I couldn't help but notice that sanyo m-9998 has smashed through the 1000 dollar barrier. So notes the sanyo boom box dealer from the 1970's. Fearing the possibility of the accidental conversion from boom box to non-working "parts set" he sees fit to reveal some key tips that are unique to this model. TIP 1 There is a screw behind the band select knob and one behind the volume knob. These must be removed in order to remove the chassis from cabinet. The service manual does not mention this. TIP 2 Belt replacement. I can't talk you through but I can tell you that I never remove transport assy. Transport is accessible after moving amp board up out of the way. Please get a copy of service manual for this model. It has many wires and plugs that can fit in the wrong place. TIP3 Sometimes when main capstan belt fails, it at some point got wrapped around motor drive pulley, stalling the motor. The high current condition may have caused the 120 ohm 2 watt resistor to open. The symptom is , motor does not turn. Other failures can cause this problem but this resistor sticks in my memory. You should visually inspect it even if functions are ok. If it is discolored, replace it. It is located on the AMSS pcb,This is the board mounted right on tape transport . Use extra care when working on this board. There are a few wires with pin connectors and they are not clearly marked. # This is the same pcb that power wires from cabinet back connect to. Tip 4 Symptom Bass is distorted when volume is increased. Almost sounds like blown speakers. This is caused by the breakdown of the coating that sanyo used on the cloth speaker surrounds, not the glue that holds the cloth to the paper cone. This was a chronic problem in the day and would occur in a few years. We would just replace the speakers. This is a real task on the m-9998 as the drivers are mounted from the front of cabinet. The fix I used when the drivers became NLA is to get a bottle of clear nail polish, the type that remains mildly flexible when dry. A thin coat applied on the cloth roll surround of the speaker from the back will restore factory performance.I know there are many roads to rome on this topic but shy away from the treatments that remain tacky or add thickness to the surround. OTHER NOTE The m-9994 with the paper edge woofers has the same defect and can be corrected by applying a light coat on the pleated surround from the back of speaker.
