JL AUDIO E6450

[mike49504]

I got this amp in for repair. The amp had 2 blown outputs so i removed them .
I still have problems with that channel since the new outputs got red hot .

The other problem is the amp is producing both + - regulated and rail voltages but i have no output out of any of the channels.

Any ideas on where to look?

 

[mike49504]

Ok i checked again . ALL of the outputs get hot within secs

 

[807tubenut]

did you check the output drivers?

 

[Perry Babin]

Biasing?

Gate resistors?

 

[mike49504]

i removed 4 bad outputs from this amp the other 8 are still in it.

All 8 get red hot within secs . The 4 i removed where bad the other outputs that are still in the amp tested fine.

Do i need to turn all of the bias pots down in every channel?

Also when i connect a sub to any channel i get fluttering on the outputs .

I tested for DC on the outputs but theres none.

 

[Perry Babin]

Turn all 4 channels down but before you do, measure the bias voltage across the test points to see what the factory bias is.

Do you get fluttering with no RCAs plugged in?

 

[mike49504]

Well i figured out the fluttering problem.

Wheres the test points for the bias on this amp?

 

[Perry Babin]

Near the white source resistors.

What was the fluttering caused by?

 

[mike49504]

When i plugged in the RCA's i didnt notice it at first but i had the rca's plugged into my sine wave generator not the test deck

 

[mike49504]

Ok are you talking the diodes for the test point or is there anyway you can put arrows in the pic thats in the previous post?

 

[Perry Babin]

See attached

 

[807tubenut]

Yep, that's them, I recently went through my 4 and 6 channel JL amps, factory bias on the 4 channel was 6mv DC, and the 4 was 5mv DC, I have tested @ 2-4-6-8-10mv, Amp runs cooler/better around 4~6mv DC

 

[mike49504]

Ok that took car of the outputs heating up.

Now i have to troubleshoot 5 out of the 6 channels.

1 channel plays perfectly.

3 channels have very low output.

and the other 2 channels were the ones with blown outputs.

 

[Perry Babin]

Do you have approximately negative 15v on all of the J111 transistors (Qx01?, leg 3)?

 

[mike49504]

yes

 

[Perry Babin]

Remove the muting transistors from the weak channels to see if the audio level returns to normal.

I'm assuming that you've run all of the controls on the front of the amp through their entire range...

 

[mike49504]

will the 540N's work in this amp or not?

 

[Perry Babin]

I don't know. Try them in one channel to see if they cause problems (like they do in some Rockford amps).