Hey guys got this amp for free because it obviously doesn't work. I opened it up and from what I can see is it has a blown power supply. All 8 IRFZ44N's and blown and so are the gate resistors. Now I'm not to familiar with these amp as I always worked on Rockford amps a lot. Where can I start on this JL to get it working again? What do I check? And what's the value for the gate resistors? Thanks guys and any help appreciated.
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he gate resistors are 47 ohms. When you install the new ones, do so with the body of the resistor about 1/8" off of the board so they don't burn the board if they fail again.
Check the output transistors.
Use IRF3205s as replacements in the PS.
The driver transistors sometimes fail. If you have a scope, check the drive signal before installing the FETs.
Check the output transistors.
Use IRF3205s as replacements in the PS.
The driver transistors sometimes fail. If you have a scope, check the drive signal before installing the FETs.
What's the size of these resistors? So I can order them. And by checking the drive signal would it be the same as if I checking on a RF amp? Black probe on neg and red probe on the gate pad?
I checked the four IRF540's and they measure at 0.486 on all four.
And when I replace all gate resistors can I install 4 fets to test if it'll power on? I'll be using my 6 amp 13.8 power supply.
The resistors can be 1/6 watt or 1/8w.
Why not install all of the FETs at once?
Make sure that you bend the legs on the new FETs like the originals. If you do not, they may not lay flat against the heatsink and could fail prematurely.
Why not install all of the FETs at once?
Make sure that you bend the legs on the new FETs like the originals. If you do not, they may not lay flat against the heatsink and could fail prematurely.
Ok I installed new power supply fets and gate resistors. I used IRF3205 with the 47 ohm resistors. The problem is the fets start to get hot as soon as I apply remote. Could it be R504 is missing? The outputs don't appear to be shorted.
Possibly. Pull all of the outputs, clean the solder from the pads and power up the amp. Does it power up and draw only about 1 amp?
I installed a 470 new smd resistor problem went away no more hot mosfets not even the outputs get warm. I put it back together and tested for audio it seems to play. I'm using my iPhone as a source to play music but when I touch my phone it makes a buzzing sound not like a high pitched sound like when you touch the rcas it makes that buz sound. But it still plays.
I have another problem with this amp now. The problem is it cuts out when I turn it past above 50% volume. As I was testing it with a 4 ohm sub woofer for about an hour. Could it be the four 540's are leaky or one is leaky? Doesn't pull excessive current or have any dc offset at the terminals.
These amps are very sensitive to low voltage or dips in the voltage. Unless it was cutting out in a vehicle with a well charged battery and proper wiring it's difficult to know if the amp has a problem.
I was running it with a car battery with a small car battery charger. It could be what you explained. But I also plugged it in my friends car did the same thing.
Yeah that's one thing I haven't experienced yet still works and plays like normal but when it's turned up it will cut off. I will test it again this time with the car running. I went over the amp after I repaired it. Clean the areas where I did work on with a little bit of acetone from any debris. I'll report back. Also these will handle 4 - 2 ohm loads? I'm using a Kicker CVX dual 4 ohm it's wired at 2 ohm.
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