Harman Kardon AVR 1610 review: Well-priced but underachieving AV receiver - CNET
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Troubleshooting Hkts System - Harman Kardon HKTS 200/230 SUB Service Manual [Page 5] | ManualsLib
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Harman Kardon TS-7 Subwoofer - Wont come out of standby - Assistance to troubleshoot (have schematics) : r/AskElectronics
Basically, all Harman Kardon amplifiers (including subwoofers) show power supply issues after a few years « The Wiert Corner – irregular stream of stuff