TG 16 Sound Issue - Not a cap problem

[rxmage]

I am hoping someone can help point me in the right direction on an issue I am having with audio.  I picked up a TG16 knowing that it had a sound issue.  I was hoping that it simply needed a cap kit, but unfortunately, that is not the case.  When testing the unit, it sounds as if one of the sound channels is simply missing.  As I had the cap kit available, I went ahead and installed it with no change.  While performing the cap kit install, I searched for any bad traces, but didn't find any.  I get continuity from pins 17 & 18 from the Hu6280 to their respective pins on the expansion port (I am pulling composite video and stereo audio from the expansion port pins.  The RF modulator has been removed).

To test the sound, I used Ninja Spirit's sound test.  The music plays, but there is a continuous tone playing while the music plays.  This tone is persistent even when you stop the music.  I don't know if this could be a ram issue at IC102 or not.  Possibly the Hu6280 could be bad. 

There aren't any graphical issues and games play fine...just with sound that is just not quite right.  Any suggestions would be greatly appreciated.

Thanks
Chad

[Vimtoman]

NEC in their infinite wisdom did not buffer or protect the expansion bus so it's vunberable to static ect.
Their is a possibility that the HUC6280 is damaged on one of the audio pins.
If you have a scope you could check the pin.
Here is a a link for schematic.
http://console5.com/wiki/File:TurboGrafx-16-Schematic-1-Hu6280_Circuit.png

Hope thats helps some.

[rxmage]

Thanks for the reply!  After poking and prodding at it some more, I am pretty sure that the Hu6280 has failed in the audio section.  I didn't bother to hook my scope up to it, as replacement CPUs are not readily available...confirming my suspicions would not get me anywhere.  Too bad, other than glitchy sound, the unit works fine...even has an a/v mod.  Will probably keep as parts.  Who knows, might come across a damaged board set that has a working CPU and I can bring it back to its full working glory!

Thanks again,
Chad