Harbach “Soft Key”
(sk-220)
Installation Instructions
for the
Heathkit SB-220
Step-by-Step Instructions with Photos
Based on an install by
W4HDM
Installation & Photos by W4HDM
Instructions from http://www.harbachelectronics.com/
SK-220 SOFT-KEY MODULE
The SK-220 is an easy to install interface module which allows your
transceiver to key the SB-220 seeing only 0.7 volts at 1.5 mA. The
original SB-220 circuit had +120 volts on the keying line.
W4HDM "SoftKey" Install 2
Parts
A. (1) SK-220 “Soft Key” Circuit Board Assembly
B. (1) 6-32 x ¼” Round Head Screw
C. (1) Nylon Threaded Spacer
D. (1) Each - Red, Dark Blue and Black Wires
D
B&C
A
Tools
Straight Head Screwdriver (long)
Wire Cutters/Stripper
¼’ Socket w/Ratchet and Extension
Soldering Iron
Solder
Flux
Book
W4HDM "SoftKey" Install 3
Your Soft Key board may not have the wires connected when
you receive it. If not, strip about 1/8thof an inch back on each
wire (both ends)
Insert wires from the top of the board and solder from the
bottom. Dip the tips in flux and get a little solder on the tip of
the iron. Then briefly touch the iron tip to the end of the wire
sticking through the board. Do not overheat.
Red
Hole
Black
Blue
Hole
W4HDM "SoftKey" Install 4
Instructions
The following instructions are from Harbach Electronics website.
Any of my comments will be in red text.
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 on a book, front panel up, and
remove the bottom screws holding the feet and case in place.
This removes any pressure from the screws caused by the
weight of the amp, if you do not do this it will cause difficulty, if
not damage, while removing the screws.
Place book under here.
W4HDM "SoftKey" Install 5
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