With an open input on the op-amp, the output could be anything. With 8 and 9 bridged, the output on pin 8 should be the same as the input on pin 10.
An op-amp can't be used for audio without feedback from the output to the inverting input. If you pull 8 or 9, you break the feedback loop and the output will not be anything useful.
I don't know what you're trying to do by pulling those pins.
I don't know what you're trying to do by pulling those pins.
When I short 8 and 9 audio signal disappears. The audio signal on input 9 is not clean either. The audio on pin 1 and pin 14 are clean
I apologize for my lack of understanding. My thought process was.. if you have signal in then you should have signal on the output unless the ic was damaged.
Pin 10 is ~6vdc with no waveform. Shorting pin 8 & 9 has no affect. I don’t have a njm3403 laying around. I will have to order some if we are leaning towards the op amp being defective
Did you increase the input signal (gain and crossover at max)?
If you had signal driving the 4080, you had to have signal on pin 10.
If you had signal driving the 4080, you had to have signal on pin 10.
I only had signal on pin 9 and pin 8. I am unable to increase signal into the rca input. Crossover is at the max. If start increase the gain I can hear some high voltage arching so I have turned it up more than 1/2 way.
Arcing? See if you see anything (look at many different points) with your scope that corresponds to that sound.
Does the 12v current draw change when you hear that sound?
Does the 12v current draw change when you hear that sound?
I had to remove the current limiter to verify current draw. With the crossover all the way max and turning the gain up, the arcing sound is coming from both sides. It is hard to tell. But the current draw starts to increase with no load and is jumping with arcing sound.
Hey perry just to confirm these voltages are correct. Voltages were taken with positive lead on the center leg of the IRF3710z. I be posted a pic with voltages. Please let me know if this is correct. Voltages taken with no load and no signal input.
Attachments
I just swappes ic1 wth ic2 to see if the problem followed the njm3403. Ic2 still has the same distorted waveform on pin8 and pin 7 of the 4080.
I swapped out ic3 and my dc offset control has no effect on voltage on speaker terminals. Before if I adjusted it, the voltage would start oscillating. It is now stable but still hat 0.3vdc. With a 60hz signal and cranking the gain for approximate ~30vac on the speaker terminals I have ~12vdc. Amp is humming and maybe not arcing. I removed the large inductors and inspected them. I also continuity checked to make sure they were not arcing at high voltage.
I've never tried to measure the voltage like that. The low side FETs have leg 3 grounded. The high-side FETs have the center leg on 80v. The 3rd leg of the high-side and the center leg of the low-side have a rail-rail oscillation (0-80v).
Are you seeing that 80v r-r oscillaton?
What's the status of the pins 8-10 that were previously mentioned?
Are you seeing that 80v r-r oscillaton?
What's the status of the pins 8-10 that were previously mentioned?
