Dell D1626HT - UltraScan 1600HS - 21" CRT Display Manuale di servizio - Pagina 2

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D1626HT

After correcting the original service problem, perform the fol-

lowing 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 transis-

tors, 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 recom-

mend 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.

0.15 F

Fig. A. Using an AC voltmeter to check AC leakage.

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.

SAFETY CHECK-OUT

To Exposed Metal

Parts on Set

1.5 k

Voltmeter

(0.75 V)

Earth Ground

Rear side

(US Model only)

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 meth-

ods.

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.

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 ex-

amples of a passive VOMs that are suitable. Nearly all battery

operated digital multimeters that have a 2 V AC range are suit-

able. (See Fig. A)

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 AP-

PEAR AS SHOWN IN THIS MANUAL OR IN SUPPLE-

MENTS PUBLISHED BY SONY. CIRCUIT ADJUST-

MENTS THAT ARE CRITICAL FOR SAFE OPERATION

ARE IDENTIFIED IN THIS MANUAL. FOLLOW THESE

PROCEDURES WHENEVER CRITICAL COMPO-

NENTS ARE REPLACED OR IMPROPER OPERATION

IS SUSPECTED.

NE JAMAIS METTRE SOUS TENSION QUAND LA

BOBINE DE DEMAGNETISATION EST ENLEVÉE.

ATTENTION AUX COMPOSANTS RELATIFS À LA

LES COMPOSANTS IDENTIFIÉS PAR UNE TRAME ET

UNE MARQUE

SÉCURITÉ. NE LES REMPLACER QUE PAR UNE PIÈCE

PORTANT LE NUMÉRO SPECIFIÉ. LES RÉGLAGES DE

CIRCUIT DONT L'IMPORTANCE EST CRITIQUE POUR

SÉCURITÉ

IDENTIFIÉS DANS LE PRÉSENT MANUEL. SUIVRE CES

PROCÉDURES LORS DE CHAQUE REMPLACEMENT

DE COMPOSANTS CRITIQUES, OU LORSQU'UN

MAUVAIS FONCTIONNE-MENT EST SUSPECTÉ.

– 2 –

WARNING!!

AVERTISSEMENT!!

SÉCURITÉ!!

SONT CRITIQUES POUR LA

FONCTIONNEMENT

SONT