I am hoping to find a schematic for the A3 source board. This is not included with the Agilent schematics that I have on hand. For some reason, A3 was left out of the book. My A4 sampler board is also bad, and I have traced the problem to the gold sample "head". No current will pass through it. I hope someone can shed some light on what components are contained in the "head" and if anything can be done.