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seankane 9th January 2013 07:59 AM

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?

Perry Babin 9th January 2013 08:01 AM

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?

seankane 9th January 2013 08:06 AM

Yes on all the FETS except for 3 there is hardly any DC.

seankane 9th January 2013 08:22 AM

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??

seankane 9th January 2013 08:29 AM

Please read edit on post #4.

Perry Babin 9th January 2013 08:53 AM

1 Attachment(s)
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.

seankane 9th January 2013 09:03 AM

1 Attachment(s)
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??

seankane 9th January 2013 09:24 AM

They are 390 ohm like the one thats burned in your picture next to the bias pot.

Something is putting rail across that resistor.

seankane 9th January 2013 09:56 AM

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?

Perry Babin 9th January 2013 11:44 AM

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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