Please see the attached schematic.
KD-2schematic.pdf
I've been working to restore this unit and find there is no idle bias voltage. the unit will pass signal with no load. It will also pass signal when loaded with an 8Ω load, but at a bias voltage of 16mv, Q711 begins to run away and overheat, leading to failure.
I have replaced these components which either failed or read bad on DVM:
Q710, 711, 708, 718, 719, 720, 721
R 759, 757, 729, 751, 749
I've also had to hand-wire a number of connections due to pads lifting from the board.
All the silicon components read good in circuit and resistors and diodes are within spec. I expected to find some idle bias voltage measured across R751 or R749, but no voltage appears until a signal is inserted with the amp under load.
I reckon I've overlooked something, likely on the Q711 side of the unit.
I'd be very grateful for any help offered.
Regards,
Steve
KD-2schematic.pdf
I've been working to restore this unit and find there is no idle bias voltage. the unit will pass signal with no load. It will also pass signal when loaded with an 8Ω load, but at a bias voltage of 16mv, Q711 begins to run away and overheat, leading to failure.
I have replaced these components which either failed or read bad on DVM:
Q710, 711, 708, 718, 719, 720, 721
R 759, 757, 729, 751, 749
I've also had to hand-wire a number of connections due to pads lifting from the board.
All the silicon components read good in circuit and resistors and diodes are within spec. I expected to find some idle bias voltage measured across R751 or R749, but no voltage appears until a signal is inserted with the amp under load.
I reckon I've overlooked something, likely on the Q711 side of the unit.
I'd be very grateful for any help offered.
Regards,
Steve
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