JL Audio 500/1 v1 Rev. 10 Board - diyAudio
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Old 20th August 2011, 11:12 PM   #1
RiLoWa is online now RiLoWa  United States
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Default JL Audio 500/1 v1 Rev. 10 Board

This amp is not passing audio. When I received it, the inputs were missing the insulators and were tightened down to the metal case grounding them out. Here is what I have on the 10 Pin connector with 14V on the B+.

1: 4.99V
2: -14.74V
3: 14.02V
4: 2.358V
5: 13.31V
6: 13.46V
7: .636V
8: 13.24V
9: 13.31V
10: 10.7mV

What do I check next?
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Old 21st August 2011, 12:39 AM   #2
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Can you find audio on any of the output pins of any of the op-amps on the preamp board?

Have you tried lifting then re-seating the preamp board a few times?

Have you tried operating all switches and pots through their entire range with signal and a speaker to see if audio ever played through?
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Old 21st August 2011, 01:48 AM   #3
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I find audio on the outputs of U1 and U3 only.

Yes & Yes to the next two questions with no improvement.
Currently low pass is off, subsonic is off and bass EQ section is off.
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Old 21st August 2011, 02:02 AM   #4
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What rev is the preamp board?

Recheck pin 4 on the 10 pin connector. It's lower than it should be.

If it's still reading less than 5v, measure the DC voltage across the points in the attached image.
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Old 21st August 2011, 02:47 AM   #5
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Preamp board is Revision 10.

Pin 4: 2.372V

If that is U400 in the lower left then I have 2.351V across those points.
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Old 21st August 2011, 02:50 AM   #6
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That's a 5.6v Zener if it's marked 5.6. It's used as a reference for some of the logic circuits so it needs to be close to its rated voltage.

What is the DC voltage on all of corner pins of U400?
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Old 21st August 2011, 02:55 AM   #7
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Yes it is marked just like your photo.

U400
Pin 1: .925V
Pin 7: 12.15V
Pin 8: 12.21V
Pin 14: .921V
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Old 21st August 2011, 03:01 AM   #8
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Those look OK so it may not be causing a problem but I'd suggest replacing it.

Does the amp produce absolutely no audio or does it produce a very low level output?

What is the DC voltage on the positive and negative speaker terminals (black probe on the amp ground)?

Do you have 15v on the power supply pins of the op-amps just behind the input RCAs?
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Old 21st August 2011, 03:01 AM   #9
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I have another Rev. 10 preamp board BUT it is in another amp that needs it's output and power supply FETs replaced so it isn't known working. If you think we can introduce that variable, I can try it.
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Old 21st August 2011, 03:02 AM   #10
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Check the items in post #8 first.
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