amp stopped working (jl 600/1v2)

[4x4audio]

Hello, I hope it's ok to make a new post as the others are rather old.

My amp stopped working. I wonder if anyone can please clue me in with what's wrong with it.

The amp powers up flashing the green led then turns solid green but there is very little to no output.

There is no burnt smell nor can I see anything burnt.

I measured the pos/neg speaker output while powered up on a bench with no signal input and it measures .04v each.

When I measured power ground with the speaker terminals it registered 26.64v across all speaker terminals positive or negative with no signal input.

Amp does not go into protection mode as far as LED indicators show.

The only thing I noticed at the time was my positive power wire was loose at the battery and may have had a loose ground as well.

ANL fuse did not blow at the battery.

Thanks for your help.

 

[Perry Babin]

Have you tried operating all potentiometers and switches through their entire range to see if the amp ever produced any sound?

 

[4x4audio]

Hey thanks for replying.

If the amp ever? It was working fine but stopped for some reason. Yes, I have moved the switches and the input level potentiometer. Do the voltages at the speaker output look normal?

 

[Perry Babin]

The question was, did the amp ever produce any audio/noise when moving the pots and switches?

I don't know this amp (never had to repair one) but it's common for JL amps to have 1/2 of rail voltage on all of the speaker terminals.

 

[4x4audio]

I didn't hear anything but being a subwoofer maybe it's hard to hear anything like that when it's in a sealed band pass box.

I thought maybe the voltages may have some indication of what may or may not be wrong.

 

[Perry Babin]

Have you tried the amp with another speaker?

If you don't have another speaker, connect your multimeter across the positive and negative speaker terminals (AC volts) and see if the meter indicates that there is voltage present when a signal is driven into the amp.

 

[4x4audio]

Well, I tried a different amp and that works. I need to find a small radio or some source so I can check that rather than put it back into the car.

So 26.64v across all the speaker terminals while using the negative probe at the power ground is not a useful measurement? I don't know why there is more than 12 volts there so it doesn't really say anything to me other then the amp is getting power.

 

[4x4audio]

Whenever I get the chance, i've been reading your website. It's very interesting. There's a lot to soak up! I'll have to read through it twice to understand and retain as much as possible. Thanks for putting it out there.

 

[Perry Babin]

For standard (class AB, class B...) amps, DC voltage (with respect to the primary ground) will generally be very near 0v DC. For high-power head units and some class D amps, DC on the speaker terminals is normal. The JL 500/1 typically has 40v DC on the speaker terminals.

 

[4x4audio]

For standard (class AB, class B...) amps, DC voltage (with respect to the primary ground) will generally be very near 0v DC. For high-power head units and some class D amps, DC on the speaker terminals is normal. The JL 500/1 typically has 40v DC on the speaker terminals.

Being that this amp is the 600/1 with only 26.64v across all the speaker terminals, would that indicate that there is a problem in this circuit?

 

[4x4audio]

I just hooked up from my laptop headphone jack to the amp, running on a small 12v battery, with the volume turned all the way up and the amp gain all the way up - i'm seeing 1-25v AC at the output terminal (with no speaker load though) . So it's not blown?

 

[Perry Babin]

I have never had to work on one of these so I have no definitive information. The only thing I could tell you is that having significant DC on all speaker terminals isn't out of the ordinary for JL class D amps.

Some JL amps will produce low level audio if the low voltage (driver and preamp) power supply is functioning but the main supply is blown.

Is the 1-25 a typo or did you see up to 25v AC when the probes were connected to the positive and negative speaker terminals?

 

[4x4audio]

Well, I was playing music rather than a test tone so the voltage was wildly fluctuating, peaking around 25v AC. The probes were not attached to any speaker terminals, just the amplifier's outputs. Also, this battery is low at 11.53v and I was using speaker wire for power (only a couple of feet though).

 

[4x4audio]

***edit -
so I put it back in the car and i'm not so lucky. It reads zero volts now.....strange.

 

[Perry Babin]

Do you read approximately 12v on the B+ and remote terminals with the black probe on the ground terminal of the amp?

 

[4x4audio]

I uninstalled it out of the car so I will need to put it back temporarily. I will say that the amp turns on normally (blinking green then solid green) and the other amp taking it's place, for now, works with no problems. (using the same wires)