SK-201 "SOFT KEY" INSTALLATION INSTRUCTIONS PART S SUPPLIED WITH T HIS KIT : (1) SK-201 "S oft Key" Circuit Board Assembly (1) Nylon Threaded Spacer (2) 6-32 x ¼" Screws (1) 2-Lug Terminal Strip (1) #6 Lock W asher 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 and remove the perforated sheet metal RF shield from the top of the chassis. Remove the tubes and put them in a safe place. You are now ready to proceed with the installation. () Turn the amplifier over so that the rear is toward you. Locate a point that is 8" from the right edge of the chas sis and 4½" from the rear of the chassis. Mark this point. 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. Rotate the chassis so that it is o n its side w ith the transform er down (it is m ore s table that way). Push (1) 6-32 screws through the hole from the tube side of the chassis. Put on a lock washer and attach the nylon spacer onto the screw (on the underside of the chassis and tighten. Inside the tube compartment, locate the screw that fastens the RF shield to the chassis and secures terminal strip "Q" to the underside of the chassis. Terminal strip "Q" is a 5-lug strip mounted at a right angle to the re ar of the chassis. Loosen this screw and remove the nut while keeping the screw through the chassis. Place the hold down lug of the supplied 2-lug term inal strip over the end of the 6-32 screw (the one you just rem oved the nut from). It may require some a djustment of the wiring harness to m ake room for the strip. The strip should be oriented approximately parallel w ith the existing terminal strip "Q". Reinstall the 6-32 nut onto the screw and tighten. Now turn the am plifier over (bottom up). Locate the 33 1W resis tor going from the antenna relay jack on the rear panel to a solder lug at the end of the primary voltage selection strip. Unsolder the res istor from the jack and move the end so that it goes through the insulated terminal on the 2-lug terminal strip you just installed. DO NOT solder yet. Leave the 0.02µF disc capacitor connected to the antenna relay jack. Install the SK-201 circuit board on the nylon spa cer w ith a 6-3 2 x ¼" screw. Orient the circuit board with the long side parallel with the rear of the chassis and the TO-220 transistor away from the rear of the chassis. () () () () () () () 1 () Connect the BLACK wire from the SK-201 circuit board to the grounded lug of the 2-lug term inal strip (installed earlier) and solder. Connect the YELLOW wire from the SK-201 circuit board to the insulated lug of the 2-lug terminal strip and solder (along with the 33 1W resistor). Connect the BLUE wire from the SK-201 circuit board to the antenna relay jack on the rear panel and solder (along with the 0.02µF capacitor). On the terminal strip to the left of terminal strip "Q", locate the junction of the rectifier diode and the 10K 2W resistor. Connect the RED wire from the SK-201 circuit board to this junction and solder. Fish the GREEN wire from the SK-201 circuit board under the capacitor going between terminal strip "Q" and the terminal strip to the left, over the wire bundle and through the grom met in front of the SW R bridge assembly. Rotate the chassis onto its side with the transform er down. Pull the GREEN w ire all the way through the gromm et so that it reaches one of the terminal lugs where the filament choke is soldered. Solder the GREEN wire to one of the lugs where the filament choke is attached. Reinstall the tubes and the perforated sheet metal RF shield on the top of the chassis and put the chassis back into the case. () () () () () () This completes the installation of the S K-201 "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. 2 SK-201 "SOFT KEY" MODULE PARTS LIST R1 R2 R3 C1 D1 D2 D3 IC1 100K ½W 5% 10K ¼W 5% 2K ¼W 5% 100µF 10VDC 1N4005 (1A 600 PIV) 1N5817 SC HOT TKY (1A 20V) 1N60 GERMANIUM 4N33 OPT OCO UPLER HARBACH ELECTRONICS Jeff Weinberg ­ W8CQ 468 County Road 620 Polk, OH 44866-9711 (419) 945-2359 http://www.harbachelectronics.com info@harbachelectronics.com 3 ...