Hughes JVC Projector 250 Service Manual

							Chapter 3---Electrical
Model 250 Service Manual 3-5
!
 +5.1V for digital components
!
 +6.2V for CRT filaments
!
 ±15V for analog circuits
!
 +80V supply used by the High Voltage Power Supply, Video Amplifier
PCB, and the Horizontal/Vertical Deflection PCB.
LVPS - Service Adjustments
There are no service adjustments for the Low Voltage Power Supply.
LVPS - Remove and Replace
Tools Needed:
#2 Posi-drive Phillips-head screwdriver
Parts Needed:
Low Voltage Power Supply - p/n 102520
To remove the Low Voltage Power Supply:
1. Power off the projector by IR Remote or PC, and allow the cooling fans to
run until they shut off.
2. Turn the AC Circuit Breaker to the OFF position and unplug the AC
Power Cord.
3. Remove the front cover (see Projector Covers section 6.1).
4. Remove the lower-right-side panel by removing the 5 Pozi-drive screws
securing it.
5. Remove the 5 Pozi-drive screws securing the EMI Shield. Slide the shield
to the left and remove it.
6. Remove J76 (DC Output) and J75 (AC Input) from the left side of the
Low Voltage Power Supply.
NOTE
: These connectors may be a little difficult to remove and it may be
necessary to pull the LVPS partly out of the chassis in order to get a better
grip on the connectors.
7. Carefully slide the Low Voltage Power Supply out of the projector.
8. Reinstall the LVPS in reverse order. After installing a new LVPS, it may
be necessary to touch-up the Timing, Geometry, Electronic Focus, ILA®
Bias/Sensitivity, Convergence, G2, and Shading.
Arc Lamp Power Supply  (ALPS)
ALPS - Main Functions:
!
 Provides ignition power to turn the Arc Lamp ON (via the Igniter).
!
 Provides steady state power to maintain the Arc Lamp operation. 
						

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ALPS - Inputs:
AC input power: Directly from the AC Line Filter. The input range is from 220-
240 VAC, at 50/60 Hz.
/LAMP_ENA - from the System Controller PCB. Turns on the ALPS.
/COVER_ON - signal enabling the Arc Lamp Power Supply.
/LAMP_OK  - the input is jumpered at the Arc Lamp Power Supply (tied to
ground) so it is always low.
/ = Active Low
ALPS - Outputs:
!
 +170 VDC output during the boost phase to get Arc Lamp ignition. This
supplies the power for the Igniter.
!
 Run Voltage - 25 to 31 V to maintain the arc lamp operation.
!
 Current - 70 to 85 amps to maintain the arc lamp operation.
!
 LAMP_OUT - Lamp output voltage, positive.
!
 LAMP_RTN - Lamp return.
!
 /LAMP_LIT - signal to System Controller PCB indicating that the Arc Lamp
is lit.
!
 /LAMP_OK - signal to System Controller PCB (no real indication). 
						

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Model 250 Service Manual 3-7
Figure 3-2  
Arc Lamp Power Supply signals and voltages.
ALPS - Operation:
Three signals (/LAMP_ENA, /COVER_ON, and /LAMP_OK) are required in
order for the Arc Lamp Power Supply to light the Arc Lamp. The /LAMP_OK
(active low) input is jumpered to ground at the Arc Lamp Power Supply, so it is
always low. The Arc Lamp Power Supply sends the /LAMP_OK to the System
Controller PCB. The System Controller PCB then sends the /LAMP_ENA signal
back to the Arc Lamp Power Supply and activates the Arc Lamp Power Supply.
Once the Arc Lamp Power Supply receives the /LAMP_ENA signal from the
System Controller PCB, it supplies the +170 VDC boost voltage to the primary
coil of the Igniter. The Laser Power Supply charges up a capacitor. When the
capacitor reaches  +5.5 kV, a spark gap arcs causing a very high voltage pulse
(approximately 32 kV) to be induced onto the secondary coil inside the Igniter.
This high voltage pulse ignites the Xenon Arc Lamp. Immediately after the Arc
Lamp lights, the voltage from the Arc Lamp Power Supply drops to about 25-31
volts at 70-85 amps. It will stay at this level during normal Arc Lamp operation. 
						

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Model 250 Service Manual
The Arc Lamp Power Supply sends the
/LAMP_LIT signal back to the System Controller when the Arc Lamp is lit.
The Arc Lamp regulates its output to give a constant Arc Lamp power. If the Arc
Lamp has not lit within 20 seconds (/LAMP_LIT still high), the System
Controller PCB will try once more to re-initiate the sequence. If the Arc Lamp
still fails to light, an error code will appear on the back panel (see section 7.22
Error Codes).
The Arc Lamp Power Supply negative output goes to the Cathode of the Arc
Lamp. The positive output goes to the Anode of the Arc Lamp and is tied to
chassis ground.
The Arc Lamp Power Supply is shielded electrically and magnetically to prevent
noise or disturbances in the CRTs or other circuitry.
Figure 3-3  
Arc Lamp Power Supply connections.
ALPS - Service Adjustments
The Arc Lamp Power Supply for the Model 250 is preset at the factory and does
not have any Service Adjustments. The output is programmed for a constant
2 kW. Arc Lamp replacement does not require any electrical readjustments.
ALPS - Remove and Replace
Tools Needed
#2 Pozi-drive Phillips-head screwdriver
Parts Needed
Arc Lamp Power Supply p/n - 105216
To remove the Arc Lamp Power Supply (ALPS):
1. Power off the projector by IR Remote or PC, and allow the cooling fans to
run until they shut off. 
						

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Model 250 Service Manual 3-9
2. Turn the AC Circuit Breaker to the OFF position and unplug the AC
Power Cord.
3. Remove the front cover (see section 6.1 Projector Covers ).
4. Remove the lower-right-side panel by removing the five Pozi-drive screws
securing it.
5. Remove the five Pozi-drive screws securing the EMI Shield. Slide the
shield to the left and remove it.
6. Disconnect the INPUT AC plug.
7. Disconnect the two CONTROL SIGNALS cables. The /LAMP_OK signal
jumper is attached to the CONTROL SIGNAL cable by a cable tie. Do not
cut this cable tie.
8. Disconnect the Arc Lamp Power Supply OUTPUT cables from the (+) and
(-) terminals. Take care not to damage the 470µ f capacitor across the
output cables. The (+) cable has a red shrink tubing on it; the (-) has a
black shrink tubing on it.
NOTE
: The capacitor on the output of the Arc Lamp Power Supply filters
transient spikes from the Arc Lamp when it arcs. Re-attach the capacitor
with the Arc Lamp output leads during reinstallation of new Arc Lamp
Power Supply.
9. Remove the 1 Pozi-drive Phillips-head screws from the bottom of the front
of the Arc Lamp Power Supply. The other screw was removed with the
EMI Shield.
10. Carefully slide the Arc Lamp Power Supply out of the projector.
11. Replace the Arc Lamp Power Supply in the reverse order.
High Voltage Power Supply  (HVPS)
HVPS - Main Functions
 The High Voltage Power Supply provides the following functions:
!
 Phase locked loop circuit for synchronization of the High Voltage Power
Supply to the HVPS_SYNC
!
 Generation of Anode voltages (25 kV) for all three CRTs (RGB)
!
 Generation of Focus voltage (G3) (7 kV) for all three CRTs (RGB)
!
 Generation of G2 (1200 V) supply voltage for the Video Amplifier PCB.
!
 Generation of G1 (-150 V) supply voltage for the Video Amplifier PCB.
!
 Dynamic Focus Amplifier using horizontal and vertical parabolas supplied to
the High Voltage Power Supply.
!
 External CRT Protection and generation of /HV_OK signal 
						

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Model 250 Service Manual
Figure 3-4  
High Voltage Power Supply I/O signals.
HVPS - Inputs
HVPS_SYNC - this signal is generated on the Raster Timing Generator PCB.
Square wave HCT level with 50 or 33% duty cycle. The signal is synchronized to
horizontal sync.
/HV_ENA - The HVPS shutdown signal from the Video Amplifier PCB
(/VA_OK).
H_PARABOLA - The horizontal parabola from the Convergence Deflection PCB
used by the Dynamic Focus Amplifier.
V_PARABOLA  - The vertical parabola from the Convergence Deflection PCB
used by the Dynamic Focus Amplifier.
± 15 V. - The power source for the analog circuitry in the High Voltage Power
Supply.
+ 80 V. - The input power for the High Voltage section of the High Voltage
Power Supply.
HVPS - Outputs
G1 Supply - goes to Video Amplifier PCB
G2 Supply - goes to Video Amplifier PCB
/HV_OK - goes to System Controller PCB 
						

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RGB Anode Voltage - goes directly to each CRT
RGB Focus Voltage - goes directly to each CRT
Arc Ground - The Arc Ground protection for each CRT from the Video Amplifier
PCB.
HVPS - Operation
The High Voltage Power Supply has three basic functions.
!
 High Voltage Generation
!
 Focus Voltages
!
 High Voltage and CRT Protection
High Voltage Generation - The High Voltage Amplifier section converts the +80
V from the Low Voltage Power Supply, to 25 kV, and divides it into three outputs
for each CRT. It also uses the HVPS_SYNC signal from the Raster Timing
Generator PCB. This signal is synchronized to the horizontal sync to eliminate
one source of moving noise on the screen. The High Voltage section also supplies
the G
2 Voltage for the Video Amplifier PCB.
Focus Voltages -  The High Voltage Power Supply receives the horizontal and
vertical parabolas from the Convergence Deflection PCB and adds them together.
They are amplified and sent to the Focus Pack section. The Focus Pack section
couples the amplified parabola waveforms to the Focus Voltages. The Focus Pack
divides the Focus Voltage into three signals and outputs each signal to a CRT.
The DC Focus Voltages are manually adjusted as necessary.
The Arc Ground signal goes to the Video Amplifier PCB and from there, connects
to the CRT. It provides a direct return path for arc currents in the event of internal
CRT arcing.
High Voltage and CRT Protection  - The High Voltage Power Supply receives a
/HV_ENA (/VA_OK) signal from the Video Amplifier PCB. This signal goes to
the Protect OR section. The Protect OR section also checks the incoming +80 V.
from the LVPS for an overcurrent condition. The Protect OR section also
monitors the high voltage output for an overvoltage condition. If any of these
checks shows a problem the Protect OR section shuts down the high voltage
amplifier. The Protect OR section outputs the /HV_OK signal telling the System
Controller PCB that the High Voltage Power Supply is functioning properly.
HVPS - Service Adjustments
Normally, the only High Voltage Power Supply adjustments are for CRT Focus.
The CRT Focus Voltage adjusts are mechanical potentiometers located on the
side of the High Voltage Power Supply (see Figure 3-5) that adjust the focus for
each CRT. The CRT Focus Voltage adjustments are detailed in the CRT Section
(see section 5.10 CRT/Yoke Assemblies). 
						

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Model 250 Service Manual
HVPS - Remove and Replace
Tools Needed
#1 Pozi-drive Phillips-head screwdriver
#2 Pozi-drive Phillips-head screwdriver
small Flathead screwdriver
Parts Needed
High Voltage Power Supply  p/n 102566
To remove the High Voltage Power Supply:
1. Power off the projector by IR Remote or PC, and allow the cooling fans to
run until they shut off.
2. Turn the AC Circuit Breaker to the OFF position and unplug the AC
Power Cord.
3. Remove the front cover.
4. Remove the High Voltage Power Supply cover (see Figure 3-5) by
removing the 1 Pozi-drive screw that secures the HVPS at the bottom of
the cover and loosening the 2 Pozi-drive screws at the top of the front flap.
Figure 3-5  
High Voltage Power Supply cover. Electronic
Focus
Adjustment 
						

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Table 3-1 
HVPS - 
P45 I/O Pinout
PIN # Description PIN # Description
1 GND (+80V) 9 +15V
2 GND (+15V) 10 -15V
3 GND (-15V) 11 G1 SUPPLY
4 GND (G1) 12 /HV_ENA
5 /HV_OK 13 V PARABOLA
6 H PARABOLA 14 H DRIVE (HVPS_SYNC
7 GND (DAF)
8 +80V
Figure 3-6  
High Voltage Power Supply.
5. Carefully slide the cover upward and outward to remove it.
NOTE
: Refer to Figure 4-5 for the remainder of this procedure.
6. Disconnect the three CRT Anode Cables.
7. Disconnect P44-G2 Out (at the middle-front of the HVPS).
8. Unsnap the cable clamp at the top of the HVPS.
9. Remove the Anode Cables and the P44 cable from the cable clamp. 
						

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10. Disconnect P45 (“Control”) at upper left of HVPS.
11. Disconnect and label the three Focus cables. The square tabs on these
cables (see Figure 3-6) may have to be lifted up. Gently pry up with a
small Flathead screwdriver.
12. Remove all the cables from the slot in the cable guide located on the left
side of the HVPS.
13. Verify that all plugs and cables are removed and out of the way so the
HVPS is free to be removed.
14. Loosen (do not remove) the two Posi-drive screws (at the bottom of the
HVPS) that secure the HVPS metal housing to the projector.
15. Remove the two Posi-drive screws that hold the top of the HVPS metal
housing to the projector frame.
16. Grasp the HVPS at the bottom and lift upward and outward so that it slides
away from the bottom screws.
17. Reinstall the High Voltage Power Supply in the reverse order.
NOTE
: When reinstalling the High Voltage Power Supply:
!
 Make sure it slides over the bottom screws and the lip at the top of the
projector frame.
!
 Make sure each anode cable “snaps” back into its receptacle. The
receptacles are about 2” inside the hole where the cable goes.
!
 Make sure the rear flap on each focus cable connector snaps over the
square socket securely. Wiggle the connector a little to make it fits
securely.
18. Replace the HVPS cover.
19. Replace the projector covers.
20. After replacing the HVPS, check and adjust Electronic Focus as necessary.