Intensity Pro - Crackly audio 1080i

This problem cropped up last year. I solved it by replacing the Intensity Pro with another one I bought off eBay.
Today it has the same problem. First thing I did was to replace it with 3 known good Intensity Pro's. Not a one of them worked without the crackly audio. Next I removed the Intensity Pro, removed all of the drivers then tried an Intensity Pro 4K with new drivers. Oh, and yes, I powered off and disconnected the power cable then drained the capacitors before each step.
The computer is isolated from the network. It's a video editing station only. That means no updates. Nothing changes.
My question is this, has anyone else experienced the same problem and was it corrected? If yes, how?
I can start out with a new OS if I have to but why if this is a known problem. Perhaps it could be thermal?
I have 4 Intensity Pro's and 1 Intensity Pro 4K. These are the best pieces of editing hardware. I'll not give up trying to make this work.
Anyone have any ideas?
Thanks,
Terry
Today it has the same problem. First thing I did was to replace it with 3 known good Intensity Pro's. Not a one of them worked without the crackly audio. Next I removed the Intensity Pro, removed all of the drivers then tried an Intensity Pro 4K with new drivers. Oh, and yes, I powered off and disconnected the power cable then drained the capacitors before each step.
The computer is isolated from the network. It's a video editing station only. That means no updates. Nothing changes.
My question is this, has anyone else experienced the same problem and was it corrected? If yes, how?
I can start out with a new OS if I have to but why if this is a known problem. Perhaps it could be thermal?
I have 4 Intensity Pro's and 1 Intensity Pro 4K. These are the best pieces of editing hardware. I'll not give up trying to make this work.
Anyone have any ideas?
Thanks,
Terry