Diagnostic Information; Start; Voltage, Ground, And Continuity Readings - Lexmark 2390 003 - B/W Dot-matrix Printer Service Manual

2. Diagnostic Information

Start

Make a quick visual check for defects (loose or broken parts,
unplugged connectors, paper jams, and so on).

Voltage, Ground, And Continuity Readings

Voltage Readings
All DC voltages must be within +5% through -10% of the values to
be considered correct. Unless stated otherwise, all connectors
should be connected normally when a voltage measurement is
done.
When a "Line Voltage" measurement is to be done, the voltage on
United States and Canada machines should be between 100 V ac
and 127 V ac. On World Trade machines, the voltage is according to
each country's specification.
Ground Checks
To check for a correct ground, measure the voltage between the
ground and a known good voltage source. The voltage
measurement must be the same as the source voltage to consider
that the ground is correct. Continuity measurements may be used to
check grounds, however, be sure to measure to a known good
ground using the lowest ohms scale and check for zero ohms.
Note: Always unplug the power cord before doing any continuity
measurement.
Continuity Readings
When measuring continuity, be sure no back circuits affect the
measurement. If necessary, unplug connectors to remove any back
circuits. Zero the ohm range on the lowest scale (X1). An open
circuit will read infinity. A circuit with correct continuity will read zero
ohms.
Diagnostic Information 2-1