I recorded the noise from the woofer after I had replaced both of those op amps as it is still there. Undoubtedly it was not a supported file type. I'm cakllng it a night. Thanks for all your help.
The first op amp (without a board designation, item #39) now has the following voltages:
Pin 1) .001
Pin 2) .001
Pin 3) .002
Pin 4) -15.11
Pin 5) .001
Pin 6) .0025
Pin 7) .002
Pin 8) 14.85
I get a distinctive hum when I put the positive lead from my DMM on pins 5 and 6 to check the voltage.
The op amp designated as IC6 now has the following voltages:
Pin 1) 14.45 (This voltage changed from a -13.73 to a positive voltage)
Pin 2) 1.206
Pin 3) .439
Pin 4) -15.11
Pin 5) .009
Pin 6) .011
Pin 7) .010
Pin 8) 14.85
I get a distinctive hum when I put the positive lead from my DMM on pins 5 and 6 to check the voltage on this one also.
Pin 1) .001
Pin 2) .001
Pin 3) .002
Pin 4) -15.11
Pin 5) .001
Pin 6) .0025
Pin 7) .002
Pin 8) 14.85
I get a distinctive hum when I put the positive lead from my DMM on pins 5 and 6 to check the voltage.
The op amp designated as IC6 now has the following voltages:
Pin 1) 14.45 (This voltage changed from a -13.73 to a positive voltage)
Pin 2) 1.206
Pin 3) .439
Pin 4) -15.11
Pin 5) .009
Pin 6) .011
Pin 7) .010
Pin 8) 14.85
I get a distinctive hum when I put the positive lead from my DMM on pins 5 and 6 to check the voltage on this one also.
I double checked and the voltages I posted are the readings I am getting. Not that it should make a difference, this was a TL072 and I put in a 4558 just to check. Do I need to replace it again?
It's odd that the voltage is so close to the positive supply voltage. I don't think the TL072 can drive that high. If there is nothing external driving pin 1 high, the op-amp appears to be defective.
I cut pin 1 on IC6 to remove it from the circuit. The 14.45vdc was still on the pin but not on the pad. I replaced it. In checking, I can not find any connections to pins 1, 2 or 3 on this chip. Pin 7 makes its way through a capacitor to R201 and to pin 8 of the output driver board. Pins 5 and 6 make their way back through caps and resistors to the sub-sonic potentiometer.
Did you try replacing it again?
Check the tip on your soldering iron (when it's on) to confirm that there is no AC or DC voltage present.
Check the tip on your soldering iron (when it's on) to confirm that there is no AC or DC voltage present.
I connected the ground of my dmm to the chassis of the soldering station and probed the tip. 0vdc and 0vac.
After I cut pin 1 as stated in #67 above, I replaced it. The voltages on it now are:
Pin 1) -3.50
Pin 2) 1.111
Pin 3) .417
Pin 4) -15.12
Pin 5) .000
Pin 6) .000
Pin 7) .000
Pin 8) 14.84
I do not see nor can I find any connections to pins 1, 2 or 3.
Pin 1) -3.50
Pin 2) 1.111
Pin 3) .417
Pin 4) -15.12
Pin 5) .000
Pin 6) .000
Pin 7) .000
Pin 8) 14.84
I do not see nor can I find any connections to pins 1, 2 or 3.
If you can open this, it is the static sound that comes through the woofer. This is without any input.
Do you see that noise at the input to the driver board?
What's the amplitude of that signal at the speaker terminals?
What's the amplitude of that signal at the speaker terminals?
Follow the signal path back to see where it's entering the audio.
Does the position of any switch or pot make a difference?
Does the position of any switch or pot make a difference?
I have not been able to find the source of the noise. The noise is visible on the scope at every point in the pre-amp section from the RCA inputs to the driver board.