Please watch the youtube for repair: https://www.youtube.com/watch?v=xdTP5gev3Ew
The failure mode is cannot power up. Root cause is due to supply to digital board supply NG. Changes D15, Q10, R77, R37 and Q16 (no need change as it still working). and set back to normal.
Note the cover is rusty and remove it and polish it to remove rust, then paint it with silver pen.
This set cannot powder on and due to supply issues. Get it cheap for SGD$30 SGD and come with remove control.
Changed 3 fuses EV+5V, +12V and -12V, one mosfet on primary, and two fusible resistors on SMPS boards, then it can power up and working fine!
All metal edges painted again to prevent rusty and grease a bit inside. As usual, clean up all the dust inside the set.
Owner claim power on unstable and need to wait some time before it can power on. DAC use for this is PCM1716 and sound quite good.
The case metal edges is rusty and thus paint it with silver ink pen. Top DVD board and bottom main board is clean by ultra sonic and some magic clean solutions. After assembly, still cannot work or power on. Later found switched 5V voltage low, touching the regulator output pin is unstable voltage. Then found the cold solder joint. Thus resolder the whole power supply boards again. Stable voltage can immediately power on the set. The alps power switch also shorted and replaced by a new one. Color also missing after repair power board and later trace to a switch transistor NG. Replaced it with MMBT3904 and 1.5k resistors as no stock switch part and working well. Side B track 0 and 1 a bit jam and cause the track jump back and repeated short period. remove and grease it a bit better, may be need alignment again!
DVD is not working and will eject disc. Anyway no point to repair it as DVD player can be as cheap as $10 sgd today!
There is issue on the preamp claim by owner and cannot be used. Later find out that output has about 20-40V DC level drifting. Root cause is due to Jensen output leaking, changes to other film cap resolve the issue.
This is a faulty subwoofer and need repair, after check the pcb, it has been repair trial and see regulator transistor poorly soldered and loose joint. PCB trace on the pcb is weak and need careful repair and touch up all joints. First attempt is power amp board working but oscillation after plug in the pre and crossover boards. Later identified that the capacitors of +/-15V supply weak or not function properly. Thus replace all the E-cap on this subwooder and all working fine. Lesson learn is that Harman use cheap China capacitors and cause the problem not able to last.
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