TM 5-6675-316-14
(2) The actuating cam is rotated by the stepping motor and bears upon the
roller. This moves the font disc carriage along the slide against the spring. A
movable collar provides adjustment of the spring tension.
(3) Four constant current Darlington driver circuits supply the four row shift
motor coils to drive the stepping motor. The drivers are controlled by sequential
signals from the digital analog (D/A) stepper board.
(4) When the current in the motor coil is turned off, the collapsing magnetic
field around the coil induces voltage transients which could damage the Darlington
Q21. Diodes in the bridge CR10 bypass the spike directly to the -26 V supply and in-
directly to the +26V supply via Q12 and zener diode CR14.
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