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Old 9th January 2013, 08:59 AM   #1
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Default Rockford Fosgate Power 650

I have a Rockford Power 650 for repair.

I have 46.5 vdc on all of the output wires.

The amp does not draw current and idles fine.

Is it possible that all the outputs are shorted?
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Old 9th January 2013, 09:01 AM   #2
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Do you have both positive and negative rail voltage on the 3rd leg of the outputs for all 4 channels?

Do you have positive and negative supply voltage on all op-amps?
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Old 9th January 2013, 09:06 AM   #3
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Yes on all the FETS except for 3 there is hardly any DC.
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Old 9th January 2013, 09:22 AM   #4
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I now have positive and negative rail on leg 3 of all fets I had a blown fuse. There is full rail on all bridging wires????

The 2 op-amps in the middle of the board have no + supply the rest of the op-amps have +/- supply??
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Old 9th January 2013, 09:29 AM   #5
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Please read edit on post #4.
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Old 9th January 2013, 09:53 AM   #6
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The positive supply pin for those two op-amps goes back to the collector of an MPSA56 transistor. Follow the traces back to see where it goes. I think it's likely one of the 4 transistors in the rectangle.
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Old 9th January 2013, 10:03 AM   #7
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I did that and found the A56 defective. I replaced all four A56 and A06 and now one of the resistors in one channel is turning brown and smoking.

There is 4 of these resistors in each channel I think they are 29.1 ohm??
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Old 9th January 2013, 10:24 AM   #8
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They are 390 ohm like the one thats burned in your picture next to the bias pot.

Something is putting rail across that resistor.
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Last edited by seankane; 9th January 2013 at 10:39 AM.
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Old 9th January 2013, 10:56 AM   #9
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Read post 7 and 8 first.

I checked the other 390 ohm resistors as there are 4 in each channel. They all have rail across them why is only this one burning?
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Last edited by seankane; 9th January 2013 at 11:17 AM.
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Old 9th January 2013, 12:44 PM   #10
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Do you mean that they have 45v across them if you place one probe on each terminal of the resistor?

Did the rail voltage go away on the bridging wires?
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