Famicom Sound Problems

[MBombchu]

Hey Guys,

I am trying to mod this Famicom for AV, starting with audio, however, i can't get any audio from it.
With RF it's fine btw.

Pin 46 goes straight to the tip of chinch
and GND is taken from above.
I get about 2.5V at the chinch plug.
http://www.mediafire.com/view/s6p55c5c1nmffl7/20150401_170900.jpg

ANY HELP IS APPRICIATED !!!

Thanks

[jpx72]

Have you tried different TV to test? Or just use another cable and cinch...
Does sound on RF work?

[MBombchu]

Yeah i tried different cables and tvs, but it worked on none of them. Sound on RF is fine

[number47]

You could try to tap for separate audio channels on CPU pins 1 or 2

[jpx72]

have you separated the signal with a capacitor?

[MBombchu]

No, i didn't try that, as i often heared it would work without a capacitor

Post Merge: April 03, 2015, 07:59:10 am
I didn'tt change anything since yesterday, but now the RF sound is much too high pitched on some parts, while othery sound perfectly fine !?! Capacitor failure ?

[jpx72]

What capacitor do you have? What about polarity (plus minus)?
www.jpx72.detailne.sk/modd_files/fc/avmod/sound.png

[MBombchu]

But why is the RF sound wrong now i didn't solder anything !?!

[jpx72]

Desolder everything you did, if the RF sound is still wrong, the problem is somewhere else. Maybe voltage regulator is bad, or you have bad adapter. Looks like voltage problem.

[MBombchu]

I desoldered everything. Sound is normal at startup, but gets disorted after some minutes of gameplay
Post Merge: April 04, 2015, 10:22:40 am
it cant be my power supply, as i use it on my av-fc without problems

[jpx72]

Something must be overheating, can be CPU or RAM or... hard to say. Try the cheapest, exchange voltage regulator 7805.

[MBombchu]

Ok thanks. Gotta rob my nes for a 7805

[jpx72]

One thing, try to cut line from pin46 to the rf part and try cinch again. Maybe something on the small PCB, some failing capacitor (like mentioned earlier).

[MBombchu]

But what i can't get is that deep sounds soubd normal, only high ones get pitched

[jpx72]

I had similar problem on a famiclone, high tones were too high, squeaky...  exchanging CPU solved the problem.