C64 sound problems
hilpert at cs.ubc.ca
Thu Jul 23 12:15:43 CDT 2009
David Betz wrote:
> I finally got around to checking the 12v supply in my C64 and it seems
> to be working. I also verified that 12v is getting to the VDD pin on
> the SID chip so lack of 12v is not my problem. One thing I noticed
> that I thought rather strange was that the VCC pin on the SID reads
> 5.27v but the output of the 5v regulator is correct. Is there a reason
> why the VCC at the SID would be higher? Could this be causing a problem?
Further, pin 27 is the audio output from the SID, it feeds a transistor (Q8) in
emitter follower cfg.
The emitter of Q8 feeds the RF modulator and pin 3 of the audio/video
connector. Might check or 'scope around those.
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