Alpine MRV-F353 Problem - diyAudio
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Old 2nd January 2012, 03:39 AM   #1
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Default Alpine MRV-F353 Problem

Ok all 5 channels work, but the sub channel has weak audio and measures 27.76 Volts DC on sub out terminals , all fets and drivers check to be ok in circuit
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Old 2nd January 2012, 08:29 AM   #2
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Post a photo of the inside of the amp.
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Old 2nd January 2012, 02:01 PM   #3
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Old 2nd January 2012, 09:28 PM   #4
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You stated that it has 27v DC and produces audio. Do you have a capacitor in series between the speaker and the amp or did it push the cone fully in/out when you connected the speaker?
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Old 3rd January 2012, 01:23 AM   #5
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pushes the cone fully out with no signal
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Old 3rd January 2012, 01:28 AM   #6
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When you checked the smaller transistors, did you just check to see if there were any reading 0 ohms?

You may have one leaking. Check them carefully. If one reads lower than you think it should, pull it out of the circuit and re-check it.
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Old 6th January 2012, 10:27 PM   #7
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Is the D718 transistor N-channel or P channel? and same question for B688 transistor those are the output mosfets
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Old 6th January 2012, 11:13 PM   #8
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Neither is N or P-channel. These aren't FETs. The D718 is an NPN. The B688 is a PNP. They are both BJTs (Bipolar Junction Transistors -- or simply bipolar transistors).
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Old 8th January 2012, 10:39 PM   #9
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both small transistors between output transistors...seem to check good checked several times and saw no leakage
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Last edited by bigpun4fubu; 8th January 2012 at 10:42 PM.
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Old 8th January 2012, 11:30 PM   #10
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Those are the bias transistors. They rarely fail. The readings look OK.
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