Jl Audio 500/1v2 No audio.

[rhempz01]

Im having an issue with audio on this amplifier. Missing the negative voltage on the op amps. Power supply is up and running and the outputs are ok. It was missing R547 when I received it, and had alot of terrible sodering work. I managed to get the power supply back working and installed a 5watt 10ohm in r547 for testing, I ordered the correct resistors. I could use some help, I don't have a good understanding of these amplifiers.

 

[rhempz01]

Without preamp board

 

[rhempz01]

Amp

 

[Perry Babin]

What DC voltage do you have on the three large 4.7 ohm resistors neat T601?

 

[rhempz01]

81.5vdc
.623vdc
.595vdc

 

[Perry Babin]

That looks like you're missing both positive and negative regulated voltage. Is that what you found on the op-amps?

 

[rhempz01]

Yes I had 5vdc and then -.589

 

[Perry Babin]

I don't think the the low voltage supply is operating. Do you see a square wave on the drain of the FET standing near T601?

 

[rhempz01]

No I do not.

 

[Perry Babin]

Is the 33 ohm resistor near that transistor within tolerance?

The 0.1 ohm needs to be checked as well.

 

[rhempz01]

32.8ohm
.4 ohm

 

[Perry Babin]

Do you have 12v on the drain of that FET?

Do you see any sort of drive signal on the gate of that FET?

 

[rhempz01]

12.9vdc on drain and no drive on the gate, just .502vdc

 

[Perry Babin]

Post the DC voltage on the pins of the 10 pin header using the numbering shown below.

 

[rhempz01]

1) 5.004v
2) .045v
3) 12.94v
4) 5.96v
5) 12.93v
6) 11.95v
7) 0.00v
8) 11.73v
9) 11.55v
10) 0.00v

 

[Perry Babin]

Other than 2 and 7, those look OK. I think 2 is just for the power LED. 7 is the -15v for muting but that won't be there if the low-voltage supply isn't working.

Is the power LED lit?

It looked like the main supply was operating since it had 80v. Is the main supply operating?

 

[rhempz01]

Yes power led is lit green, and the main supply is running.

 

[Perry Babin]

What is the DC voltage on all 3 legs of the 5v regulator (U601)?

 

[rhempz01]

Leg 1 12v
Center 0.0v
Leg 3 5.02vdc

 

[Perry Babin]

What's the DC voltage on the resistor terminal highlighted below?