Dead amp..nothing burnt, but visible orange crust. - diyAudio
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Old 2nd October 2006, 05:25 AM   #1
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Default Dead amp..nothing burnt, but visible orange crust.

My amp died about 3 months ago and i finally got around to taking it apart to look at the board. I am not very experienced with working on board, but am studiing electrical engineering in school and know a little about this stuff.

None of the caps seem to be bulging, and all the transistors look in good shape, haven't tested them yet. Could the crust be because of early faliure from the caps? And the system when before they could buldge.


Also what is the best way to test the mosfets without removing them from the board.

Attached is a pic of the amp. its an audiobahn a2300hct.
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File Type: jpg hpim0316.jpg (79.7 KB, 178 views)
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Old 2nd October 2006, 05:34 AM   #2
singa is offline singa  Singapore
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Hi,
The orange crust is leftover flux residue.(Not thoroughly cleaned).Check mosfet pins with multimeter probably shorted.

Power off!
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Old 2nd October 2006, 01:55 PM   #3
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Which pins should i check? I did a quick test not sure what i was looking for and found some mosfets having a resistance of 0. Are those the shorted ones? A whole row of 4 on each side had this. I would have to replace all four on each side correct?
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Old 2nd October 2006, 03:39 PM   #4
TO-3 is offline TO-3  Peru
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Quote:
Originally posted by marcello7x
Which pins should i check? I did a quick test not sure what i was looking for and found some mosfets having a resistance of 0. Are those the shorted ones? A whole row of 4 on each side had this. I would have to replace all four on each side correct?
A 0 ohm resistance would indicate that one ore all four of the devices has shorted. You must replace them all as if one goes, the other try to pick up the rest but it only stresses out the other remaining parts. You may be able to just swap the parts and be done with it or there may be another problem that caused the parts to fail. I did not look at the pic but I am assuming that they are power supply mosfets. Either they had inadequate heat-sinking or there may be a problem in the audio section.
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Old 2nd October 2006, 04:25 PM   #5
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The amp worked fine till i had run the subs to 1ohm or less. They were theoretically at one ohm, if the speakers were rated correctly, which i found out they almost never are. I am going to check the mosfets when i get home from school tonite and give an update then.
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Old 10th October 2006, 01:12 AM   #6
Bose(o) is offline Bose(o)  Canada
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Why don't we run our speakers at lowly resistances? So we don't blow our amplifiers!
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