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Old 9th January 2011, 04:00 PM   #1
Dr Zeus is offline Dr Zeus  United States
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Default JL Audio 1000/1

I got this amp in for repair, and after loking at it for while I decided to give it a shot and fix it. The amp powers up but the output terminals have a +-15v triangular wave on them. After about 10 seconds of being powered on the resistor area near the two yellow transformers started smoking.

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This area close to the output terminals appears to have damaged about 4 resistors. 3 large blue reisstors (one disintegrated completely) and one smaller white 5ohm resistor.

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I measured all the majority of the TO-220 transistors and they seem to be OK. Then I found Q511 to be measuring in-appropriatly between legs 1-2 (measuring 25 Ohms). Unfortunately I defaced some of the numbers with the tool shown and all I can make out is 111, then F0348AD. There doesnt seem to be any other transistors on the board to match this one so Im not sure what it is.

I'm also not sure of the values for all the large resistors; The one that looks like a hamburger is measuring 79k, and the one above it is measuring 21M ohms. The one that looks like a burnt marshmellow is measuring 5Ohms but one of it's legs broke and needs replacing.

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Old 9th January 2011, 04:24 PM   #2
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Q511 is likely a J111. It's likely OK. This is covered on the 'Checking Semiconductors' page, item #6.

The resistors in front of the inductors are 5 ohms.

Clean the soot off of the inductors. Is there any signs of overheating?
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Old 9th January 2011, 04:49 PM   #3
Dr Zeus is offline Dr Zeus  United States
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I just read that about Junction transsitors about a week ago too... I'll put the J111 back in.

The two inducors which somewhat survived both have slight bulging and signs of melting but it may have been from C514's demise which was the one which disintegrated. The one which is marked 106k100 is measuring 22M Ohms, and the one marked 685J160 is measuring 80k Ohms.

C514 disintegrated
C515 is marked 106K100
C516 is marked 686J160

Last edited by Dr Zeus; 9th January 2011 at 05:03 PM.
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Old 9th January 2011, 04:59 PM   #4
Dr Zeus is offline Dr Zeus  United States
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Also, the amp's top cover has a few signs of spots which probably didnt short; but may have been areas subjected to soot from overheating. The area on the bottom right of this photo is where the bass boost control sits over.

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Old 9th January 2011, 06:09 PM   #5
Dr Zeus is offline Dr Zeus  United States
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I cleaned up the PCB a bit and the amp looks better to work with now. With the inducers and resistor removed, the amp powers and is steady with about an 8A draw. The outputs on the scope are a +-60vAC sin wave. The amp seems to be stable enough for me to test things while powered on at this point.

The 2068 opAmps are getting +-13vDC

Last edited by Dr Zeus; 9th January 2011 at 06:24 PM.
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Old 9th January 2011, 11:59 PM   #6
Dr Zeus is offline Dr Zeus  United States
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I cant quite figure this amp out. It sems to be very complex in it's design. Reading through information on a JL 500/1, Im trying to troubleshoot through the 10 pin terminal on the plug-in board.

Pin 1: 0 (Ground)
Pin 2: -13.8
Pin 3: 12.3
Pin 4: 11.04
Pin 5: 0.289
Pin 6: 13.15
Pin 7: ~0.728
Pin 8: ~0.420
Pin 9: 12.97
Pin 10: 0 (Ground)
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Old 10th January 2011, 12:07 AM   #7
Dr Zeus is offline Dr Zeus  United States
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The voltages onthe back of the power supply board match up what they should be.
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Old 10th January 2011, 12:23 AM   #8
Dr Zeus is offline Dr Zeus  United States
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Pin 7 of the small yellow transformer does not appear to be what it should. Its a waveform exactly like Pin 6 when it should be -0-.

Also Pin 4 looks like Pin 2, and Pin 5 has -0- on it at all but should look like Pin 4 is not.
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Old 10th January 2011, 07:36 AM   #9
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Have you replaced all of the burned parts?

You can't expect it to work properly with all of those parts missing.
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Old 10th January 2011, 12:34 PM   #10
Dr Zeus is offline Dr Zeus  United States
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OK I'll follow up after I replace the parts. Thanks
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