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Old 25th February 2009, 10:14 PM   #1
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Unhappy HELP needed

hi all just changed all output and input transistors on my alpine mrd-605 but still no output what else could i try i only have a DDM at hand just wondering what i could be missing out ,must be something stupid as it powers up with no warnings or faults on the amps display
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Old 25th February 2009, 10:16 PM   #2
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Old 25th February 2009, 10:31 PM   #3
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Is it producing rail voltage?

Do the op-amps have 15v?

MRD-M605?
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Old 26th February 2009, 09:44 PM   #4
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Hi thanks for your reply there is power going to output transistors and input as for the op amp not sure where these are sorry but im just starting out on this stuff gotta start somewhere i suppose here is a link to the insides of the amp could you point me as to where they are thanks so far!! and yea it is the MRD-M605 sorry missed the (M)

http://ampguts.realmofexcursion.com/Alpine_MRD-M605/
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Old 27th February 2009, 03:51 AM   #5
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On the bottom of the board between the RCA and fuse holder, those three 8 leg ICs in a row are likely op amps. Get the number off them and look up the datasheet. They should have the +/- 15v on them, often the end legs have the power the sheet will show you. The ICs like that for the amp section will run off the 15v, amp no work without. Seems like the display would run off it too but not sure. Ground to center tap for that like for rail voltage test.
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Old 27th February 2009, 01:21 PM   #6
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Thanks so far there is 15v going to all 3 of them tried looking for data sheet but no luck here are the numbers of them if intrested 4580 FO338 JRC
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Old 27th February 2009, 01:34 PM   #7
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NJM4580.

You should have +15 on pin 8 and -15 on pin 4.
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Old 27th February 2009, 07:47 PM   #8
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yes pin outputs are correct, should there be a reading on all legs of the inputs leg 1 is 0.20v middle leg is 16.50v and leg 3 has o.oov
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Old 27th February 2009, 07:57 PM   #9
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When you say 'inputs', what are you referring to?
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Old 27th February 2009, 09:11 PM   #10
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hi im talking about the input transistors IRF3205's 4 in total
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