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Display Backlight Inverter Board
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
sig nal determines the lamp bright ness. Displays by some
manufacturers have two lamps; one at the top and one at
the bottom of the display. Other Display man u fac tur 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 60K Hz signal that
is applied to the lamp. The higher the AC voltage, the
great er the bright ness of the lamp. When this voltage is
not present, the lamp is turned off.
High voltage, up to 1500VAC, is
present at the out put of the back light
in vert er board. Refer to Fig ures 29 to
31 and locate the out put con nec tors.
Use ex treme caution when work ing in
this area!!!
Different Display manufacturers require different Back-
light Inverter Boards. The different board designs re quire
different control voltage inputs. To ac com mo date these
variations, Microboard Program Jump ers JP3 - JP5,
JP7 and JP8 must be confi gured to provide the required
voltage levels. A label at tached to the Display mounting
plate lists the required Program Jumper con fi g u ra tion
for that particular display. Refer to Table 1 for required
Program Jumper confi gurations for the var i ous Display
applications.
Under Program control, the Microboard generates the
control signals that are applied to the Backlight In vert er
Board. The Program determines when the lamp is turned
on and off. It also adjusts the lamp brightness. To in-
crease the average lamp life of 25000 hours, the lamp
brightness is normally adjusted to 50%. This bright ness
level will still allow the display to be visible. When the
Program senses a Keypad key has been pressed, it ad justs
the brightness to 100% (maximum).
The lamp illumination high voltage AC is generated
from either +12VDC or +5VDC as required by the
man u fac tur er. Microboard Program Jumper JP5 must
be po si tioned to provide the required voltage. The
Microboard provides the Backlight Enable sig nal. This
56
SECTION 7
(REFER TO FIG. 29 - 31)
sig nal turns the lamp on and off. Some man u fac tur ers re-
quire this sig nal to be +12VDC, others re quire +5VDC.
Pro gram Jumper JP4 must be po si tioned to pro vide the
re quired voltage. Further, some ap pli ca 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 po si tioned
to pro vide 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 Fig. 10). The lamp dim-
mer circuit on the Microboard is an IC that is the elec-
tri cal equivalent of a 10K ohm po ten ti om e ter with 100
po si tions or steps. The Program adjusts the position of
the potentiometer. When confi gured for variable volt age
(JP7 & JP8 installed), the output between Microboard
J6-7 and J6-8 is a 0 to +5.0VDC signal. Not all applica-
tions require the full 5.0VDC range. If con fi g ured for
variable resistance (JP7 and JP8 re moved), the out put
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 sev er al approved Displays. Each Display re-
quires a spe cifi c Back light Inverter Board as speci-
fi ed below and in Figures 29 to 31. These boards are
individually avail able as service replacement parts (the
required Back light Inverter Board part number is listed
on the label at tached to the Display mounting plate).
How ev er, ser vice replacement Displays are provided
in a kit (YORK P/N 331-01771-000) that includes the
appropriate Back light Inverter Board (refer to "Liquid
Crystal Display" Section).
SHARP model LQ10D367 AND LG Semicon LP104V2-
W displays re quire a TDK CXA-LO612-VJL Backlight
In vert er Board (YORK P/N 031-01789-000) (ref. Fig.
29). These boards gen er ate a lamp il lu mi na tion high
voltage AC from +12VDC. When the Back light Enable
signal at con nec tor CN1-3 is +5VDC, the high voltage
signal is applied to the lamp. When CN1-3 is 0VDC, the
high voltage signal is re moved from the lamp, turning
it off. The lamp bright ness is controlled by a variable
volt age signal, de vel oped by the lamp dim mer circuit
(ref. Fig. 10) on the Microboard and ap plied to connector
FORM 160.54-M1(503)
YORK INTERNATIONAL
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