Alpine mrv-f300 works fine for 10 min and then audio gets bad - diyAudio
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Old 11th December 2010, 11:04 PM   #1
ivkata is offline ivkata  United States
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Default Alpine mrv-f300 works fine for 10 min and then audio gets bad

I got this amp here Alpine mrv-f300 its a 4 chanell v12 amp.will work fine for 10 min all audio chanels sound great and then distortion and gets worse ans worse.All chanels go bad at the same time ,any info is apresiated
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Old 12th December 2010, 12:35 AM   #2
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What do you mean when you state that 'all channels go bad'? Do the outputs in them fail and have to be replaced?

I'm assuming that you have the transistors clamped to the heatsink.
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Old 12th December 2010, 01:24 AM   #3
ivkata is offline ivkata  United States
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well the amp will work fine for 10 min and will start distortions in all chanels.none of the output tested bad.if i let the amp stay overnight will work aggain for 10 min and the same.all transistor are clamped to the heatsink and none gets hot
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Old 12th December 2010, 01:34 AM   #4
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Power supply issues maybe ???? at least that's what it sounds like with all 4 channels being effected evenly their only common thing is the power supply. perhaps its going into fault and not shutting down and or muting the channels, this would explain the unique symptoms.... Perhaps bad solder joints, thermally intermittent devices in the lower 16 volt regulators. Just sounding some ideas...
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Old 12th December 2010, 02:29 AM   #5
ivkata is offline ivkata  United States
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just had it running for 10-11 min the same story.there is a pair of transistors near the power supply a1220a and c2690a that get kinna hot and i doubt they should couse are not mounted on any radiators,i can smell them hot
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Old 12th December 2010, 02:32 AM   #6
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On the upc494 (or whatever 16 pin IC they're using to drive the power supply, measure the DC voltage on all of the pins before and after it shuts down. Which pins have different voltage after it shuts down?
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Old 14th December 2010, 04:32 AM   #7
ivkata is offline ivkata  United States
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i cant really do that now the amp have desided to play only bad.bad bad bad gate voltage is 0.8 no wonder why shitty audio comes out

kia 494 shows this

Pin 1: 1
Pin 2: 1
Pin 3: 3.8
Pin 4: 0
Pin 5: 1.7
Pin 6: 4
Pin 7: 0
Pin 8: 15
Pin 9: 0.8
Pin 10: 0.8
Pin 11: 15
Pin 12: 15
Pin 13: 5
Pin 14: 5.6
Pin 15: 5.3
Pin 16: 0.00
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Old 14th December 2010, 09:03 AM   #8
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Was the amp producing clean audio when you measured the DC voltage?
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Old 14th December 2010, 05:51 PM   #9
ivkata is offline ivkata  United States
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nope all bad audio now and when i tested the kia494
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Old 14th December 2010, 06:41 PM   #10
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When the audio is distorted, does the amp have both positive and negative rail voltage on the output transistors?

Does it have both positive and negative regulated voltage on the power supply pins of the op-amps?
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