Alpine MRP-F300 amp is dead, need help with repair - diyAudio
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Old 18th October 2010, 02:23 AM   #1
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Default Alpine MRP-F300 amp is dead, need help with repair

Well I have had this amp for almost 2 years now. One day it just stopped working. Diagnosis: receives power, light turns on, no output to speakers. I tested with different signal inputs and still no output.

I don't know where to get started. A while back a Mr. Perry Babbin helped me with another amp of mine and it worked great. I hope you will see this Perry and help me again. Here are some pics.

http://img155.imageshack.us/img155/2416/dscn1235l.jpg
http://img818.imageshack.us/img818/9669/dscn1237.jpg
http://img98.imageshack.us/img98/274/dscn1238w.jpg
http://img297.imageshack.us/img297/4057/dscn1239.jpg
http://img411.imageshack.us/img411/7721/dscn1240y.jpg
http://img199.imageshack.us/img199/8550/dscn1241m.jpg
http://img231.imageshack.us/img231/1010/dscn1242.jpg
http://img87.imageshack.us/img87/2577/dscn1245.jpg

Last edited by gexamb; 18th October 2010 at 02:35 AM.
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Old 18th October 2010, 02:28 AM   #2
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Does it have both positive and negative rail voltage on the center legs of the output transistors?
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Old 18th October 2010, 02:38 AM   #3
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are those the big MOSFETS up top of the picture? I just test the center leg with ground with a dmm right?
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Old 18th October 2010, 02:52 AM   #4
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The transistors in the larger cases are not MOSFETs. They are bipolar transistors. Those are the ones you'll check the voltage on.

Place the black meter probe on the amplifier's ground terminal. Place the red meter probe on the point where you need to measure the voltage.
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Old 19th October 2010, 08:43 PM   #5
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The top transistors are all 9.3v, the bottom left ones are 9.3, and the bottom right ones are 11.3. Refer to the picture for a better look.

Although I did not see any negative polarity. My dmm usually has a neg sign next to the voltage reading. Am I supposed to switch the probes around to check for neg polarity? (Red to ground, black to pin?)

Are these the transistors you were talking about? see below
Attached Images
File Type: jpg dscn1235l copy.jpg (186.4 KB, 104 views)
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Old 19th October 2010, 09:22 PM   #6
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What is the DC voltage on the first leg of the power supply FETs? They are the 4 transistors with 11.3v on the center leg.
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Old 20th October 2010, 02:29 AM   #7
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Actually the power FETs are 11.6v all around not 11.3v. I take it the first leg is the very left one looking at it from the picture I posted. All FETs show 0v exactly and to make sure I also checked the other legs as well (the very right ones) and they were 0v as well.

Also, the other transistors I originally checked also have a negative polarity of 9.3v all around.
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Old 20th October 2010, 02:34 AM   #8
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See attached.
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File Type: gif diytransistor.gif (2.6 KB, 87 views)
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Old 20th October 2010, 02:36 AM   #9
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I just figured it out. The legs are numbered on the PCB, lol. They are all 0V.
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Old 20th October 2010, 02:41 AM   #10
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Post the DC voltage for each pin of the driver IC (..494). Place the black meter probe on the amplifier's ground terminal. Place the red meter probe on the point where you need to measure the voltage.

IC#
Pin 1:
Pin 2:
Pin 3:
Pin 4:
Pin 5:
Pin 6:
Pin 7:
Pin 8:
Pin 9:
Pin 10:
Pin 11:
Pin 12:
Pin 13:
Pin 14:
Pin 15:
Pin 16:
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