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SAFETY PRECA

SAFETY PRECAUTIONS

UTIONS

INDEX

SET 4733SET 4733SET 4733SET 4733SET 4733

MODEL G27648YX1 (CHASSIS CTC203AA)MODEL G27648YX1 (CHASSIS CTC203AA)MODEL G27648YX1 (CHASSIS CTC203AA)MODEL G27648YX1 (CHASSIS CTC203AA)MODEL G27648YX1 (CHASSIS CTC203AA)

RCARCARCARCARCA

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

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

High Voltage Shutdown Test .................. 1
IC Functions ........................................... 2
Important Parts Information ................... 4
Miscellaneous Adjustments .................... 1
Parts List ................................................. 4
Placement Chart ..................................... 1
Safety Precautions .................................. 1
Schematic Component Location ............ 3
Schematic Notes ..................................... 2
Schematics

Audio ............................................... 3
Comb Filter ..................................... 3
Gemstar 4 ........................................ 3
Power Supply .................................. 2
Television ........................................ 2

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

For Supplier Ad

For Supplier Address,

dress,

See PHO

See PHOT

TOF

OFA

ACT Ann

CT Ann

CT Annual Inde

ual Inde

ual Index

JUNE

JUNE 2003 SET 4733

2003 SET 4733

RCA

Model G27648YX1 (Chassis CTC203AA)

4733

Technical Service Data

4733

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 V

VOL

OLT

AGE AND CR

GE AND CR

GE AND CRT

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 V

VOL

OLT

AGE 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 Leakag

ge Chec

e Chec

e Checks f

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 Leakag

ge Current Chec

e Current Chec

e Current Check

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.

9850 East 30th Street
Indianapolis, IN 46229

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

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SET 4733

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4733

•

Schematics

hematics

• Component locations

Component locations

•

Par

arts list

ts list

Essential co

Essential covera

vera

verag

fffffor ser

or ser

or servicing a tele

vicing a tele

vicing a television receiver

vision receiver

vision receiver...

...

Coverage includes these additional models and chassis:

Models

Chassis

G27648YX51

CTC203AA5

G27648YX51

CTC203AA9

G27648YX52

CTC203AA5

G27648YX52

CTC203AA9

Representative Model

HIGH

HIGH V

VOL

OLT

AGE 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.