Trying to repair a Kenwood DNX9990HD

[tibimakai]

I have picked up another Kenwood. It's a nice unit but something happened to it, because I have found some blown PCB fuse(made out of copper layer), some trace it's blown, a diode is cracked and the power IC(LV5680) is getting very hot.
Any input on the copper layer fuse? Can I just solder in a SMD 5A fuse?
I'm having a hard time identifying the diode's marking. I have found on the board other diodes with marking 47. This one it looks like a 47? I have found some Infineon diode, but not sure if is the right one.
There is a trace that is blown, I will have to run a wire to make contact again.
The power IC most likely has to be changed, am I right?
Here are some pictures:

[999999999]

Re: Trying to repair a Kenwood DNX9990HD

Yes something, likely the LV5680, is blown and that has caused excessive current assuming no other problems are present like a short on the speaker output from frayed speaker cables or similar.

Yes you can solder in a 5A fuse, but I wouldn't do anything further until after you have replaced the fault component (probably LV5680 as stated above) or else you will just blow the fuse.

You can try gluing down the blown trace between the two resistors but I would go ahead and add a piece of single strand solid jumper wire to replace it.

As for the diode I can't see the markings in the picture. If it is the same physical size as the other diodes marked 47 then it does seem most likely it is the same part # diode used there. Measure the package size then look at what is available in that size at electronics supply houses, it's probably not something exotic so I would focus on what the typical current capacity is for something around 100V rating and get the highest voltage rated part that doesn't drop the current rating to increase the voltage rating in that package size, but of course the safer course would be to measure the voltage at that point in the circuit or look at what voltage the power supply itself produces since the voltage is only going to get lower from there.

[tibimakai]

Re: Trying to repair a Kenwood DNX9990HD

Thank you for the reply.
I have run a wire as suggested.
I have placed the order for the power IC.
The diode marking seems like it's 47, but if I look up smd 47 diode it seems like it should be a dual BAS40-07 which has a SOT143 package(4 pin), which doesn't seem right.
The other diodes used on the board are 24, A2 and H7.
Somewhere else I have found that it also could be a fast switching diode. I have to find it again. I think it was an Infineon diode.

[tibimakai]

Re: Trying to repair a Kenwood DNX9990HD

I have just remembered that I have lower end Kenwood unit from same year and I have opened it up and there it is the diode in the same spot same markings, 47.
47 could be a UDZS4.7B?
http://www.digikey.com/product-detai...76787012784420
I guess, I will have to measure that unit's diode, when it's turned on and see if there is 4.7V at that pin.

[999999999]

Re: Trying to repair a Kenwood DNX9990HD

If all else fails, measure the size and get the highest current diode available in that size with 100V rating or higher. Diode size is related to heat dissipation but the forward voltage (loss) isn't very different so current rating dominates the size vs dissipation factor.

[tibimakai]

Re: Trying to repair a Kenwood DNX9990HD

There has to be a difference between a regular diode and a zener one, no?
Nothing bad can happen if I put a regular diode instead of a zener diode?

[999999999]

Re: Trying to repair a Kenwood DNX9990HD

You would have to supply a complete circuit diagram for me to be sure it isn't a zener diode, but it seems unlikely that it is. It does not look like one and a competent screening architect would label a zener as ZD... so, you roll the dice and take your chances.

[tibimakai]

Re: Trying to repair a Kenwood DNX9990HD

Just to be sure, I will measure the other Kenwood unit.
There is a service manual available, but it's $20. I try not to get it if we don't really need it.
Here is the data sheet of the zener diode and there is no ZD marking on it:

[budm]

Re: Trying to repair a Kenwood DNX9990HD

If it is Zener diode for regulating the + supply, you can check and see if the ANODE is connected to Ground and the Cathode is connected to the current limiter resistor, one end of the resistor will be fed by + voltage. Need more pictures to see how this diode is used.

[tibimakai]

Re: Trying to repair a Kenwood DNX9990HD

I will just take a measurement when I will have a little bit of time on the DNX6990HD unit.
Most likely not today. Need to pick up another LG TV, maybe two. Still have to deal with the one I already have.

[tibimakai]

Re: Trying to repair a Kenwood DNX9990HD

At that diode on the 6990HD unit I have measured 1.56V. So it's not a zener diode, you were right.
Which diode should a chose?
The size is about 1.63x1.4MM.
Any help would be appreciated.
The IC should arrive on Saturday, I just need a fuse and this diode. I would like to pace the order as soon as possible.

[tibimakai]

Re: Trying to repair a Kenwood DNX9990HD

Just an update.
I have assembled all the boards and still doesn't boot up.
Then I have installed from another Kenwood DNX6190HD the upper board, called video control board and the receiver turned on and showed picture.
So my repair of the lower board-power supply radio tuner-it works.
I have dropped it off at a Kenwood service center and they didn't want to test it further. They just wanted to replace the board that I have just replaced.
So now my only option is to find another broken DNX9990HD and get that board from it. The board is available at pacparts or kenwoodparts, but it's $261.xx.