Read Harman Kardon ONYX STUDIO 2 (serv.man2) Service Manual online
3.2. +12V failed (TP704)
1. Connect good DC board/ USB board and KB to MB.
2. Set power supply 3.8V, connect to MB J700 and power on; monitor power supply voltage, if voltage
drop close to 0V, it must short at somewhere; otherwise go to next step
3. Measure TP701 voltage and it should equal to 3.8V; if not, J700 is defective.
4. Measure U702 pin8 and it should close to 3.8V, if not R714/ R716 NG.
5. Take off L703 and measure point A voltage, if it still can’t get 11V on L703, it must be something wrong
in below circuit. Otherwise, it must short at some area, checking other part circuit which power is
coming from +12V.
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