The RCLK pulse is high for ca. 200 nS some cycles before the CS# will be activated
Which timebase are you using? Maybe it’s too short so that your scope doesn’t trigger on this pulse?
Check it also without the SID module - if the pulse is available thereafter, you’ve a short on your SID module…
Another point which should be checked: how long are the cables between the core and the SID module? Does it work when you shorten it?
Best Regards, Thorsten.
Thanks a million Thorsten!!! Finally my SID has come to life, and now it is making some beautifull sounds!!!
Turned out to be a short between two HC595 pins, the short was hardly visible but your tip on RES# indicated that it had to be there somewhere. With the smallest timebase (on my older scope) I could just barely see the RCLK, so this was ok. Tracing the signals and the aid of HC595 datasheets lead to the cause of my problems.
Now only some example patches won’t play, like c64 bass and 6581 filtered bass. I suspect the that LowPass filter over OSC1 is not working, the 470nF capacitors look ok so maybe this filter of the SID is fried. I also hear a loud ‘plop’ sound when changing patches. I guess it’s normal, but maybe this is caused by the faulty filter section??
Again, thanks a lot! When I finished it I’ll send you a picture! Now I can go back to what I like most: make music 
Trapstate
Hi,
you possibly have to disable the CBM8580_FILTER_FIX switch in main.asm
Have fun! 
Best Regards, Thorsten.
Burnt the PIC with the filter fix disabled, but still some patches don’t play. This has something to do with filters on OSC1, but first I will have to test some more. Maybe first I will stuff another SID, if I can find a defect C64 (Don’t want to hurt C64’s wich are still alive) I now have 6581/ 3984
trapstate