IBM 3270 Maintenance Manual page 327

Check the fixed disk drive voltages.
1. Connect the fixed disk drive power supply
connectors.
2. Refer to the figure below for the proper
voltage values. The voltages should be the
same on both fixed disk drive connectors.
Fixed Disk Drive Power Connector
Min Vdc MaxVdc -Lead
+
Lead
+
4.8
+
5.2
2 4
+
11.5
+
12.6
3
1
Power Connector
/'\
Type 1
Type 2
ARE THE VOLTAGES WITHIN THE
SPECIFIED VALUES?
NO Replace the expansion unit power supply
(see Section 5, "Removal/Replacement and
Adjustments").
YES
3-1800-12 Maintenance Information