Hello,
I'm new to this forum. After a solid hour reading Perry Babin's page on beginner amp troubleshooting I am in need of assistance to an issue I have. I recently picked up a used JL 300/4 amplifier and installed it in my car. The past couple of days it has been running and sounding great. One day, all of a sudden I get massive speaker distortion through my speakers (this however is intermittent). I check the amp and sure enough the red thermal protect light is on. My immediate thought is wow the amplifier is that hot? Sure enough I touch it and its barely luke warm. I double check all my connections, tighten them down and measure a steady 12.6v with the engine off across the amp terminals. I noticed as I was measuring the terminals with a DMM if I wiggled the ground and battery + wires the thermal light would go on and off. Again I tightened and checked the connection but I think something inside the amp is loose. I opened up the back of the amplifier and to my untrained eye, everything seems to be intact and nothing is burnt or broken. Where should I start next? I appreciate all of your responses.
I'm new to this forum. After a solid hour reading Perry Babin's page on beginner amp troubleshooting I am in need of assistance to an issue I have. I recently picked up a used JL 300/4 amplifier and installed it in my car. The past couple of days it has been running and sounding great. One day, all of a sudden I get massive speaker distortion through my speakers (this however is intermittent). I check the amp and sure enough the red thermal protect light is on. My immediate thought is wow the amplifier is that hot? Sure enough I touch it and its barely luke warm. I double check all my connections, tighten them down and measure a steady 12.6v with the engine off across the amp terminals. I noticed as I was measuring the terminals with a DMM if I wiggled the ground and battery + wires the thermal light would go on and off. Again I tightened and checked the connection but I think something inside the amp is loose. I opened up the back of the amplifier and to my untrained eye, everything seems to be intact and nothing is burnt or broken. Where should I start next? I appreciate all of your responses.
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Hi Perry, I followed what you said and my results are the same. However, I managed to narrow the issue down to only one side of the board. It appears when I wiggle the side opposite the ground/battery + terminals there is no effect on the thermal light. When I wiggle the PCB both main and preamp section beside the ground/battery + terminals the thermal light goes on and off.
On a side note I noticed part of the PCB is touching one of the capacitors. I am not sure if this would pose a problem. See attached photo
On a side note I noticed part of the PCB is touching one of the capacitors. I am not sure if this would pose a problem. See attached photo
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The PCB touching the cap isn't an issue.
Is there any sign of melted plastic around the terminals where the wire goes into the terminal?
Is there any sign of melted plastic around the terminals where the wire goes into the terminal?
Nope, I took off the plastic housing and it's melt free. No signs of burning around where it protects the terminals either.
I did but left the FETs connected to the black fins part of the heatsink with their thermal paste. I separated the preamp board and there is nothing burnt on the backside of that.
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Remove the clip holding D600 and U600 to the heatsink.
Is either leg on U600 broken?
What is the DC voltage across U600 (amp on)?
Is either leg on U600 broken?
What is the DC voltage across U600 (amp on)?