washer onto one of the 6-32 x ¼” screws and place the screw through the
hole you just drilled. Screw the threaded nylon spacer from the SK-401 kit onto the screw
and tighten well without stripping the threads in the spacer.
( ) Mount the SK-401 circuit board onto the nylon spacer using the other 6-32 x ¼” screw.
Position the board as previously described.
( ) Unsolder the WHITE & BLUE wire from the antenna relay jack on the back panel.
( ) Remove the diode that is between the antenna relay jack and a small 1-lug terminal strip
next to the jack. You can discard the diode. The lug should not have anything connected
to it after you removed the diode
( ) Route the BLUE and YELLOW wires from the SK-401 along (or in) the wiring harness so
that both wires end up near the antenna relay jack.
( ) Solder the YELLOW wire and the WHITE & BLUE wire (unsoldered from the antenna jack
earlier) to the terminal of the 1-lug terminal strip next to the antenna jack. This effectively
connects these wires together.
( ) Solder the BLUE wire from the SK-401 to the antenna relay jack. This wire will be attached
where the WHITE & BLUE wire was unsoldered from earlier.