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.
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.
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.
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.
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.
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
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
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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
The 2068 opAmps are getting +-13vDC
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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)
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)
I've got limited space and size to get the caps replaced. The closest thing I can find to a 106k100 (10uf 100v) in the same lead spacing and size is a 15uf 100v from Digi with part number 495-4103-ND. I need to replace both in the amp so would the 15uf be a problem? I tried finding 10uf in the right size even with a different voltage rating and there is nothing.
Is the 5 ohm resistor rated at 10w?
The inductor is another one i cannot find. I need it to be LxWxH, 30mm x 10mm x 20mm, with 27mm lead spacing. Im not sure what the value is of it; marked 685J160
Is the 5 ohm resistor rated at 10w?
The inductor is another one i cannot find. I need it to be LxWxH, 30mm x 10mm x 20mm, with 27mm lead spacing. Im not sure what the value is of it; marked 685J160
Im not precisly sure what goes in all three of these locations.
I know a 10uF 100V cap goes into C515; but I only found Part Number 495-4103-ND at Digi which is a 15uF cap that will fit. Nothing else comes close with the same lead spacing.
Does the same go into C514? I dont know what came out because it looks like an over-burned marshmellow.
C516 had a 685J160 which looks and measures like a capacitor. I cant seem to figure out what this piece is though.
Can I just put 3x 15uF 100V caps into these spots?
I know a 10uF 100V cap goes into C515; but I only found Part Number 495-4103-ND at Digi which is a 15uF cap that will fit. Nothing else comes close with the same lead spacing.
Does the same go into C514? I dont know what came out because it looks like an over-burned marshmellow.
C516 had a 685J160 which looks and measures like a capacitor. I cant seem to figure out what this piece is though.
Can I just put 3x 15uF 100V caps into these spots?
Digi-Key - EF2106-ND (Manufacturer - ECQ-E2106KF)
If you can't find caps to fit, you can use these caps (for the 106K...). Bend the leads as shown and goop them to the board. Digikey doesn't have the 6.8uf in this series but maybe you can find it in a different series.
If you can't find caps to fit, you can use these caps (for the 106K...). Bend the leads as shown and goop them to the board. Digikey doesn't have the 6.8uf in this series but maybe you can find it in a different series.
Attachments
I can't think of any reason it wouldn't work. How about this:
DME2W6P8K-F Cornell Dubilier Polyester Film Capacitors
DME2W6P8K-F Cornell Dubilier Polyester Film Capacitors
After installing a new resistor and three new caps, power up is stable. Unfortunately the speaker terminal outputs are not cooperating, and the amp is constantly outputing a medium volume 60hz frequency on top of whatever my frequency generator plays.
If I flip the "output polarity" switch from 'Normal' to 'Reversed' then the amp plays nothing - no 60hz and nothing from the frequency generator.
If I flip the "output polarity" switch from 'Normal' to 'Reversed' then the amp plays nothing - no 60hz and nothing from the frequency generator.
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