IBM 6400 Series, Maintenance Manual

Page: 51 / 428

51
Principles of Operation
The printer uses five motors: two ribbon drive, one paper feed, one platen
open, and one shuttle motor. The shuttle motor is a brushless DC motor
driven by current control. The MPU encoder is used as feedback for motor
commutations, hammer fire timing, and motor stall detection. The paper feed
motor is a DC stepping motor driven by current control. The paper feed motor
may be driven in full, half, or microsteps, depending on print requirements.
The ribbon system uses two DC stepping motors that alternate drive and
drag roles when the ribbon reaches turnaround. The drive ribbon motor is
microstepped in voltage mode, while the drag motor is loaded and monitored
to maintain correct linear speed and tension. The platen motor is driven in
current mode and can be full or half stepped. The overall current level may
be reduced for standby modes.
The paper feed, ribbon drive, and shuttle motors are driven in control loops
containing power MOSFETs, voltage and current sensors, the MECA ASIC,
and the EC processor. The platen open motor is driven by a stepping motor
controller IC and the EC processor.
Control of the hammer drive is split between the controller board and the
hammer bank. Common circuits are located on the controller board, while
hammer specific circuitry is contained on the hammer bank. The EC uses the
MECA ASIC on the controller board to set timing and upper drive profiles for
hammer fire events. The controller also contains diagnostic circuitry for the
hammer system. The hammer bank contains HBA ASICs that interpret fire
commands and data from the MECA and VX ASICs. The HBAs control lower
drive MOSFETs on the hammer bank. These determine which hammers will
participate in a fire event generated by the controller’s upper drive.
Power Supply Board
The printer power supply is contained on a printed circuit board mounted in
the card cage. The power supply automatically senses and adjusts to any
commercial electrical system that provides AC mains potential in 50 or 60
Hertz systems. In other words, the printer is fully operational from available
commercial power anywhere in the world.
The power supply converts alternating current (AC) to direct current (DC) at
three voltage levels and sends the DC voltages to the controller board. The
controller board distributes all DC power to the logic and electromechanical
circuits.
AC Power
The power supply operates on AC voltages ranging from 88 to 270 V. It can
tolerate variations in frequency of 47 to 63 Hz. The power supply is designed