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Kenwood KR-9400 Still Blowing Fuse

A

alucia3

New Member
I bought a KR-9400 knowing it wasn't working and I'm trying to repair it myself. I replaced the transistors (all 8 on both heat sinks) but it still blows fuses. I noticed two of the MPC71 resistors are also blown. I read through the service bulletin, and my unit doesn't have the same jumpers and capacitors listed (J2 or Qe3, etc ).

Does the video provide a clue as to the source of the short/open circuit?https://photos.app.goo.gl/gpqWQAXuYvbcvHBZ6
 
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Yikes, your first problem is you are powering the unit up on line power. Don't do that. You need a current limiter, interpose current with a dimbulb tester. Lots of information here online youtube etc about building a dimbulb tester. You need one before you proceed with anything else. Don't blow any more fuses, you are asking for trouble.
 
Did you not check any other transistors other than the outputs for shorts? You're not using a DBT?

The video shows nothing other than the fact you probably shouldn't be working on this unit, since all I saw was the magic smoke come out.
 
Warren-Oates said:
Yikes, your first problem is you are powering the unit up on line power. Don't do that. You need a current limiter, interpose current with a dimbulb tester. Lots of information here online youtube etc about building a dimbulb tester. You need one before you proceed with anything else. Don't blow any more fuses, you are asking for trouble.
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Hello, I’ve been running a repair shop for a few years now, relatively new to the repair world, at least publicly. I’ve always been a self starter, so therefore there are going to be things that I miss.

I appreciate you mentioning something about the dimbulb tester, because I am also in the same position as the author of this thread. Thankfully nothing was blown from me, but from the person that brought the 9400 to me (1 resistor is blown with little sand particles in the right side heat sink). I’ve never worked on one before, but I told the owner of it that i can at least take a look at it, and try to find some info online about it, and see if I can get this thing working.

Is there any way I could ask y’all a few questions about the unit i have currently?
 
Welcome!

Right channel sand resistor? I think you might mean the emitter resistor? If so, it would suggest to me that the output transistors are blown (shorted) along with drivers, pre drivers and bias resistors. Check these components. Also look for burned traces and a few bad capacitors in the same circuit.
 
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