General process for System 3 sound boards...
...Reset working?
...clock signal working?
...ROMs valid?
...RAM working?
...address and data lines working?
Proper boot will cause the LED to blink.
You’ve been through most of this.
—
Chris Hibler - CARGPB #31
http://ChrisHiblerPinball.com/contact/
http://www.PinWiki.com - The new place for pinball repair info