Kenwood kac - x521 major problem

[arazs5]

i have a kenwood exceleron kac x521...it came out of one vehicle and sat in a cabinet for a while...when i re-installed it in another car the two 30A fuses blew a couple seconds after hooking everything up.i have a very basic knowledge of electronics, and i have a multimeter...where would the best place to start be?

[mike49504]

Souns like the power supply is blown in the amp.

First thing you should check is the power supply fets in the amp.

Set your meter to ohms and stick your red probe on leg 1 and stick your black probe to leg 3. Then leave you black probe on leg 3 and stick your red lead on leg 2 (middle leg). You should not red anything near 0 ohms.

Post your results on all of the power supply fets.


leg1 to leg3:
leg1 to leg 2:
leg2 to leg 3:

The image below is a diagram on how to check them
Basic Amplifier Repair - Transistor Test Applet Link

[Perry Babin]

Did it blow the fuse only after the remote voltage was applied (head unit turned on) or did it blow the fuse without remote voltage applied?

[arazs5]

blew them when remote voltage was applied

[Perry Babin]

That probably means that the output transistors are shorted. Q132-Q140 are the output transistors.

[arazs5]

i haven't tested anything yet, but say the output transistors are the source of my problem, is that something i could replace relatively cheap...where do i get components like that??

[Perry Babin]

The parts appear to be available but they're not cheap. Expect to pay ~$30 for the parts if nothing else has failed. PacParts, Kenwood Parts and MCM would be the distributors most likely to have the replacement outputs.

[arazs5]

here's some new insight to my potential problem...i opened up the amp got the board flipped around and found these burns...any insight???

[jol50]

The transistors sometimes puke soot out the legs like that, will usually clean off. Get the numbers off them and look at MCM. I have the best luck there for those SK Sankens they often are. Those are the outputs. I found some at Littlediode also.

[arazs5]

i plan on using the amp bridged...is there some odd chance are there unused transistors that i could just "swap" for the burnt up one?? hard to find anyone selling just one skc3856...i was just curious before i bought a new one or 10 to make my minimum...or are there other components i should consider replacing while i'm in there??