SB-840R TS-830S Frequency Shift 04-14-82 Some users may report an intermittent shift in the display and operating frequency. This may typically be a 1 to 4 kHz random shift. Cause will be a loose grounding screw on the AF/AVR unit heat sink. On the AF/AVR unit X49-1140-00, there are three self-tapping screws holding the aluminum heat sink to the PCB. These also supply the ground connection to that section of the board. Between the heat shink and PCB foil, add a toothe-lockwasher N17-1030-41 at eht two self-tapping screws on the side of the heatsink that has the two transistors attached. (The remaining screw already has a lock washer.) When replacing the board to the chassis, add a solder lug E23-0420-05 to the heat sink mounting screw as shown, and tighten all screws for this board. Solder an insulated lead between the TPG (Test Point Ground) wrap post adjacent to C81, and the added solder lug. Procedure: 1. Remove the top cover (8 screws) and unplug the speaker. 2. Remove the bottom cover (8 screws). 3. Remove 5 screws holding the AF/AVR unit and swing the board over. Leads do not have to be unplugged. 4. Add two tooth-lock washer as shown. 5. Replace the circuit board and heat sink to the chassis, adding the solder lug as shown. 6. Solder a jumper between the TPG wrap post and the added solder lug. 7. Replace the top and bottom covers. Installation time for this procedure is 1/2 hour or less. JEB/yn (c) 41482TKC