# Help with amp repair!



## HerrNuki (May 9, 2014)

Hello all amp is Boschman psx 2 when I got it it was burning fuse after power is applied to remote so I found that it had 3 of 16 burnt output stage mosfet's.
http://i1074.photobucket.com/albums/w410/HerrNuki/IMG_1355_zpseb9bddea.jpg
They were "IRF9640" mosfets. I have removed them and tried to start amp to see did I solved the problem and check for rail voltage but then when I was measuring rail voltage on this little board something poped and I saw it was smd transistor with 1D mark on it. I have marked it in blue in the picture. I would like to know can it be it blowed that little transistor because I started it without mosfets or something other is wrong with the amp?
What is that board for anyway?
Those resistors marked in red get very hot after 5sec amp is turned.
I have 80v on rail and I thing that power suply is working as it should now I just wait for mosfets to arive.
http://i1074.photobucket.com/albums/w410/HerrNuki/ajsdpajsda_zpse2ce7917.jpg
http://i1074.photobucket.com/albums/w410/HerrNuki/IMG_1358_zps6c812c3b.jpg


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## ATOMICTECH62 (Jan 24, 2009)

That is a Maxsonics clone.When the outputs go bad it usually always damages the 6 larger smd transistors on each side of the board.The 8 pin IC's can be damaged also.The board will need to be rebuilt before replacing the output mosfets.
It is normal for those resistors to get hot.Thats why they are the larger 2 watt case style.

There are a few threads on this driver board over on DIYaudio.It is a common failure and is dealt with in detail.


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## HerrNuki (May 9, 2014)

Thank you for your reply, can you please post some link for those threads I can't find any of them.
Is there a way to check those IC's?
When I was desoldering mosfets I saw that half of them are IRF9640 and other half of them are IRF640N can it be they were replaced before or it is a common combination?


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## HerrNuki (May 9, 2014)

anyone??


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