3550 Power
Power Systems Checkout
If the “power good” light is not on and if the power-supply
fan is not running, check the power cord for continuity and proper installation.
If the power cord is not the problem, either the power
supply is defective or another component is defective and is causing the
power supply to shut off. To verify that the power supply is operating
correctly, do the following:
1. Power-off the 3550 Expansion Unit and disconnect the 3550 Expansion
Unit power cord.
2. Remove all power supply connectors (power supply connector P1, P2
and drive connector 1) from the system board of the 3550 Expansion Unit
and SCSI device.
3. On power supply connector P2, short-circuit pin 4 to pin 6 and short-circuit
pin 7 to 8.
4. Connect the 3550 Expansion Unit power cord.
5. Check the power supply voltages using the figures on the next page.
Drive Connector
1
Standard 4 pin molex
|
Pin
|
Signal
|
V dc Min.
|
V dc Max.
|
|
1
|
+12 volts
|
+11.52
|
+12.6
|
|
2, 3
|
Ground
|
|
|
|
4
|
+5 volts
|
+4.8
|
+5.25
|
If any of the voltages are not correct, replace the power supply.
If all voltages are correct, the power supply is working
properly. Another 3550 Expansion Unit component might be causing the power
supply to shut off.
Power Supply Connector
P1
|
Pin
|
Signal
|
V Min
|
V Max.
|
|
1 2 3 4
|
+5 volts
|
+4.8
|
+5.25
|
|
5 6 7 8 10
|
Ground
|
|
|
|
9
|
+20 volts
|
+19.0
|
+21.0
|
Power Supply Connector
P2
|
Pin
|
Signal |
V Min. |
V Max |
|
1 2
|
+12 volts
|
+11.52
|
+12.6
|
|
3
|
Power Good
|
+4.0
|
+5.25
|
|
4
|
On/Off Signal
|
|
|
|
5
|
-12 volts
|
-10.92
|
-13.2
|
|
6 7
|
Ground
|
|
|
|
8
|
Global Signal
|
|
|
9595 Main Page
|