GDM-400PS, GDM-400PST - Sony Monitor Service Manual (repair manual). Page 2

Read Sony GDM-400PS / GDM-400PST Service Manual online

N-3 17inch
GDM-400PS/400PST
– 2 –
SAFETY  CHECK-OUT
(US Model only)
After correcting the original service problem, perform the
following safety checks before releasing the set to the customer:
1.
Check the area of your repair for unsoldered or poorly-sol-
dered connections. Check the entire board surface for solder
splashes and bridges.
2.
Check the interboard wiring to ensure that no wires are
“pinched” or contact high-wattage resistors.
3.
Check that all control knobs, shields, covers, ground straps,
and mounting hardware have been replaced. Be absolutely
certain that you have replaced all the insulators.
4.
Look for unauthorized replacement parts, particularly tran-
sistors, that were installed during a previous repair. Point
them out to the customer and recommend their replacement.
5.
Look for parts which, though functioning, show obvious
signs of deterioration. Point them out to the customer and
recommend their replacement.
6.
Check the line cords for cracks and abrasion. Recommend
the replacement of any such line cord to the customer.
7.
Check the B+ and HV to see if they are specified values.
Make sure your instruments are accurate; be suspicious of
your HV meter if sets always have low HV.
8.
Check the antenna terminals, metal trim, “metallized”
knobs, screws, and all other exposed metal parts for AC
Leakage. Check leakage as described below.
3.
Measuring the voltage drop across a resistor by means of a
VOM or battery-operated AC voltmeter. The “limit” indica-
tion is 0.75 V, so analog meters must have an accurate low-
voltage scale. The Simpson 250 and Sanwa SH-63Trd are
examples of a passive VOMs that are suitable. Nearly all
battery operated digital multimeters that have a 2 V AC
range are suitable.  (See Fig. A)
WARNING!!
NEVER TURN ON THE POWER IN A CONDITION IN
WHICH THE DEGAUSS COIL HAS BEEN REMOVED.
SAFETY-RELATED COMPONENT WARNING!!
COMPONENTS IDENTIFIED BY SHADING AND MARK 
¡
ON THE SCHEMATIC DIAGRAMS, EXPLODED VIEWS
AND IN THE PARTS LIST ARE CRITICAL FOR SAFE
OPERATION. REPLACE THESE COMPONENTS WITH
SONY PARTS WHOSE PART NUMBERS APPEAR AS
SHOWN IN THIS MANUAL OR IN SUPPLEMENTS
PUBLISHED BY SONY. CIRCUIT ADJUSTMENTS THAT
ARE CRITICAL FOR SAFE OPERATION ARE IDENTIFIED
IN THIS MANUAL. FOLLOW THESE PROCEDURES
WHENEVER CRITICAL COMPONENTS ARE REPLACED
OR IMPROPER OPERATION IS SUSPECTED.
AVERTISSEMENT!!
NE JAMAIS METTRE SOUS TENSION QUAND LA
BOBINE DE DEMAGNETISATION EST ENLEVÉE.
ATTENTION AUX COMPOSANTS RELATIFS À LA
SÉCURITÉ!!
LES COMPOSANTS IDENTIFIÉS PAR UNE TRAME ET
UNE MARQUE 
¡
 SONT CRITIQUES POUR LA
SÉCURITÉ.  NE LES REMPLACER QUE PAR UNE PIÈCE
PORTANT LE NUMÉRO SPECIFIÉ.  LES RÉGLAGES DE
CIRCUIT DONT L’IMPORTANCE EST CRITIQUE POUR
LA SÉCURITÉ DU FONCTIONNEMENT SONT
IDENTIFIÉS DANS LE PRÉSENT MANUEL.  SUIVRE CES
PROCÉDURES LORS DE CHAQUE REMPLACEMENT  DE
COMPOSANTS CRITIQUES, OU LORSQU’UN MAUVAIS
FONCTIONNE-MENT EST SUSPECTÉ.
CAUTION  ON  DAS  (ECS)  CONNECTOR
•
The connector for DAS (ECS) adjustment is provided inside
the cover shown below. Be careful with an electrical shock
when connecting the connector with the power supplied. Also,
return the removed cover to the home position.
1.5 k W
0.15 µF
AC
Voltmeter
(0.75 V)
To Exposed Metal
Parts on Set
Earth Ground
Fig. A. Using an AC voltmeter to check AC leakage.
LEAKAGE  TEST
The AC leakage from any exposed metal part to earth ground
and from all exposed metal parts to any exposed metal part having a
return to chassis, must not exceed 0.5 mA (500 microampers).
Leakage current can be measured by any one of three methods.
1.
A commercial leakage tester, such as the Simpson 229 or
RCA WT-540A. Follow the manufacturers’ instructions to
use these instruments.
2.
A battery-operated AC milliammeter. The Data Precision
245 digital multimeter is suitable for this job.
Left side
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