SK-301 "SOFT KEY" INSTALLATION INSTRUCTIONS PART S SUPPLIED WITH T HIS KIT : (1) SK-301 "S oft Key" Circuit Board Assembly (1) Nylon Threaded Spacer (2) 6-32 x ¼" Screws (1) #8 Bent Solder Lug (1) #6 Internal Tooth Lock Washer To start the installation, read these instructions very carefully. Unplug the amplifier and remove any input, output and control ca bles that may be connec ted to the back of the amplifier. Remove the chassis from the case, turn the rear of the amp tow ard you, and remov e the rear panel and left corner piece from the chassis. You are now ready to proceed with the installation. () The exact m oun ting loca tion of the SK-301 is not too critical. Be sure to keep the leads as short as pos sible. The m ost convenient place I have found is just to the left of the filament choke. Turn the chassis over and mark a location approximately 1-1/8" in from the re ar of the chassis and 2-9/16" to the right of the center of the middle U-shaped cutout in the bottom plate of the chassis. This is where the mounting spacer attaches to the SK-301 and also the location of the hole for the mounting screw. The hole should be located nearly under the inside tube sockets. V ery carefully drill a hole that w ill clear a 6-32 screw at the point you just marked (#27 drill). Do not use too m uch pressure because you w ant the drill to stop after just penetrating the chassis. Clean up any burrs from the hole. Turn the amplifier back over. Rem ove the screw directly under the column of feed-throughs located next to the filament choke. Place the 2-hole solder lug over this screw and re-install the screw. Attach the threaded nylon spacer to the SK-301 through the large m ounting hole in the corner of the circuit board using one of the 6-32 x ¼" screws and tighten well without stripping the threads in the spacer. Plac e the #6 lock washer onto the remaining 6-32 x ¼" screw and put it through the hole you just drilled. Attach the nylon spacer (and circuit board) to the chassis. In the following steps, route the wires under the SK-301 circuit board and/or under the filament choke as required. Connect the BLACK wire from the SK-301 circuit board to the solder lug you just installed and s older. Route the GREEN wire from the SK-301 circuit along the chas sis and up into the transformer com partment and c onnect GREEN wire to the right side of the bottom feedthrough (nearest the transformer) and solder. Route the RED wire from the SK-301 under the circuit board and connect to the top feedthrough and solder. () () () () () () () 1 () Remove the small white wire from the center contact of the "antenna relay" jack. Remove the other end of this w ire from the solder post near the coax connec tor. Route the BLUE wire from the SK-301 under the circuit board and connect to the center contac t of the "antenna relay" jack and solder. Connect the YELLOW wire from the SK-301 circuit board to the solder post where the white wire was removed and solder. Note, there is a 39 resistor also connected to this post. Reinstall the left corner piece and rear panel onto the chassis. Place the chassis back into the case. () () () This completes the installation of the SK-301 "Soft Key" module. You may not SEE any difference in the operation of your exciter or am plifier, but you will know that you have reduced the stress on the exciter's keying relay by many orders of magnitude. SK-301 "SOFT KEY" MODULE PARTS LIST R1 R2 R3 C1 C2 D1 D2 D3 IC1 Q1 200K ½W 5% 10K ¼W 5% 2K ¼W 5% 100µF 10VDC 0.1uF 50VDC 1N4005 (1A 600 PIV) 1N5817 SC HOT TKY (1A 20V) 1N60 GERMANIUM 4N33 OPT OCO UPLER IRF9610 HEXFET (P-CHANNEL) HARBACH ELECTRONICS Jeff Weinberg ­ W8CQ 468 County Road 620 Polk, OH 44866-9711 (419) 945-2359 http://www.harbachelectronics.com info@harbachelectronics.com 2 ...