User`s guide

User’s and Service Guide 6-21

Service

Troubleshooting and Block Diagram

This section contains information on troubleshooting the test set to the

assembly level only. By following these procedures you should be able to

determine whether the power supply, front panel, or main switch board

needs replacing. A block diagram is included at the end of this section

as an aid in troubleshooting.

Theory of operation information can be found in the next section of this

manual.

General Troubleshooting Notes

WARNING Always turn the instrument power off before removing or

installing an assembly.

CAUTION If you need to disassemble the instrument, be sure to work at an

antistatic workstation and use a grounded wrist strap to prevent

damage from electrostatic discharge (ESD). See Figure 1-3 on page 1-7.

Troubleshooting Power Supply Problems

Turn the instrument on. Check the condition of the LCD on the front

panel:

Step 1. If the LCD is off, check the main fuse located in the power supply filter

at the rear of the instrument and replace if necessary.

Step 2. If the LCD is still off, there is still a possibility that the power supply is

not supplying the necessary +24V, +12V, and +5V to the main board.

Step 3. If the LCD is still off, check the cable between the main board and front

panel board.

Step 4. Finally, disconnect the DC power cable from the power supply to the

main switch board and measure the voltages. They should be +24V,

+12V, and +5V. If not, replace the power supply.