Star Tech Journal

6
STAR•TECH JOURNAL/AUGUST 1982
WELLS-GARDNER
VERTICAL DEFLECTION CIRCUIT REVISION
GRN
DRIVE
RED
DRIVE
NEG H SYNC
NOTE:
WHEN USING
COMPOSITE SYNC
USE HORIZONTAL
SYNC INPUTS.
GND
BLU
GRN
RED
HORIZ
CENTERING
VERT VERT
VERT
VERT
SIZE HOLD DAMPING RASTER
SHIFT
1. Identification
This bulletin applies to those monitors with serial
numbers of 400001 and above.
They can be identified by the following:
A) The model number on the shipping carton and
on the monitor is printed in red.
B) The part number on the deflection yoke is
either 2021111258 or 2021111264.
C) The flyback transformer stabilizing bracket is
labeled 611X0005-008.
D) There is an additional control, the
VERTICAL DAMPING CONTROL, shown
above, immediately to the right of the Vertical
Hold Control.
HORIZ
RASTER
SHIFT
SCREEN
All K4900 Series
Monitors
including, but not
limited to, the
following model
numbers:
K4901
K4902
K4906
K4911
K4951
K4952
K4956
K4956R
K4961
CONTROL is important only if the vertical size
is adjusted such that the additional lines appear on
the screen. Turn up the Black Level Control such
that the raster lines can be seen. Adjust the
Vertical Damping Control such that the top raster
lines are spaced uniformly and not folded over.
Return the Black Level Control to the desired
setting.
2.Reason
The applicable monitors have an improved
deflection yoke which provides for faster vertical
retrace. This permits more lines of video to be
displayed. The VERTICAL DAMPING
CONTROL permits the user to adjust the
uniformity of spacing of the additional lines.
4. Yoke Replacement
It is IMPERATIVE that deflection yokes with part
numbers 202111125 8 and 2021111264 be used
only with the chassis identified above. They may
not be substituted for deflection yokes with part
numbers 2021111194 or 2021111201.
Conversely, deflection yokes numbered
2021111194 and 2021111201 may not be
substituted for deflection yokes numbered
2021111258 and 2021111264. Improper
matching of chassis and yokes will result in
insufficient vertical deflection or improper
blanking operation.
3. Adjustment of the Vertical Damping
Control
The adjustment of the VERTICAL DAMPING
NOTE: When requesting service parts or information,
be sure to mention the monitor's model
number and serial number.