PV152
2-16
PRO1200 CIRCUIT DESCRIPTION
CIRCUIT DESCRIPTION
The series output resistor in the unit forms, together
with P2, P3, P4 and R17, a divider. If we stabilize the
voltage at the
R253
“Adjust for 1020V with P1” we also
have a stable G2 voltage on the sliders.
That 1020 volt point is sensed with the divider R15 /
R13/ P1. Since the Vref is 10 volt, the output of the
OPAMP will change until pin 13 is at the same voltage
level of 10 volt.
Any voltage difference due to a change of the 1020 volt
is adjusted by Q2 which will feed a current from R252 to
the (negative) output of the OPAMP.
Q2 is needed because the 1020 volt is a too high volt-
age for the OPAMP. A high voltage transistor such as
BU508A is therefore required.
E. LEDs for diagnosis
(Page 6-4 Sect. A-3 to 6)
The presence of the various voltages are all displayed
with green LEDs. The variable voltages, like the +HTHD
and +CONV, drive an LED through a transistor to obtain
a constant light output of the LED.
The scan fail diode D16 is red and shows a problem in
the horizontal or vertical deflection.
809-10466
The Power (Main) Input provides protection against in-
terference when operated in a commercial environment
and contains the user setting for 230Vac or 120Vac.
1. Power (Main) filter
The power filter consists of coil L1 with four windings,
and capacitor C3. It is a filter, blocking all high and low
frequency noise towards the outlet.
NTC-resistors NTC1, NTC2 and NTC3 limit the start up
current. Fuses F1 and F2 prevent damage to the power
input board and the Switched Mode Power Supply in the
event of short circuit or wrong 230/120Vac setting.
2. 230 Vac operation
Diode bridge D100 of the Switch Mode Power Supply is
connected to the power Input board. It operates as a
bridge rectifier, and we get an output DC-voltage of
approxi300 Volts.
Capacitor C103 forms a capacitive load on the Switch
Mode Power Supply, to flatten the AC-ripple on the +300
DC-voltage. Resistor R103 discharges this capacitor
quickly when the projector is switched off.
3. 120 Vac operation
The diode bridge of the Switch Mode Power Supply is
connected to the Main Input/Output board during
130Vac operation and operates as a voltage multiplier.
(Note that NTC1, NTC2, and NTC3 only play a roll during
start up, and R3 and R4 are only important while switch-
ing off.)
During the negative half period of the power (Main)
voltage, capacitors C11-C12 are charged through the
bridge rectifier. During the positive half of the power
(Main) voltage, capacitors C9-C10 are charged through
the bridge rectifier with a voltage which is the input
voltage together with the load on the capacitors C11/
C12.
In this way a DC-voltage of approxi300 Volts is
built across the capacitor C.
MAIN (POWER) ADAPTATION PROCEDURE:
1. Switch off the projector and unplug the power plug
from the wall outlet.
2. Open the Top and the Module rack cover
3. Loosen the lock screw of the power input module and
pull out this module.
4. Pull out the “POWER SELECTOR PLUG” and re-insert it
as illustrated below depending of the wall outlet in the
room.
5. Replace the fuses.
6. Re-insert the power input module and secure it with
the lock screw.
7. Reconnect the power cord with the wall outlet and
switch on the projector.
Scan inversion
S1, S2 and S3 allow the horizontal scan to be inverted
to adapt the projector for a front or rear projection.
S3 is also used to provide the HSI_[CTRL] information
to the controller board, so that the controller board will
know the configuration of the horizontal scan switches.
S3 is also used to provide the HSI_[FOC] information to
the “HOR SHIFT” module and is used by Q1 and Q2 to
invert the shift voltages on P1 and P2 (horizontal shift
Red and Blue).
Note that the main board also contains the switch for
the inversion of the vertical scan. The VSI [CTRL] info is
used for the controller and the VSI [VERT] info for the
Vert Defl board (similar to Hor Defl).
