Famicom sound weird drum effect

[fredJ]

I have an AV modded famicom that adds extra beats here and there

It seems playable but it gets annoying quickly.

Any idea what it could be? I tried replacing caps C2 and C7 I think, and it sounds exactly the same.

In this video you can here at at :02 and :04
https://www.youtube.com/watch?v=fqfiOV-KtGU

Also the sound is a bit buzzing and hissing.
Post Merge: February 23, 2017, 03:50:17 am
I think it is something with the CPU that is defect, my colleague believed it.

So I won't bother trying to fix it.

[P]

Where is the extra beat in more detail? I hardly hear the beats at all.

What revision of the CPU is it?

[fredJ]

Here also, around 0:25
https://www.youtube.com/watch?v=6Y5rjRsW5Ek

It is the older model, don't know exactly, quite annoying problem, too bad I didn't notice before we modded it.

[P]

I guess it's more audible in person than in a recording. I do hear some strange sounds but I can't tell if they are part of the background noise or the game sound.
At 0:25 Mario is catching a power up so the sound effect is taking over the sound channels, so it's hard to hear anything strange at that moment.

[Skawo]

I just noticed I have this same issue.
https://www.youtube.com/watch?v=AVkuT6t_FXY

Aw man. I don't suppose you ever figured out how to fix it?

[fredJ]

It was a long time ago...
I haven't had the problem since with any console. And I think I just sold it "as is", and I haven't heard about it since...