H/P Bench Supply Question

[john miller]

I recently got a used  Hewlett-Packard 6200b DC Power Supply and I'm 
having trouble getting a +, -, and GND at the same time. If I connect my
mutimeter from + to - I get a + voltage (correct voltage). If I connect
from + to GND I get  0.00v reading. I have noticed on the back of the
supply there is a strip connector with A1-9, S-, -, Gnd, +, S+, and 
A10. Do I need to make a connection on the back to use the supply as a
+,-,Gnd type?  I had been using a power supply I pulled out of an old
ARP and wondered why everything I have built since I got the H/P supply
wouldn't work!

Thanks
John