IBM 4247 Maintenance Information page 131

Intermittent problems may be caused by out of range voltages. Check the voltages by following the procedures in
"MAP 0150: Power Supply" on page 75.
Electrostatic Discharge (ESD)
Intermittent problems can also be caused by build up of electrostatic charge on the forms or bad electrostatic
ground (ESD) connections. If you suspect the forms, contact level 2 support for guidance. If you suspect the
problem is caused by a bad ground, perform the following check.
Power off (O) the printer, and unplug the power cord from the customer's power outlet.
Set the meter to the lowest resistance scale and measure for 0.1 ohms or less between the ground pin of the
power cord and the following parts:
v Green/yellow wire near power switch, at the ground symbol. See Figure 24 on page 241.
v Metal plate behind the attachment cables
v Power supply through one threaded mounting screw, to the left of the ASF grounding plate
v Logic board through the threaded mounting screws, at the center of the board
v Printer mechanical assembly through the metal strips at each end
v Carriage motor, through the copper leaf spring between the motor and the plate above the motor pulley
v Any metal part of the tractor assemblies, with the tractor mounted in the printer
v ASF metal-to-metal mounting to the printer, at the 2 hooks that attach to the printer frame
v ASF bins ground-spring between bins
v ASF stacker assembly metal-to-metal mounting to the printer at the 2 latches
Attachment
Ensure that the printer is not operated with loop-back connectors installed.
Refer to the signal cable ordering information in the IBM 4247 Printer Model A00 User's Guide , SA24-4404 or the
IBM 4247 Printer Models 001, 002 User's Guide , SA24-4408, or the IBM 4247 Printer Model 003 User's Guide ,
S544–5780, for attachment cable configurations.
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Chapter 1. Diagnosing Problems