User manual HARBACH ELECTRONICS MM-220

[. . . ] () Remove the 15 sheet metal screws that hold the perforated cov er in place and remove this along with the top rear plate cover. Rem ove the nut and washer holding the band switch to the front panel. Remove the nuts and washers holding the meter switch and sensitivity pot to the front panel. [. . . ] 1 () () () () () () () () () () () () () () () Carefully center punch the new upper right and lower left mounting holes. Drill these holes w ith a 1/16" drill, keeping the drill perpendicular to the panel (a drill press helps, but is not necessary). If you have a 3/32" drill bit, use it to enlarge the lower left 1/16" hole, otherwise carefu lly enlarge this hole with the 1/8" dr ill. Punch through the tem plate near the upper left notch to be cut in the front panel. W ith a sm all rat-tail file make the indicated notch in the meter cutout hole. A triangular file or the edge of a rectangular file may also be used to make the notch (the notch does not have to be round). This w ill indicate whether more filing is needed to obtain a good fit and have the top of the meter parallel with the top of the front panel. W hen a good fit is obtained, fasten the meter to the front panel with the supplied washers and nuts. If the plate meter is being replaced, leave off the washer and nut f ro m th e lo w er left stud (view ed from the rear of the front panel). Unsolder the m ete r leads and bypass capacitor from the solder lugs that went to the old meter. Cut the black and white leads going to the lamp assem bly removed from the old meter. Cut these leads close to the lamp assembly and strip about 1/8" of insulation from each end. Bring the front panel up to the front of the amplifier chassis and put the meter switch and sensitivity potentiometer shafts through their respective mounting holes. Reinstall the meter leads on the meter not being replaced and tighten the meter terminal nuts. If the plate meter is being replaced, place the supplied flat washer over the remaining mounting stud, then the meter light terminal strip and finally the mounting nut. Looking down at the back of the front panel, loop the RED meter wire through the "+" terminal of the new meter (the terminal nearest the right edge of the front panel). [. . . ] The sensitivity po te nt io m eter points at 7 o'clock and the meter switch knob points to "GRID". DO NOT over tighten these screws, as it is fairly easy to strip the screw threads in the aluminum underneath. Reinstall the case and feet using a book to support the amplifier. () () () () () This completes the replacement of a panel meter on your SB-220. [. . . ]