Hello, How long was the unit left on without music playing? Reason I ask is that you probably blew the internal fuse to the subwoofer due to heat if it was left on. To access the fuse you must remove the entire rear of the cabinet to get at the backside of the plate amplifier (where the auto/on switch and connections are located). The fuse will be located within a couple of inches of the transformer and the power cord and would need to be checked with a multi-meter. If the issue goes beyond the fuse (fuse tests good, or replacement fuse does not allow the unit to power up), then the transformer has over-heated and failed and would require replacement which is in the $125 range. For that price you could replace the plate amp with a new one and retro-fit it into the cabinet. The link below is where you can view and shop around for replacement amps to use in the Sony:
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