Blown Rockford Fosgate 250M, help a newb =-)

[mkfosgate]

I work at a audio/detailing/tinting place, and in the electronics bay that had a few amps that were blown, and the RF 250m was one of them. But, I took the amp apart and found that the little black mosfet chip was blown. Well, one of them closest to the power and ground has a burn mark on it with some suit around it. I was wondering if I just replace that, if the amp should work again, or if there are other things that need to be checked.

When I was in there, I noticed a tiny surface mount resistor that was for some reason, not attached on one side. I just pushed it down, and resoldered it.

Please help me out. The RF guys are going to get me the correct shcematic monday, so I should be able to see what part numbers are on these circuits. Also, I am fairly good with a multimeter, so if you can just guide me threw this, I would appreciate it. I will attach a picture of the board so you can see what I am dealing with.

 

[mkfosgate]

Here is a pic. How do you get the rest of the mosfet chip off?!

 

[mkfosgate]

Here is another. This one, you can see the third resistor up the middle. That is the one that had come up on one side. I jsut pushed it back down, and resoldered it.

 

[mkfosgate]

I dont think the pics were going to show because of them being too big. Here they are again.

 

[mkfosgate]

The other.

 

[Cal Weldon]

To post a pic click on the browse button at the bottom of the window.

 

[jaycee]

No pictures, but to answer your question, it is unlikely that replacing the blown mosfet will fix the amp. There will be further non-visible damage.

 

[mkfosgate]

Try this again. How do I get the rest of that chip off?! lol

 

[mkfosgate]

Heres the other. The original pics I was trying to upload were too big. The resistor 3rd up from the bottom is the one that I pushed the one side back down, and resoldered it.

 

[I Am An Idiot]

To remove the rest of the transistor you will need a small butane torch. Lowe's sells a Bernzomatic brand torch and a small can of butane for under 20 dollars. You will also need some medium size Binder Clips available at Office Depot. The binder clips are required to keep the next component from separating from the thermal strup when you heat the component to be removed. Do not use a plumbing torch. As stated earlier there is probably something that caused the power supply transistor failure. Shorted output transistors are the most likely candidate for that. When the supply failed, it probably took out the gate resistors and possibly the pnp driver transistors that drive the FETs.

 

[mkfosgate]

Can you point out what those peices are, and how to test them? Im guessing using a multimeter would work?

Also, I tried using a heat gun, and just getting the heat right on that mosfet peice, and it seemed to start bubbling around the peice, but it never came off.

 

[Perry Babin]

There have been several rockford repairs. If you want to do a little light reading, perform the following search.