Hughes JVC Projector 250 Service Manual

Chapter 2---System Description
2-4 Model 250 Service Manual
! Condensing Lenses (2) - The Primary Condensing Lens collects all the
light from the Light Pipe and begins to bend the light rays into a straight
path. The Secondary Condensing Lens works with the Primary
Condensing Lens to collimate or “straighten” the light path before it enters
the Dichroic Beamsplitter Assembly.
! UV Filter - The UV Filter removes much of the unwanted ultravioltet light
from the white light of the Arc Lamp.
! Dichroic...

Chapter 2---System Description
Model 250 Service Manual 2-5
Relay Lens Assemblies (3)
There are three Relay Lenses, one for each color. The Relay Lens focuses the
image light from the CRT onto the photosensitive layer on the input side of the
ILA
®. The Relay Lens is physically connected to the CRT (see Figure 2-2).
Front Projection Lens
The Model 250 comes with a choice of four standard lenses. These include a
motorized Zoom Lens or one of three Fixed Lenses. All Projection Lenses have
motorized focus....

Chapter 2---System Description
2-6 Model 250 Service Manual
Printed Circuit Boards (PCB)
The Model 250 Projector has eight main PCBs:
! System Controller PCB - System Controller PCB controls much of the
electronics system. It uses digital and analog circuitry to generate Menu
and internal pattern overlays, and directs convergence correction and
shading information. It controls the IIC data bus that sends geometric
correction and VIC selection data. The System Controller PCB controls
and monitors the...

Chapter 2---System Description
Model 250 Service Manual 2-7
provides an interconnection interface for all the electronic components in
the projector.
CRT/Yoke Assemblies
The CRT/Yoke Assemblies bridge between the Optical and the Electronic
sections. The CRTs could be included in the Optical section because they
produces the image light transmitted to the ILA
®s, but they are included in the
Electronic section because they are the end user for the image signals from the
VICs, Video Processor PCB, and...

Chapter 2---System Description
2-8 Model 250 Service Manual
projector. These air-borne particles can land on optics such as the ILA® and cause
large diffuse dark areas on the screen.
EMI Shield
The Model 250 has an EMI (Electro-Magnetic Interference) Shield that traps and
collects high frequency noise that is radiated by switching power supplies such as
the Arc Lamp Power Supply and the Low Voltage Power Supply. This high
frequency noise can interfere with the operation of radios, televisions, and other...

Chapter 2---System Description
Model 250 Service Manual 2-9 

Chapter 3---Electrical
Model 250 Service Manual 3-1
3.0 Electrical
Contents
3.1  Safety............................................................................................................ 3-1
3.2  Incoming Power Circuit ............................................................................... 3-2
AC Power Cord .......................................................................................... 3-2
AC Circuit...

Chapter 3---Electrical
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Model 250 Service Manual
Left/Right Orientation: 
When referring to the left or right in this chapter, it is with
reference to standing at the rear of the projector, facing the screen.
Connectors
 on subassemblies and PCBs have tabs that must be released first
before pulling on the connector. The proper procedure is to push slightly 
IN on
the connector, then squeeze the tab, then pull the connector out.
3.2. Incoming Power Circuit
AC Power Cord
The Power Cord performs one...

Chapter 3---Electrical
Model 250 Service Manual 3-3
3.3 Power Supplies
All Series 200 projectors including the Model 250 have three power supplies.
These include:
!
 Low Voltage Power Supply
!
 Arc Lamp Power Supply
!
 High Voltage Power Supply
There is a fourth power supply, the Laser Power Supply, but that power supply is
used only for the Igniter Assembly during Arc Lamp lighting.
Low Voltage Power Supply  (LVPS)
LVPS - Main Functions:
!
 Provides all the low voltages needed by the projector.
!...

Chapter 3---Electrical
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Model 250 Service Manual
Figure 3-1  
Low Voltage Power Supply I/O Diagram.
LVPS - Operation:
AC power is delivered to the Low Voltage Power Supply from the AC line filter.
The AC is rectified to a DC Voltage, filtered, and goes through a power factor
correction circuit to force the current waveform to follow the voltage waveform.
The +5.1V Standby is on whenever AC power is connected to the projector and
the circuit breaker on the rear panel is in the ON position. When the AC...