JL 300/4 Amp repair.

[DcMaN]

I have a JL 300/4 that JL actually repaired a few years ago because of the same issue but now its happened again, and absolutely refuse to give them another $150 for them to repair it when i am completely capable of doing the repairs my self. My problem is that i dont have enough knowledge of the components inside the amplifier to troubleshoot it so this is where i need some advice. The amp turns on, powers on fine it does not go into protect mode. I get no output on any channels, its not a wiring issue, i already replaced the amp with a jl 300/4 v2 and everything in the car is working fine. It started by the driver side speakers would hiss and pop every time i turned the amp on, then proceed to play music, however now there is no output on the amp at all in any of the 4 channels. Can anyone help me trouble shoot this amp and tell me what needs to be replaced in order to get this to work again?

Thanks

-Rob

[Perry Babin]

Do you have both positive and negative rail voltage on the output transistors?

Do you have both positive and negative regulated 15v on all of the audio op-amps?

[DcMaN]

I havnt really looked at it yet but plan on doing so when i get home from work. I am not really familiar with any of the components inside the amplifier. so i dont know the location of where these would be so i can test them. Does the no audio output symptom happen often with these amps ?

[Perry Babin]

If you're not familiar with amp internals, you should read the basic amp repair page (link below). Without that basic knowledge, it's going to make it much more difficult to get it repaired.

[DcMaN]

Thanks perry, i actually just went ahead and ordered the "Full version" of the site because i have about 5-6 amps to repair. I will get back to you shortly, but in the meantime are there anyother things i can check on the jl audio amp ?

[Perry Babin]

That doesn't contain any repair information that's not available online. The repair tutorial (if that's what you were looking for) is entirely different.

You need to understand the basics before you can do any troubleshooting. Read that page I suggested.

[DcMaN]

ok, so ive finally gone in depth about understanding alot of the compononents inside of the amplifier. I ended up calling jl audio and asking them what they actually did to repair the amplifier previously in 2006. They told me they replaced some "devices" in the auxillary power supply. Do you think that its possible the same exact devices failed in the aux power supply ? I only ask because it does have the exact symptoms that it did when it broke for the first time.

Thanks

-Rob

[Perry Babin]

Do you have both positive and negative regulated 15v on all of the audio op-amps?

[DcMaN]

Ok, so i finally got around to see what was going on with this amp. The front left channel is the only channel that will produce an output. What should i be checking for ?

[DcMaN]

Also noticed that all the driver boards except the Front Left Channel Driver board is generating a pretty decent amount of heat. Not sure if that is relevant or not.