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SAFETY PRECA

SAFETY PRECAUTIONS

UTIONS

INDEX

SET 4715SET 4715SET 4715SET 4715SET 4715

MODEL 27GT716YX1 (CHASSIS CTC203AMODEL 27GT716YX1 (CHASSIS CTC203AMODEL 27GT716YX1 (CHASSIS CTC203AMODEL 27GT716YX1 (CHASSIS CTC203AMODEL 27GT716YX1 (CHASSIS CTC203A

Y1/Y7)Y1/Y7)Y1/Y7)Y1/Y7)Y1/Y7)

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Error Codes Chart .................................. 1
GridTrace Location

Main Board ..................................... 4

High Voltage Shutdown Test .................. 1

IC Functions ........................................... 1

Important Parts Information ................... 2

Miscellaneous Adjustments .................... 1

Parts List ................................................. 4

Placement Chart ..................................... 1

Safety Precautions ..................................

Schematic Component Location ............ 3

Schematic Notes ..................................... 2

Schematics

Audio ............................................... 3

PIP ................................................... 3

Power Supply .................................. 2

System Control ................................ 3

Television ........................................ 2

Test Equipment ....................................... 2
Tuner Information .................................. 1

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APRIL

APRIL 2003 SET 4715

2003 SET 4715

Model 27GT716YX1 (Chassis CTC203A

Model 27GT716YX1 (Chassis CTC203AY1/Y7)

Y1/Y7)

4715

Technical Service Data

4715

SER

SERVICE

VICE

VICE WARNING

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

VICING

VICING THE HIGH

THE HIGH

THE HIGH VVVVVOL

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GE AND CR

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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

Y RADIA

Y RADIATION AND HIGH

TION AND HIGH

TION AND HIGH VVVVVOL

OLTTTTTAAAAAGE 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

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.

SAFETY CHECKS — FIRE AND SHOCK HAZARD

Cold Leaka

Cold Leakaggggge Chec

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ks f

ks for Receiver

or Receiver

or Receivers with Isolated Gr

s with Isolated Gr

s with Isolated Ground

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 Leakaggggge Current Chec

e Current Chec

e Current Checkkkkk

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.

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.

5436 West 78th Street

Indianapolis, IN 46268-4149

Printed in the United States of America 5 4 3 2 1

03PF02087

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Schematics

hematics

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Component locations

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Representative Model

HIGH

HIGH VVVVVOL

OLTTTTTAAAAAGE SHUTDO

GE SHUTDO

GE SHUTDOWN

WN TEST

TEST

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.