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Old 27th November 2006, 02:30 AM   #1
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Default alpine mrv 1505

powers up no output.

where to start? looking from the bottom of the amp with the power cables pointing at your belly....

transistors to the right all the there are first 6
leg 1 - 0.00
leg 2 - 11.8+/-
leg 3 - 11.8+/-

transisitors to the left first 6

leg 1 - 0.00
leg 2 - 11.8+/-
leg 3 - 0.00

transistors 7,8,9,10 both left and right all legs ar between 4 and 6 vdc

tried to post pics... said they were too big... will resize them
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Old 27th November 2006, 06:04 PM   #2
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Default here are the pics

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.
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Old 27th November 2006, 07:23 PM   #3
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Try running a ground wire to the RCA shield from the 12 volt ground. This is just a quick test for a regular issue on these where the internal ground reference has been damaged by overload conditions.

If you get sound with the ground wire then you have a damaged ground reference in the protection circuitry that references both the RCAs and the protection to 12 volt grouind.

seen this about 600 times before, very common issue.

Hope this helps
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Old 27th November 2006, 07:33 PM   #4
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Default great info. thanks.

will try it out. if this is the problem what is the fix?
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Old 27th November 2006, 08:18 PM   #5
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Default Re: great info. thanks.

Quote:
Originally posted by IMPALAMAN1
will try it out. if this is the problem what is the fix?
Well you will need the schematic to tech out the bad ground reference point, so i can't walk you thru that here ( I would hog up too much forum space).

I have seen a simple jumper wire to the ground of the lower rails solve the issue quickly, but there maybe ground loop issues from this sort of repair. If you chose to do this just solder a wire from the 12 volt GROUND, to the ground of the + - 15 volt regulator circuit. This bypass's the original grounding method that Alpine used. The problem will never come back, BUT I make no promises about ground loop noise.
The other solution is to obtain the schematic and tech it out and replace the burnt device in the protection circuitry.

This was caused by abuse to the amp. it has been overdriven to the point that this damaged has occured. The only other possibility is a poor ground for the amp, but that's not what i have seen in the many years these have been around. Oh and by the way all Alpines have this issue, And I do mean ALL Alpines from the Straight and V-12 series. Thay all shared common design in the protection and ground reference area.

Hope this helps
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Old 28th November 2006, 05:59 AM   #6
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Default Re: great info. thanks.

Quote:
Originally posted by IMPALAMAN1
will try it out. if this is the problem what is the fix?
I sent you a e-mail
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Old 28th November 2006, 10:19 AM   #7
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If there are no open traces for the ground circuit, double-check the solder connections on all of the copper buss-bars. This problem should be obvious after you pull the power supply board.
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Old 28th November 2006, 03:50 PM   #8
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Default Perry, pleasure as always

J.O.M.A, tried out your advice, it did and didnt work. so what happend was I powered it up and grounded channel 2 and channel 1. channel 1 kicked on after i pulled the wire away. channel 2 never played. what doesnt make any sense is that the speaker will play on the bridged taps with the channel 1 input only.

the switch for 1+2, stereo, mono doesnt seem to make any difference.


Perry, I will try this tonight.


So at this point im down to the channel 2 output.
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Old 28th November 2006, 07:56 PM   #9
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Default Re: Perry, pleasure as always

Quote:
Originally posted by IMPALAMAN1
J.O.M.A, tried out your advice, it did and didnt work. so what happend was I powered it up and grounded channel 2 and channel 1. channel 1 kicked on after i pulled the wire away. channel 2 never played. what doesnt make any sense is that the speaker will play on the bridged taps with the channel 1 input only.

the switch for 1+2, stereo, mono doesnt seem to make any difference.


Perry, I will try this tonight.


So at this point im down to the channel 2 output.
Take a reading of the DC voltage on the rca shield, as referenced to 12 volt ground. I am sure you will find DC voltage on the shield. I have seen as much as 49 volts on the RCA shield. This was caused by a bad insulator under a output FET. The whole case had 49 volts on it
These are the typical finds on a amp that looks as pristene as yours does.
As for bad traces (like Perry has suggested) I would look back at the very back end of the board near the 12 volt and protection circuits. I have also seen a blown trace back there in the past.
Good luck
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Old 28th November 2006, 08:29 PM   #10
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Default SOUNDS GOOD

Joma i will check that aswell. thanks for the heads up.
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