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Troubleshooting Procedures
1780R-Series Service Manual
6–23
DC Power Supply: Variable voltage supply, 0–20 V DC at 1A.
For example: A TEKTRONIX PS 503A Power Supply.
(Requires a TM500-Series mainframe.)
Isolation Transformer: For example: Stancor GIS 1000.
Test Oscilloscope: See Equipment Required List for the Performance Verification
or Adjustment Procedures.
5 V Supply Load Resistor: 47 W, 1W resistor.
A Resistive Dummy Load: See Step 18 for resistance values.
1. Unplug the 1780R-Series from the AC mains.
WARNING. Turning off the 1780R-Series Power switch does not remove mains
potential from the power supply circuits. Unplug the 1780R-Series power cord.
2. Connect a shorting strap from U360 pin 3 to ground. Connect the external
DC power supply leads between TP560 (+) and TP460 (–). See Figure 6–6.
WARNING: Be sure that the 1780R-Series power
cord is unplugged before connecting external power
supply leads.
Figure 6–6: Connections for the external power supply leads
3. Turn on instrument front-panel POWER switch.
4. Connect the test oscilloscope probe to the base of Q250, ground to TP460
along with the external power supply common lead.
Equipment Required List
Procedure