Section 8 - Display Backlight Inverter Board - Johnson Controls YORK OPTIVIEW YK Series Service Instructions Manual

FORM 160.54-M1

SECTION 8 - DISPLAY BACKLIGHT INVERTER BOARD

The Display Backlight Inverter Board generates a high
voltage AC signal that is applied to the backlight lamp,
causing it to illuminate. The magnitude of the signal
determines the lamp brightness. Displays by some
manufacturers have two lamps; one at the top and one
at the bottom of the display. Other Display manufactur-
ers have only a lamp at the top of the display.
An Inverter converts low level DC voltage (+12VDC
or +5VDC, as required by the manufacturer) from the
microboard to a 500 to 1500VAC 60KHz signal that
is applied to the lamp. The higher the AC voltage, the
greater the brightness of the lamp. When this voltage is
not present, the lamp is turned OFF.
High voltage, up to 1500VAC, is present
at the output of the backlight inverter
board. Refer to Figure 38 on Page 92
to Figure 40 on Page 95 and locate the
output connectors. Use extreme caution
when working in this area!
Different Display manufacturers require different
Backlight Inverter Boards. The different board designs
require different control voltage inputs. To accommo-
date these variations, Microboard Program Jumpers
JP3 through JP5, JP7 and JP8 must be configured to
provide the required voltage levels. A label attached to
the display mounting plate lists the required Program
Jumper configuration for that particular display. Refer
to required Program Jumper configurations for the var-
ious Display applications.
Under Program control, the microboard generates the
control signals that are applied to the Backlight Invert-
er Board. The Program determines when the lamp is
turned ON and OFF. It also adjusts the lamp bright-
ness. To increase the average lamp life of 25,000 hours,
the lamp brightness is normally adjusted to 50%. This
brightness level will still allow the display to be vis-
ible. When the Program senses a Keypad key has been
pressed, it adjusts the brightness to 100% (maximum).
The lamp illumination high voltage AC is generated
from either +12VDC or +5VDC as required by the
manufacturer. Microboard Program Jumper JP5 must
be positioned to provide the required voltage. The mi-
croboard provides the Backlight Enable signal. This
signal turns the lamp ON and OFF. Some manufactur-
JOHNSON CONTROLS
ers require this signal to be +12VDC, others require
+5VDC. Program Jumper JP4 must be positioned to
provide the required voltage. Further, some applica-
tions require this signal to be a +VDC (+12VDC or
+5VDC) to turn on the lamp. Others require this signal
to be 0VDC to turn on the lamp. Program Jumper JP3
must be positioned to provide the required polarity.
Depending upon the Display manufacturer, the bright-
ness control input from the microboard must be either
a variable voltage or a variable resistance. Microboard
Program Jumpers JP7 and JP8 are used to provide the
appropriate technique (Refer to Figure 13 on Page
43). The Lamp Dimmer circuit on the microboard is
an Integrated Circuit (IC) that is the electrical equivalent
of a 10K ohm potentiometer with 100 positions or steps.
The Program adjusts the position of the potentiometer.
When configured for variable voltage (JP7 and JP8 in-
stalled), the output between Microboard J6-7 and J6-8 is
a 0 to +5.0VDC signal. Not all applications require the
full 5.0VDC range. If configured for variable resistance
(JP7 and JP8 removed), the output between Microboard
J6-7 and J6-8 is a 0 to 10K ohm variable resistance.
The OptiView™ Control Center could be supplied
with any of several approved Displays. Each Display
requires a specific Backlight Inverter Board as speci-
fied below and in Figure 38 on Page 92 to Figure 40
on Page 95. These boards are individually available
as service replacement parts (the required Backlight In-
verter Board part number is listed on the label attached
to the display mounting plate). However, service re-
placement Displays are provided in a kit (YORK P/N
331-01771-000) that includes the appropriate Back-
light Inverter Board (Refer to SECTION 6 - LIQUID
CRYSTAL DISPLAY).
SHARP model LQ10D367/368 (031-01774-000) and
LG Semicon LP104V2-W (031-02046-000) displays
require a Backlight Inverter Board 031-01789-000
(Refer to Figure 38 on Page 92).
SHARP model LQ104V1DG61 display (031-02886-
000) requires Backlight Inverter Board 031-02889-000
(Refer to Figure 39 on Page 94). These boards gener-
ate a lamp illumination high voltage AC from +12VDC.
When the Backlight Enable signal is +5VDC, the high
voltage signal is applied to the lamp. When the Enable
is 0VDC, the high voltage is removed from the lamp.
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