mikeycivic

I have a older jl 500/1 that decided not to work. No power light and sub wont come on. I swapped in a known good power feed and nothing happened. Jl can fix it for $180 which isnt really what Im looking to spend. Can anyone help me out???

nsxxtreme

JL amps I usually toss in the garbage. They are more trouble then they are worth.

What are the symptoms and are you capable of diagnosing and doing the repair yourself if you had help?
f the answer is no then take it somewhere to get repaired.

mikeycivic

it has no power is the symptom and yes i probably could

nsxxtreme

Can you open it and snap a photo of the main board?

mikeycivic

i certainly can thanks for your help check back in a bit Ill have a pic for you

mikeycivic

nsxxtreme

The lower left side of that amplifier is the power supply.
The first 8 Transistors from left to right are the supply transitors.
You will also see some small sot23 transistors near the larger supply transitors. These supply the switching to the larger transistors.

What I would do is check the smaller transistors to see if they are switching. You can use a dmm that is capable of measure AC that also displays frequency. These will feed the "gate" of the larger transistors. If these are dead then they need to be replaced.

The next thing would be to check the output of the larger transistors reaches 30V. If one is dead then it will prevent the others from working as well. You have to read it carefully because if the problem is somewhere besides the power supply then the output will reach 30V and then the protection circuit will shut the supply off.

Most amplifiers failures occur in the power supply. But JL amps aren't most amplifiers and fail just about everywhere. IMO they are throw away amplifiers. If its not the supply it would be to technically challenging to assist through the internet how to repair that amp.

Good luck!

mikeycivic

ill let you know, thanks

nsxxtreme

I have to make one correction because when I speak everything makes sense in my head and I don't always realize that someone might not be able to follow.

Do you see that large colorful inductor all the way to the left? The inductor to the right is just a filter. But the colorful one is where the magic happens. What those large transistors will do is allow current to flow on/off through one set of windings on that inductor, since the flux rotates around that ring. The current is then induced into the second set of windings. You can read further on the internet if your interested in the pysics behind it. But anyway those transistors will just switch 12V at about 100KHz if I remember correctly (not sure on the frequency really isn't that important). If you had an oscillscope you would see a square wave with a magnitude of 12-14.4V. The output of the second winding for a 500W amp would be closer to 25V I believe.

There is a PWM IC that feeds those sot23 transistors because it doesn't have enough current to feed the larger transistors directly. The output of the pwm is 98% of the time perfectly fine. Most problems occur beteen the path from the IC to the output of those supply transistors. Either those sot23 transistors die or one of the supply transistors die and take the rest of them with it.

mikeycivic

when you say check it, what exactly am I to do?

nsxxtreme

Measure the gate, drain, source of the sot23 and supply transistors. Using a dmm set to AC. Should read some x voltage at y frequency. What is x and y for each part? You should have 3 measurements for each part.

mikeycivic

umm ok lol

nsxxtreme

You can google sot23 if you dont know what gate, drain, source is. The other transistors will be similiar. If that is to complicated for you then you should take it to someone qualified to repair it.

mikeycivic

okie im sure i can figure it out, ill update ya