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#1 |
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diyAudio Member
Join Date: Oct 2010
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This amp seems to be a bit of a stumper for me. I read the section on BD1500 on the DVD and am still a little confused as to what is going on with this amp.
It powers and is stable on the bench out of the sync. Rail voltage seems to be a bit confusing; either that or secondary ground has floated well beyond what I normally see, although now as I type this up I believe this amp really only produces positive rail voltate. Referencing amp's general ground, I see 112vDC at the rail and 56vDC on RCA shields. If i reference R44 which I believe is CT I see +57vDC and -55vDC at the rails, but I also see -55vDC on RCA shields. Referecing RCA shields, I measure expected voltages on the opAmps except for U4, which may be dragging the regulated voltage down to +9vDC and -10vDC. To be more clear, the other three opamps are seeing +-13.5vDC on the power pins. U4 is showing ~0 volts on remaining pins except pin 1, which has -.65vDC on it. Both sets of LM3x7 regulators seems to be running hotter than expected. There appears to be somewhat decent audio waves on several of the opamp pins but the audio path may not be reaching the outputs. |
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#2 |
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diyAudio Member
Join Date: Oct 2010
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There are actually 3 pairs of LM317/LM337 regulators on this amp. Q15/Q16 and Q1/Q3 are getting much hotter than Q13/Q14
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#3 |
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diyAudio Member
Join Date: Nov 2003
Location: Louisiana
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Measure the rail voltage across the twisted red/black wires.
Do you have audio on U4, pin 1?
__________________
Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links |
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#4 |
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diyAudio Member
Join Date: Oct 2010
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Boy, these rockford amps are quite different than their Class-AB counterparts. The LED on the side near the RCA shields indicates protection, and it is illuminated when the amp is powered.
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#5 | |
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diyAudio Member
Join Date: Oct 2010
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Quote:
Yes, U4 has audio on pin #1 |
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#6 |
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diyAudio Member
Join Date: Nov 2003
Location: Louisiana
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Voltage on all 8 pins of U17?
Pin 1: Pin 2: Pin 3: Pin 4: Pin 5: Pin 6: Pin 7: Pin 8:
__________________
Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links |
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#7 |
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diyAudio Member
Join Date: Oct 2010
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U17 is an LM6171
Pin 1: 0.003 Pin 2: 0.052 Pin 3: 0.050 Pin 4: -9.40 Pin 5: 0.001 Pin 6: -1.237 Pin 7: 9.76 Pin 8: 0.010 |
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#8 |
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diyAudio Member
Join Date: Nov 2003
Location: Louisiana
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It appears to be OK. What is the DC voltage on pin 2 of U5 and U8?
What's the DC voltage on pin 6 and pin 7 of U21?
__________________
Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links |
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#9 |
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diyAudio Member
Join Date: Oct 2010
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U5 and U8
Pin 2: 6.42 U21 Pin 6: -8.67 Pin 7: 8.45 |
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#10 |
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diyAudio Member
Join Date: Nov 2003
Location: Louisiana
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U21 is defective. The amp is in protect mode. The protection LED should be lit.
__________________
Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links |
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