Altec Lansing, Inc. is an American audio electronics company that primarily produces loudspeakers and associated audio electronics for professional, home, automotive, and multimedia applications.
The large round multi pin plug as to make good enough connection to supply power and often doesn't with age. Wiggle it until it at least flashes the light r you give up. If it does the issue is that connector pair.
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post some pictures inside for us to see.
Front PCB and and Back PCB
Do you have a multimeter?
If unsure, bring it for a friend or shop to check.
Augustine さんによる