23 Jul
2009
23 Jul
'09
10:15 a.m.
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.