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Old 13th November 2012, 02:28 AM   #1
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Default New to amp repair and the forum

.Hello everyone,

I am new to the board and look forward to picking your brains. LOL

I have a few amps that I am trying to repair. I am new to amp repair, but have been working with car audio for years.

The first amp is an Ample Audio 4 channel A410x, it does not turn on. I got it from a friend years ago and was told that the problem was that someone had touched the Pos terminal with the ground wire. all the Fets look ok and the amp doesn't show any sings of problems.


The second amp is a Zapco Ag 350 that has some blown Fets but I'm not sure of the numbers on them, so if anyone has that info that would help tons. One side of the amps board got wet and has seems to have shorted out the the Fets.

I am looking for any advice on idea to fix them. I have a few other amps with problems as well, but they will come later after I have figured out how to fix these. they all have different problem witch should give me a verity of lessons.

Thanks in advance for any advice.
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Old 13th November 2012, 03:52 AM   #2
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Welcome, may I suggest you look for any of Perry Babin's posts and then click on the links in red under any of his thread posts. It will take you to his training web-site. And many of your questions will be answered by the wealth of info he has put together for your learning experience. Take it at your own pace, and enjoy.. We will all be here from time to time...
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Old 13th November 2012, 05:21 AM   #3
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Use this thread for the ample audio amp. Post a photo of the inside of the amp.

Start a new thread for the Zapco. Contact Zapco to see if they will release the diagram.
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Old 13th November 2012, 09:55 PM   #4
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Can anyone ID these mosfets?
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File Type: jpg 2012-11-13_13-24-54_32.jpg (543.0 KB, 38 views)
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Old 13th November 2012, 10:23 PM   #5
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Here are some pics of the Ample Audio board. Any ideas would be helpful.
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File Type: jpg 2012-11-13_13-23-28_514.jpg (805.4 KB, 32 views)
File Type: jpg 2012-11-13_13-24-54_32.jpg (543.0 KB, 30 views)
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Old 13th November 2012, 10:47 PM   #6
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Never use NTE parts in a car amp.

The NTE parts are not the original parts. With 100 ohm gate resistors, I'd guess the original FETs were IRFZ44s or something similar.

There are likely 2 more power supply FETs on the other side of the amp.

The two fully encapsulated components next to the NTE parts are the rectifiers.
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Old 13th November 2012, 10:55 PM   #7
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Yea they look like they had both been replaced. If I replace these is it needed to replace the ones on the other side of the board?
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Old 14th November 2012, 12:01 AM   #8
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Quote:
Originally Posted by SlappinM30 View Post
Yea they look like they had both been replaced. If I replace these is it needed to replace the ones on the other side of the board?
If you are lucky just replacing the mosfets will fix the problem.

If you arent so lucky then the reason the mosfets went might still be there.
Sometimes there is a problem further back in the circuit like the driver stage VAS and/or LTP. So powering up with new mosfets will simply blow them all again. Fuses are rarely fast enough to save mosfets.

You could try powering up with a lamp in series with a 13.5 volt DC power supply and see if the lamp lights. That is a common trick and cheaper than a full set of mosfets.
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Old 14th November 2012, 12:14 AM   #9
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What will happen if I us the light? Should I replace all the mosfet with ones that match the ones on the other side of the amp (IRF244N's)?
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Old 14th November 2012, 12:15 AM   #10
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I also made some bigger test leads and now the protection light does come on, but it pulses.
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