User manual HARBACH ELECTRONICS MM-220

[. . . ] Rem ove the 2 Phillips-head screws on the right side of the front panel. Remove the 2 Phillips-head screws on the left side of the front panel and loosen the front pane l. It may require a slight prying action with a screwdriver to separate the front panel from the chassis due to paint stickage. Pull out the pilot lamp assem blies from each meter. [. . . ] 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. Th e drill will tend to drift into the larger (old) hole. A small rat-tail file would be useful in cleaning up this hole. 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). Remove the tem plate from the panel and trial fit the new meter. 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. W e will now reas semble the front panel. 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. Loosely install the mounting washers and nuts. 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). Loop the BLACK meter wire through the "-" terminal of the meter. [. . . ] Now reinstall the 3 large and 2 sm all knobs. The tuning and loading capacitors each point directly to the left (9 o'clock). The sensitivity po te nt io m eter points at 7 o'clock and the meter switch knob points to "GRID". Replace the perforated cover and top rear plate cover. [. . . ]