The 5V and 12V return lines should be connected together at the host system, but
these
power supply return lines should be isolated from the system frame (
)
ground. These return lines are isolated from the frame ground on the drive PCB by
a 0.01µF capacitor and 100k½ resistor in parallel. The network is provided to
suppress differential noise between the
and
grounds while providing a
connection.
Grounding for the TTL signal lines between the drive PCB logic ground and the host
system (controller) PCB logic ground should be provided by the 17 signal ground
pins of the J1 connector. All odd pins, 1 through 33, should be connected to the
controller signal ground plane.
Note:
1. Shield power cable - should be only one and tied to the ground at the filter end
only.
2. Line filter - isolated from the frame with the system ground filtered.
3. A.C. distribution - twisted pair cable including ground wire (as shown in 3 places).
The wire size must be large enough to maintain a level less than 25mV/ft drop.
4. A.C ground TB - only one connection to the frame for all
grounds and one
ground.
16
+
-
+
-
+
-
supplies
ground
Frame
4
3
2
1
Filter
5
5
5
Keybd
CRT
CPU
Drive
Drive
5
Figure 2-5. Recommended power and ground distribution
Leaflet No. 9419 26/4/97 6:09 pm Page 16
