Hi Andy. The inst. cluster supplies the bias, I believe, for the CCD bus pins 3@11 in ALDL. The volt. at these pins, with DVOM to grd., should be close to 2.5V to grd. pin 3 (CCD bus+) and +/-.02V observed in pin 3, in pin 11(CCD bus -) to grd. Since the IP is... Login to read more.