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d. Lift the A1 board up and toward the rear, then remove the wires from the front panel switch A3S1.
A1 Designator Wire color A3S1 Position (Rear View)
A white/gray Upper right
B gray Upper left
C white/brown/gray Lower left
D white/red/gray Lower right
A3 FRONT PANEL ASSEMBLY
S1
REAR VIEW B-- | --A
C-- | --D
Install the A1 board by reversing the above steps. Be careful to follow the wire color code mentioned above.
Overall Troubleshooting Procedure
Perform the troubleshooting and repair procedures which follow only if you are trained in equipment
service and are aware of the danger from fire and electrical-shock hazards. Some of the procedures include
removing the unit's protective covers which may expose you to potentially lethal electrical shock.
Whenever possible, make test connections and perform service with the power removed.
After performing the Initial Troubleshooting Procedures, focus on developing a logical approach to locating the source of
the trouble. The underlying strategy for the troubleshooting procedures here is to guide you to the faulty circuit nodes
which have improper signals or voltages. It relies on you to identify the particular functional circuit to troubleshoot from
symptom tables and by understanding how the unit works. It then relies on you to discover the defective component or
components which cause the faulty circuit nodes. So, read the BLOCK DIAGRAM overview in Chapter 4 and read the
functional circuit descriptions for the circuits that you suspect may be defective. Then return to this section for help finding
the faulty circuit nodes.
Table 3-1 gives the signals for each of the test points on the control board test connector. This connector is provided in
service kit P/N 5060-2865. The measurements given here include bias and reference voltages as well as power supply status
signals and waveform information. To troubleshoot the power supply the A4 power FET board and A2 control board can be
raised out of the unit using extender boards and cables provided in service kit P/N 5060-2865.
The A4 power FET board should only be raised on its extender when using the Main Troubleshooting
Setup; NEVER when the unit is operated with its normal ( ≈ 300Vdc ) bus voltage. To do so can cause
damage to the unit and is a shock hazard.
Table 3-2 provides troubleshooting information based on the status of the PWM-ON and PWM-OFF signals which drive
the PFETs. This table is used for no-output failures.
Tables 3-3 and 3-4 give measurements for the test points on the A3 front panel board and possible failure symptoms
respectively.
Table 3-5 describes possible symptoms for overall performance failures of the power supply. It is necessary to have a
properly working front panel before using this table.
Chapter 6 contains schematic diagrams and voltage levels, and component location diagrams to help you locate components
and test points.