JL Audio 300/4

[Hexhclass]

Amp had no output,Rail and Regulated voltages look ok.The two back driver boards have some LEDs that are not lit .

Any suggestions

 

[Perry Babin]

Desolder (important) than resolder the large 47k resistors. They can also have plating for the contacts delaminate and break free (which requires that they be replaced).

 

[Hexhclass]

I desolder and desolder them but no change.Test them in circuit and reading look good.

 

[Perry Babin]

What's the DC voltage across all of the LEDs that are unlit?

 

[Hexhclass]

Left board
.260
.425

Right board
.135
.060

I think the LED on the right board faulty

 

[Perry Babin]

Are the two resistors for those LEDs heating up?

Aren't the lit LEDs at about 1.2v?

 

[Hexhclass]

Lit LEDs 1.8v

Resistors not heating up
The driver board to the back left the LEDs try to lit when I power the amp up.

 

[Perry Babin]

DCV across the cold 47k resistors?

 

[Hexhclass]

Left board
29.15v
29.93v

Right board
83.5
45.5v

 

[Perry Babin]

There will be a single voltage for each resistor.

 

[Hexhclass]

Are you saying the voltage across all should be 80v because that’s what I see on the working board.

I will have to pull the driver board so I could check it better.

 

[Perry Babin]

No heating means that no current is flowing through it. The LEDs don't seem to have significant voltage across them so they don't seem open. The other LED is lit so it appears that the two 10 ohm resistors near the header are OK. I'm just looking for something that would point to the reason that the resistors are not passing current.