User Guide

2
( ) Replace the perforated cover and top rear plate cover. Reinstall the 15 sheet metal screws
holding these pieces in place. DO NOT over tighten these screws, as it is fairly easy to
strip the screw threads in the aluminum underneath.
( ) Use the book to hold the amplifier while you reinstall the case and feet.
This completes the installation of the SK-220 “Soft Key” module. You may not SEE any
difference in the operation of your exciter or amplifier, but you will know that you have reduced the
stress on the exciter’s keying relay by many orders of magnitude.
SK-220 “SOFT KEY” MODULE
HARBACH ELECTRONICS
Jeff Weinberg – W8CQ
468 County Road 620
Polk, OH 44866-9711
[phone]
http://www.harbachelectronics.com
[e-mail]
PARTS LIST
R1 & R2 100KΩ ½W 5%
R3 10KΩ ¼W 5%
C1 & C2 0.1µF 50VDC CERAMIC
D1 1N4005 (1A 600 PIV)
D2 1N60 GERMANIUM
Q1 MPS2222
Q2 IRF610 HEXFET (N-CHANNEL)