ilmenator Posted July 8, 2003 Report Share Posted July 8, 2003 Hi Thorsten,in your wiring diagram (http://www.ucapps.de/mbhp/mbhp_4xsid_c64_psu_optimized.pdf) you say that you measured a s/n ratio of about -76dB for the 6581 chip. Did you use the same schematics for powering the 6581 chip, including the 7809 voltage regulator? Or did you replace the voltage regulator with a 7812?Which PSU did you use? The one from the "old" C64 ("Brotkasten", originally supplied with the model that you used the case for the MBSID) or from the newer C64II one? Does this matter, or are they electrically speaking the same?Thanks, ilmenator Quote Link to comment Share on other sites More sharing options...
TK. Posted July 9, 2003 Report Share Posted July 9, 2003 Hi Ilmenator,the additional 7809 is used to shift the +5VDC voltage level to +14VDC. Every SID module still requires it's own voltage regulator to convert this voltage back to 12VDC or 9VDC. Without the 7809 you would get a mixed DC/AC voltage which leads to a 50 Hz hum in the background when more than one SID is connected to the PSU. It seems that this problem is also related to a ground loop, but after I inserted the regulator for a clean DC supply this humming sound is completely vanished :)To confuse you completely: the humming sound doesn't appear when all core modules are stuffed with a seperate 7805 and powered by 9VAC, when all SID modules are powered with 5VDC + 9VAC, and when the ground pins of all voltage regulators are connected together. But I got rid of this circuit due to the power consumption (-> too much heat inside the case). The new circuit brings the best results.I'm using the PSU of a C64-A (which can be seen on the pictures). I guess that PSUs from the followers should also work, if they also deliver 5VDC and 9VACBest Regards, Thorsten./edit: we need a FAQMARKER Quote Link to comment Share on other sites More sharing options...
ilmenator Posted July 9, 2003 Author Report Share Posted July 9, 2003 Thanks Thorsten,the additional 7809 is used to shift the +5VDC voltage level to +14VDC. Every SID module still requires it's own voltage regulator to convert this voltage back to 12VDC or 9VDCthis makes it clear! Apparently, I overlooked that the voltage regulator on the SID module is still there... Only the ones for the core have been removed.So now I will have to get one of those PSUs, which seems to be far easier than building a PSU of my own.Thanks again, ilmenator Quote Link to comment Share on other sites More sharing options...
Guest Xcen Posted July 9, 2003 Report Share Posted July 9, 2003 Sorry for the dumb n00b question but what is a PSU? (searched on whatis.com and other sites and couldn't find it...)sorry :) Quote Link to comment Share on other sites More sharing options...
js Posted July 9, 2003 Report Share Posted July 9, 2003 Powersuppley ;) Quote Link to comment Share on other sites More sharing options...
Guest Xcen Posted July 9, 2003 Report Share Posted July 9, 2003 Power Supply Unit riiiiiight now I feel dumb :$ hehehe Quote Link to comment Share on other sites More sharing options...
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