JL Audio 1000/1

[S Merlington]

I'll see if I have one if not I'll order it and post back

 

[S Merlington]

Would the 293 work for U800 ?

There is a LM393 in that location now but it looks like its been replaced before

 

[luigidedom]

hi hope these help

 

[S Merlington]

Thank you for the pics greatly appericated..

 

[S Merlington]

Perry,

I replaced U800 with a LM293 ..

Original was LM393

I check the resistors in that general area and they test good..

Anything else i should check before power the amp back up to see if anything has changed?

 

[S Merlington]

Ok i powerd the amp back up..

Heres what i get on U800 after replacing it

Pin 1:4.93
Pin 2:0.00
Pin 3:0.80
Pin 4:0.00
Pin 5:4.91
Pin 6:0.40
Pin 7:0.00
Pin 8:12.53

So there is no change in the voltages on Pins 5and 7 after replaing it

 

[Perry Babin]

With no power applied, what resistance do you read between pin 7 and pin 4 of U800?

 

[S Merlington]

3.277K ohms

 

[Perry Babin]

I think R848 connects between 5v and U800, pin 7. Confirm that you read 0 ohms to pin 7 and 5v on the other end of that resistor when the amp is powered up.

 

[S Merlington]

If R848 is a 3.3K resistor pin 7 connects to it..

From Pin 7 to R848 i get 0.02 ohms

On the other side of that resistor i dont not get 5 volts it remains at 0.00 volts whn trying to power the amp up the voltage never moves from 0.00

Pin 7 also connects to a 9.1K resistor and i get 0.02 ohms to pin 7 also..

The other side of that resistor the voltage remains at 0.00 volts and never changes..

The 9.1 K resistor connects to pin 8 of U801 (MM74HC02M)

Pin 8 remains at 0.00 volts..

I noticed the on that IC the pads on Pins 3 and 4 are missing off the board but all other pads are intact..

Pins 3 and 4 of that IC (U801) do not connect together do they?

 

[S Merlington]

It's connects to pin. 14 of u 801 not pin 8

See post above

 

[Perry Babin]

I think that all of the logic ICs (74....) operate off of 5v and for all of them, the top left pin is 5, the bottom right pin is ground.

I think all of the pins on U801 are used.

Follow the traces back for the 5v power. Virtually every power source in these amps passes through a 10 ohm resistor before going to the IC. The resistors sometimes open.

 

[S Merlington]

I checked all of the 10 ohm resistors all measure fine..

I checked to see if i had any open traces and or junctions all are fine..

But im not getting the 5 volts on the IC's


Any ideas on where i go from here??

Also do you or anyone have a high res pic of U801 ?

 

[Perry Babin]

http://www.bcae1.com/temp/IMG_6357.JPG

This is the best I have. Click to view full size.