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Old 26th October 2013, 02:12 PM   #1
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Default rockford fosgate 1501bd

Perry
I have a bd1501 that I thought I had finish repairing. I had output the rail switchers and audio were switching properly. So i removed the pot from u17 and reattached r31 &35. I powered up tha amp and notice it was drawing around 5 amps. I checked and made sure outputs weren't getting hot and proceeded with checking the output with a 60hz signal. Amplifier produced clean output. I switched the 0/180 button and poof there went the rail switchers and 24.9 ohm resistors. Now that I have repaired it again I am at the same problem. I am going to replace u3 &u4 and see if it fix the problem. Any ideas....
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Old 26th October 2013, 03:09 PM   #2
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When you power it up again, make sure that the output on U17 (no input signal) is essentially a straight line on the scope. If you see excessive oscillation or noise on that pin shut the amp down and re-check the connections on the resistors and the IC.
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Old 26th October 2013, 04:39 PM   #3
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Before I tried that I un hooked r35, powered it up same thing. Okay It has a few random spikes but other than that the output is steaight. Even when the r31 and 35 out of the circuit it is around 3 to 4 amps. Seems like when it is forced to - or + voltage manually it has less current draw.
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Old 26th October 2013, 04:48 PM   #4
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3.2amps idle
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Old 26th October 2013, 05:05 PM   #5
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3.37amps at idle. Amp is out of the heatsink. Let amp stayed powered to watch current draw. Noticed the audio outputs are starting to get warm but rail switchers are not. When I got the amp the rail switchers and powersupply fets were toast. I have replaced the audio outputs, u8, or u9.
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Old 26th October 2013, 05:45 PM   #6
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Okay fets went pop again......uhggggg. amp plays perfectly fine on rockford 12" 4 ohm sub. I can give it up to 52 amps on powersupply. It blows the rail switchers like a firecracker when you flip the 0/180 phase switch.. hmmmm any thoughts. I have definitely perfected the art of popping FETS this week. Haha
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Old 26th October 2013, 09:01 PM   #7
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These amps are sensitive to high frequency input to the class D section. It's likely that the 0/180 switch has dirty contacts and is driving a signal that would sound sort of 'scratchy'. After removing the defective FETs, look at the signal on the output pin of U4 to see if you see a noisy signal when you move the switch. If you do, clean the switch to see if you can get it to switch properly. If you cannot, replace it. For testing, you could solder a jumper in place of the switch to confirm that the amp is otherwise working properly.
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Old 26th October 2013, 10:02 PM   #8
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Okay I will try that I already replaced u4 & u3 before I blew the fets. This is the pro series bd1501. I did think the 3.7 amps at idle was high. Giving it one more chance out opto couplers running low on parts.. expensive learning curve huh...I blew the fets last time I switched that switch. This time atleast it didn't take the 24.9 ohm resistors with them. Its pretty instantaneous on the. Fets blowi g when you switch the phase 0/180
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Old 27th October 2013, 03:37 PM   #9
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Perry I replaced the switch and fets this morning and the ic driver. Powerd unit up and idle current was around 3.2 amps. I also replaced both voltage regulators closest to the switches. Had nice audio output. Disconnected speaker and audio input. Flipped subsonic filter switch and rail switchers go boom. Any ideas
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Old 27th October 2013, 05:37 PM   #10
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Do you have any significant DC on any of the op-amps?
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