But then again I'm not seeing the proper gate drive voltages. Could it be that whatever happened that burned the IC and trace has killed some other components, like the caps surrounding the IC?
I have no idea at this point. The controlled start was the last thing I knew to try.
I assume that the drive still isn't the 10v square wave that it should be. Is that true?
I assume that the drive still isn't the 10v square wave that it should be. Is that true?
The IC has UVLO which will shut it down if the voltage on those points drops too far. Initially, the voltage is supplied by resistors from the positive rail but after oscillation starts, it's supplied by the low-side VCC2 supply. It shouldn't drop (measured directly across the #25 points) very far below the voltage across the COM and VCC2 terminals.
You can but you've repeatedly posted that it's up around 14v. The rest of the voltages on the #25 points should remain up around 12v. The A-D voltages are what's important, assuming that point E is as it has been.
I pulled the cap that's across the IC pads that was burned and when tested with my T7 it measures 64uf 18% vloss and ESR is 11 ohms. When tested on my DMM it measures nothing. The dots just keep jumping.
Installed a different cap just tested it and now channel 1 sounds normal when I pulse it with my finger but channel 2 sounds distorted.
Why are you using your finger? Use music or a test tone.
Sounds? distorted? Drive a sine wave into the amp and take a photo of the distorted signal and post it.
Sounds? distorted? Drive a sine wave into the amp and take a photo of the distorted signal and post it.
It's quicker with my finger lol! A quick touch and I can tell if the there's audio.
So C44 and the one next to it and C83 have very high ESR. I've changed those caps on channels 1-2 and they sound normal playing music, I'm in the process of changing channels 3-4 but the donor board I have is all out.
So C44 and the one next to it and C83 have very high ESR. I've changed those caps on channels 1-2 and they sound normal playing music, I'm in the process of changing channels 3-4 but the donor board I have is all out.
OK but I can't work with that. If you need further help, I need photos of the clean and distorted waveforms.
It seems like those 4 caps were the issue, I changed them all out and now the amp is playing.
I can't test it yet and give a scope reading because it's still pretty early at my house.
I will send it to in a few hrs. These are some photos of what I did, I apologize about how it looks but it was the best I could do given the fact that the IC traces were ruined and I don't have anymore surface caps because the donor board is all out.
I can't test it yet and give a scope reading because it's still pretty early at my house.
I will send it to in a few hrs. These are some photos of what I did, I apologize about how it looks but it was the best I could do given the fact that the IC traces were ruined and I don't have anymore surface caps because the donor board is all out.
Attachments
If those caps weren't holding the voltage (due to low value), it could have been triggering the UVLO for the high-side after the IC tried to start oscillating.
What does one of the capacitors you used as a replacement read with your capacitance meter.
Scope on auto, again. 🙁
Scope on auto, again. 🙁
