Question about Nitro BMW-482 Car Audio Amplifier

1 Answer

My Amplifier keeps blowing fuses.

I took out my subs in December and left the amp and wiring as is. Two days ago I went to put my subs back in and the amp would not turn on. There was a blown fuse. I replaced the fuse but the amp blew the new one in two seconds.

I have, since then, taken the amp out of the car, hooked up brand new wires directly to the battery (positive battery terminal to positive input, amp ground to the negative battery terminal), ran a new remote wire and removed all other inputs and outputs from the amp (ie. No RCA inputs from the deck and no speaker load or wires to the subs). It is now an amp with three wires. A power, a remote, and a ground.

The amp STILL blows fuses.

I have taken it apart today. I'm definitely not an electrical engineer; although I wish I knew one. I am looking to see if anything appears out of the ordinary - nothing does. All components look pristine, in tact, and well maintained. There is a circular donut with black, red, and copper coloured wires wrapped around it (all those wires are copper - about 18-20 gauge) I don't know what this is or how to check if it is the problem.

There is a coil with a thick black stick inside of it about an inch long. I don't know what this is, what it does, or how to test if it is working.

Basically, my question is, with this set of symptoms, can anyone come up with a reasonable diagnosis? If the amp is blown, that's fine, but it worked when I uninstalled the speakers in December. So, what could have possibly happened since then to blow the amp? There was no load on it.

Anyway, thanks in advance for the help!

Additional Details 2 minutes ago Model is:

BMW-482 2Ch MOSFET Bridgeable Amplifier
1000W peak

Serial No. 100420199

It turns on for two seconds and seems to be "working" until the fuse blows. Originally when the subs were still connected, it gave the "puh" sound when the power first turns on. This was normal for the three years that I had the amp running perfectly.

I didn't push it to its max either. I never turned it up very loud.

Posted by on

  • jgilchrist Aug 16, 2008

    Thank You! I have located two transistors that read near zero ohms. I am not sure if I am taking correct readings since there are three metal tabs connecting each one to the board.

    I will try to replace these. Is there any way to find identical transistors?

    If this turns out to be the problem, then I am in your debt.



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  • 631 Answers

It probably has shorted output transistors.If it's like many of the Asian amplifiers, the outputs will be larger than the rest of the devices clamped to the heatsink. If you measure the resistance between the legs of any individual output transistor and read anything near 0 ohms, the transistor or one in parallel with it is likely shorted and will need to be replaced. You'd have to remove it from the board for definitive testing.

The donut is a power transformer. The coil with the black stick is an inductor.

The following page will help acquaint you with the components inside the amplifier.

Amplifier Repair Primer

Posted on Aug 15, 2008

  • Perry Babin Aug 16, 2008

    What are the numbers on the face of the transistors?

    If there are 8 of the large transistors in the amp, you may have only one shorted. You'd have to pull them to know for sure.

    Before you do any testing, carefully read the information in the yellow table on the page that I posted.

    Let me know if you have any other questions.


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