SR25-3828VD0171B
3-1
CL - SERVICING
SERVICING
GENERAL INFORMATION
Servicing the CL chassis is the same as with other Zenith
single-board chassis. If the set is dead, first check the
standby and switched voltages. If the switched voltages
do not appear, check the power “On” circuit. If the power
supply is OK and the set will turn on, the Horizontal
sweep circuit should be checked next. Is horizontal drive
available from the video processor chip? If the sweep
system does not start up, sweep-derived voltages will
not be generated.
If the sweep and high-voltage circuits are OK and video
or audio are missing, then the audio/video/tuner
circuits should be checked. If the receiver is working
but some feature is not working, check the Service Menu.
Bring up the Service menu and check to be sure that all
items are set correctly.
MODULE-LEVEL SERVICING
The CL Chassis is Module Level repair only. Replacement
modules are available on an exchange basis.
If the CRT or Video processor IC are replaced, Black/
White tracking must be reset. Refer to the Service Menus
section of this book for Black/White tracking
adjustments.
When troubleshooting video circuits, remember that all
video travels through the Video/Audio switcher IC. A
defect in either of these IC’s can result in no video.
WARNING!
DO NOT disconnect the Video output module
from the CRT when troubleshooting 32” receiv-
ers. If the video output module is removed on
these sets while power is ON, the CRT will arc
and can be permanently damaged. Also, the
technician is in danger of serious shock. There is
a termination circuit (W5101) on the CRT mod-
ule to prevent this from happening.
SERVICING THE POWER SUPPLY
Check the standby voltages first:
+VM at CX3415 (usually 169.7 VDC when 120 VCA)
B+ at CX3801
Note: B+ 124 VDC for 32” & 27”, B+ 126 VDC for
25” and B+ 120 VDC for 19” & 20”.
+12 VSB at CX3613
+14 at CX3610
+5 VSB at CX3841
Check the following:
Keyboard input at IC6000 pins 7 and 8
IR input at IC6000 pin 15
Power On output at IC6000 pin 32
Check the switched voltages:
+9 VSW DC at CX3811
+14 VAUD DC for the Audio Amp at 2X3510
+8 VSW DC CX3831
SWEEP DERIVED VOLTAGES
+28 volts DC at (+) CX2114
+35 volts DC at the junction of CX3253 and DX3252
+215 volts DC at the junction of CX3208 and RX3208
+33 volts DC at the junction of RX3216 and ZD6001
CRT FILAMENT
Check at pin 3 and 4 of connector CN2C5A. This should
read voltages between 6.0 and 6.4 volts AC on a true
RMS meter.
VIDEO PROCESSOR ICX2200
Check the following key operating signals and voltages:
Luminance at ICX2200 pin 43
Chroma at ICX2200 pin 45
Horizontal drive at pin 32
Vertical drive at pin 24
R Out pin 19
G Out pin 20
B Out pin 21
Serial Clock, Serial Data pins 27 and 28 respectively
VCC 9 volts pins 9, 26, 46 & 48
R in from micro (IC6000) at pin 15
G in from micro (IC6000) at pin 16
B in from micro (IC6000) at pin 17
Summary of Contents for H19F34DT Series
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