If you have 10 volts on more on pin 17, the IC is defective.
What is the resistance from the pad for pin 18 and ground. Make sure you're not touching pin 18 when measuring the resistance.
What is the resistance from the pad for pin 18 and ground. Make sure you're not touching pin 18 when measuring the resistance.
I wouldn't expect to see a completely open circuit (OL) but at least it's not reading near 0 ohms.
The next step would be to replace the IC.
The next step would be to replace the IC.
That appears to be the right one. They make them in two different widths (if I'm not mistaken) but that's likely the one you need.
was bored and decided to desolder U1. then went ahead and remeasured resistance from solder pad of leg 18 to ground. was 132ohms
That would be 38ma which would exceed the maximum output from the 5v regulator. I think the LM339 that you previously replaced probably shorted internally. It's also possible that the capacitor connected between pin 18 and ground may have failed.
okay, so i should go ahead and replace the lm339 at U3, does that mean the U1 may still be good? and whats the board designation for the capacitor.
If U1 didn't have 5v on pin 18 (pin 18 off of the board) when pin 17 had 10v+, the IC is almost certainly defective.
Remove the 339 and measure the resistance from pad 18 to ground. Is it significantly more than 130 ohms?
Remove the 339 and measure the resistance from pad 18 to ground. Is it significantly more than 130 ohms?
okay i assumed when u said pin 18 you meant of U1 as U3 has 14 legs. with 339 removed pin 18(on board) to ground is 133 ohms
Remove C6. It should be very near pin 18. Does that change the reading from pad 18 to ground?
I checked a Rockford amp here with a similar circuit and it's reading greater than 1.6k ohms from pad 18 to ground.
I checked a Rockford amp here with a similar circuit and it's reading greater than 1.6k ohms from pad 18 to ground.
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