NCR 7156, Руководство по обслуживанию

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7156 Service Guide Chapter 4: Troubleshooting
September 1998 43
Chapter 4: Troubleshooting
This chapter gives information on test points and Field Effect Transistors (FETs), and
provides tables to help in determining the cause of printer malfunctions.
Test Points
Test points are located on the PC board and can be used to diagnose sensor and power
failures. Interruptive sensors flip-flop between 0 and 5 volts when an object is moved in
and out of the slot between the photocell and the LED. Reflective slip sensors have LED
circuits that are pulsed and cannot be checked with a simple voltmeter.
The test points and their functions are listed in the following table:
Test Point Name Function Normal State
LG Logic Ground
PG Power Ground
VCC +5 Volt Logic
V24 +24 Volt Power
RESET PCB Reset Low Active
THM Thermistor 1.1 to 2.4 Vdc
MICR MICR Input Signal 0 to 2.5 Vac
VP Thermal Printhead Voltage 21.6 to 30.8 Vdc
CASDR Cassette Door Low Open
RCPFD Receipt Feed Low Active
RCPEX Receipt Exhaust High Exhaust
RCPDR Receipt Door Low Open
KNFHM Knife Home High Home
SENS1 Front Slip Sensor Pulsed Low in
RSLP Rear Slip Sensor Pulsed Low in
TSTRP Carriage Timing Sensor Strobed for Motion
PRTSOL Print Solenoid Pulsed High Active
C_SLP Slip Feed Motor Chop .4 to .6 Vac
C_CAR Carriage Motor Chop .4 to .6 Vac
RCPLOW Receipt Paper Low Low