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KRK 10S Subwoofer keeps blowing fuses

danwinter

New Member
Hello all I recently got a KRK 10s that every time I plug in and turn on is blowing fuses. (got it for free knowing it does this). I am feeding it T1.6AL250V 5x20mm 1.6A 250V Slow Blow fuses so I'm pretty sure I have the correct fuse in there. I have a multimeter, know how to take readings, and have experience soldering and am taking this on as my first repair. Based on my research so far I am thinking that problem lies in the PSU. I've opened up the sub and got a good look around and I don't see anything burnt or out of the ordinary. Being that this is my first repair I figured I would consult with some people who know more than me to get a good idea of where to start trouble shooting. I attached some pics of the inside and the diagram for the circuit.
 

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danwinter

New Member
I guess to be more specific too I am curious if I can just test the PSU to see if thats bad. Like each of these boards such as the PSU, the amp, etc. are separated and I can buy replacements. I am not super concerned about replacing individual components on the board if I could just verify that the PSU is the problem I am totally fine with just buying a new PSU PCB and calling it a day. I just want to verify that is the problem before I start throwing in new PCBs all willy nilly. Thanks!!
 

ramondo

Member
The fastest way to narrow down something is to unplug J6B, replace the fuse, plug unit to wall and turn it on. If fuse still blows then there is a problem on power supply board( may also be more) I fuse remains good then problem is further down.
 

danwinter

New Member
OOOO but I just realized when I unplugged J6B although the fuse did not blow when I powered it up again. When I went to plug it back it I noticed some burn mark on the plug and realized the capacitor next to it had blown that I hadn't noticed before.
 

ramondo

Member
It would appear that the schematic is for a different but similar unit.
I believe either c411,12,13,or 14 are the ceramics shown. It is possible that the larger cap is the faulty one and has damaged the c607 cap. A shorted component(either cap) could cause the fuse to blow and second attempt with new fuse caused component to open thereby removing the short. My first suspect would be rectifier KBU602 in 42 volt supply. In circuit resistance reading should be very similar to the one on 20 volt supply.
Since you are looking to replace the defective PCB,best guess is PSU however a short further down curcuit "MAY" have overloaded the PSU to the point of failure.
 

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