I finished my Sid and Core modules and voltages were Ok. Then I interconnected them and, when I power them both, Sid voltage drops to 2.4  If I only power the Sid module, even with both interconnected, the voltage´s fine, but as soon as I power the Core module, it drops again. ??? (no IC´s)
  Damn, I was so close…
What PSU are you using?
Which Voltage is dropping: 12/9V or 5V?
When you connect 12/9V and 5V to the SID only, what do you get?
I´m using a 15v-1.0A wallwart. Sid voltage drops from 12v to 4.5v, and the 5v drops to 3.8 now. ???
I´m using a 15v-1.0A wallwart. Sid voltage drops from 12v to 4.5v, and the 5v drops to 3.8 now.
What do you mean with “now” ??? here is the difference to your first setup?
Could you give any more details? Like at which pins you connect what and so on…
In general: Recheck your PCB for bad soldering or solder joints again and again and…
The problem´s solved now ;D It was the wallwart. Cheap crap!
So have fun with your SID ;D ;D ;D