How To Find Internal Short

[amirrr_22]

Hi,

I have a Kenwood DNX521DAB which will not power on. I have tried to bench test it by supplying power to the yellow and red wire of the harness and connecting ground to the black but my power supply goes into protection mode.

I suspected that there is a short somewhere in the wiring harness but all tests show that this is not the case. I removed the harness from the unit and using a multimeter in continuity mode, I pressed one probe onto the power pin and one probe onto the ground pin and it shows that there is constant continuity. I even placed one probe on the chassis of the unit and the other probe on the power pin and again it shows that there is constant continuity.

When I remove the fuse from the unit, then there is no continuity between the power pin and ground pin. I then placed a probe where the fuse goes and one side shows continuity with ground and the chassis. The other side of the fuse holder shows continuity with the power pin.

Is this normal? Any advice would be greatly appreciated.

 

[(*steve*)]

There are several possibilities.

A simple one is that you (or someone else) connected the power backwards and an internal protection diode has failed short circuit.

However it could be a whole suite of things. You need to open the device up and look for something that is obviously damaged. If you can't find anything, you'll need to find it by other means.

Once you've opened the unit up, take some good pictures and we can help in the search.

 

[amirrr_22]

There are several possibilities.

A simple one is that you (or someone else) connected the power backwards and an internal protection diode has failed short circuit.

However it could be a whole suite of things. You need to open the device up and look for something that is obviously damaged. If you can't find anything, you'll need to find it by other means.

Once you've opened the unit up, take some good pictures and we can help in the search.

Thank you for your response. I have opened the unit up and I may have found the culprit, however, I could be wrong. There is a diode near the power input which I believe is letting current travel in both directions. When using the multimeter in diode test mode, it is displaying 000 in both directions.

Please confirm if my suspicions are correct.

 

[(*steve*)]

I'm not able to review the pictures at the moment, but if that is confirmed it is a great indication that power was applied incorrectly. It is also a reasonable indication that the device has been protected.

You need to remove that diode, test it out of circuit, and replace it, before carefully applying power with the correct polarity.

 

[amirrr_22]

I'm not able to review the pictures at the moment, but is that is confirmed it is a great indication that per was applied incorrectly. It is also a reasonable indication that the device has been protected.

You need to remove that diode, test it out of circuit, and replace it, before carefully applying power with the correct polarity.

Thank you for helping me so far. Later today I shall be replacing the diode and will report back of the results. Fingers crossed!

 

[amirrr_22]

I'm not able to review the pictures at the moment, but is that is confirmed it is a great indication that per was applied incorrectly. It is also a reasonable indication that the device has been protected.

You need to remove that diode, test it out of circuit, and replace it, before carefully applying power with the correct polarity.

Good news!

I replaced the diode in question and the unit started to work again. Thank you so much for the help you provided.

 

[Tha fios agaibh]

I think Steve deserves an attaboy and a "like" click for his helpful post.