GE 31GT750YX3 Technical Service Data

SAFETY PRECA SAFETY PRECA
SAFETY PRECA SAFETY PRECA SAFETY PRECAUTIONS
SERVICE SER SER VICE VICE VICE WARNING WARNING WARNING WARNING
SER SER VICE WARNING
Only qualified service technicians who are familiar with safety checks
and guidelines should perform service work. Before replacing parts,
disconnect power source to protect electrostatically sensitive parts. Do
not attempt to modify any circuit unless so recommended by the
manufacturer. When servicing the receiver, use an isolation transformer
between the line cord and power receptacle.
SER SERVICING SER SER SER VICING VICING VICING VICING THE HIGH THE HIGH V V V V V OL THE HIGH THE HIGH THE HIGH OLT T T T T A A A A A GE AND CR OL OL OL GE AND CRT T T T T GE AND CR GE AND CR GE AND CR
Use EXTREME CAUTION when servicing the high voltage circuits. To
discharge static high voltage, connect a 10K ohms resistor in series with a
test lead between the receiver ground and CRT anode lead. DO NOT lift
the CRT by the neck. Always wear shatterproof goggles when handling
the CRT to protect eyes in case of implosion.
X-RA X-RAY RADIA X-RA X-RA X-RA Y RADIA Y RADIATION AND HIGH Y RADIA Y RADIA TION AND HIGH TION AND HIGH V V V V V OL TION AND HIGH TION AND HIGH OL OL OL OLT T T T T A A A A A GE LIMITS GE LIMITS GE LIMITS GE LIMITS GE LIMITS
Be aware of the instructions and procedures covering X-ray radiation. In
solid-state receivers and monitors, the CRT is the only potential source of
X-rays. Keep an accurate high voltage meter available at all times. Check
meter calibration periodically. Whenever servicing a receiver, check the
high voltage at various brightness levels to be sure it is regulating
properly. Keep high voltage at rated value, NO HIGHER. Excessive high
voltage may cause X-ray radiation or failure of associated components.
DO NOT depend on protection circuits to keep voltage at rated value.
When troubleshooting a receiver with excessive high voltage, avoid close
contact with the CRT. DO NOT operate the receiver longer than
necessary. To locate the cause of excessive high voltage, use a variable
AC transformer to regulate voltage. In present receivers, many electrical
and mechanical components have safety related characteristics which are
not detectable by visual inspection. Such components are identified by a
# # # # # on both the schematic and the parts list. For SAFETY, use only
equivalent replacement parts when replacing these components.
GENERAL GUIDELINES GENERAL GUIDELINES GENERAL GUIDELINES GENERAL GUIDELINES GENERAL GUIDELINES
Perform a final SAFETY CHECK before returning receiver to customer.
Check repaired area for poorly soldered connections, and check entire
circuit board for solder splashes. Check board wiring for pinched wires or
wires contacting any high wattage resistors. Check that all control knobs,
shields, covers, grounds, and mounting hardware have been replaced. Be
sure to replace all insulators and restore proper lead dress.
HIGH HIGH HIGH V V V V V OL HIGH HIGH OLT T T T T A A A A A GE SHUTDO OL OL OL GE SHUTDOWN GE SHUTDO GE SHUTDO GE SHUTDO
Momentarily short BC14901 (see Q14901 base) to ground. The receiver should lose raster and sound. If
receiver does not lose raster and sound, the shutdown circuit should be repaired. To resume normal
operation, remove AC power for approximately 30 seconds and then turn the receiver on.
The listing of any available replacement part herein in no case constitutes a recommendation, warranty, or guarantee by
SAMS Technical Publishing as to the quality and suitability of such replacement part. The numbers of the listed parts have
been compiled from information furnished to SAMS Technical Publishing by the manufacturers of the specific type of
replacement part listed.
Reproduction or use, without express permission, of editorial or pictorial content, in any manner, is prohibited. No patent
liability is assumed with respect to the use of the information contained herein.
© 2003
5436 West 78th Street
Indianapolis, IN 46268-4149
Printed in the United States of America 5 4 3 2 1
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UTIONS UTIONS
UTIONS UTIONS
SAFETY CHECKS — FIRE AND SHOCK HAZARD SAFETY CHECKS — FIRE AND SHOCK HAZARD SAFETY CHECKS — FIRE AND SHOCK HAZARD
SAFETY CHECKS — FIRE AND SHOCK HAZARD SAFETY CHECKS — FIRE AND SHOCK HAZARD
Cold Leaka Cold Leaka Cold Leakag g g g g e Chec Cold Leaka Cold Leaka e Checks f e Chec e Chec e Chec ks f ks for Receiver ks f ks f or Receiver or Receivers with Isolated Gr or Receiver or Receiver s with Isolated Ground s with Isolated Gr s with Isolated Gr s with Isolated Gr ound ound ound ound
Unplug the AC cord, connect a jumper across the plug prongs, and turn
the power switch on (if applicable). Use an ohmmeter to measure the
resistance between the jumped AC plug and any exposed metal cabinet
parts such as antenna screw heads, control shafts, or handle brackets.
Exposed metal parts with a return path should measure between 1M
ohms and 5.2M ohms. Parts without a return path must measure infinity.
Hot Leaka Hot Leaka Hot Leaka Hot Leaka Hot Leakag g g g g e Current Chec e Current Check k k k k e Current Chec e Current Chec e Current Chec
Plug the AC cord directly into an AC outlet. DO NOT use an isolation
transformer. Use a 1500 ohms, 10W resistor in parallel with a .15µF
capacitor to connect between any exposed metal parts on the receiver and
a good earth ground. (See figure below.) Use an AC voltmeter with at
least 5000 ohms per volt sensitivity to measure the voltage across the
resistor. Check all exposed metal parts and measure voltage at each point.
Voltage measurements should not exceed .75VAC, 500µA. Any value
exceeding this limit constitutes a potential shock hazard and must be
corrected. If the AC plug is not polarized, reverse the AC plug and repeat
exposed metal part voltage measurement at each point.
WN WN WN TEST WN TEST TEST TEST TEST
UPC
HERE
03PF02062
Technical Service Data
INDEX INDEX INDEX
INDEX INDEX
Error Codes Chart .................................. 1
High Voltage Shutdown Test .................. 1
IC Functions ........................................... 1
Important Parts Information ................... 1
Miscellaneous Adjustments .................... 1
Parts List ................................................. 4
Placement Chart ..................................... 1
Safety Precautions .................................. 1
Schematic Component Location ............ 2
Schematic Notes ..................................... 2
Schematics
Audio ............................................... 3
Gemstar 4 ........................................ 4
PIP ................................................... 3
Power Supply .................................. 2
Television ........................................ 2
Test Equipment ....................................... 1
Tuner Information .................................. 1
For Supplier Ad For Supplier Ad For Supplier Address, dress, dress, dress,
For Supplier Ad For Supplier Ad dress,
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4702
GE GE GE GE GE
Model 31GT750YX3 (Chassis CTC203CA2) Model 31GT750YX3 (Chassis CTC203CA2) Model 31GT750YX3 (Chassis CTC203CA2) Model 31GT750YX3 (Chassis CTC203CA2) Model 31GT750YX3 (Chassis CTC203CA2)
Representative Model
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• Component locations Component locations Component locations Component locations Component locations
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MARCH 2003 MARCH MARCH MARCH MARCH 2003 2003 2003 2003 SET 4702 SET 4702 SET 4702 SET 4702 SET 4702