Famicom audio circuit

[aha2940]

Hi!

I have a discrete famiclone which I have modified: replaced the clon CPU and PPU by original Nintendo CPU and PPU and did the jpx72 mod for cleaner video: http://jpx72.detailne.sk/modd_files/fc/avmod.htm and it worked beautifully, the video signal improved a lot.

However, the audio part of the mod suggests soldering a 220uF capacitor from the pin 46 of the cartridge connector to the audio output. I checked my famiclone and it has two resistors in series from the pin 46 to the audio output. My questions are:

1. My famiclone has a constant loud buzzing, and I wonder if the mod may fix that.
2. I would like to get a schematics of the audio part of the original famicom, to compare it with the circuit in my clone.

Thanks!!

[80sFREAK]

First check your soldering, shields, ground. Replace capacitors around voltage regulator. You also might need to replace '368.

I take audio from pin46 via 1kOhm resistor, if you want to add capacitor there, 22uF is enough. "Minus" is out.

[aha2940]

Thanks for your reply, 80sFREAK.

What is the effect of having a capacitor in the audio output? will it reduce the audio buzzing? will it improve the audio somehow? how does changing the capacitance affect the audio output?

Thanks!

[jpx72]

famicom schematics - http://jpx72.detailne.sk/modd_files/fc/schematics/schema.htm
here's NES:
http://www.freeinfosociety.com/electronics/schemview.php?id=2405

[aha2940]

Thanks a lot for your help, jpx72. That schematics is exactly what I was looking for to understand better the audio part in the famicom.

80sFREAK: thanks for your suggestion, I'll check the solder points in the famiclon and compare the circuit with the schematics jpx72 pointed. Hopefully, I will be able to improve the audio on my clon

Thanks again guys!!