BELINEA 10 55 70 Manuale utente

Notes

Belinea

55 70 Service Manual

Preface

Before You Start

General Safety Precautions

Use an isolation transformer in

the

power line and AC

supply to troubleshoot.

When servicing, observe the original lead dress, espe-

cially in the high voltage circuits. If a short circuit is

found, replace all parts which have been overheated or

damaged.

Before turing the display on, measure the resistance

between B+ line and chassis ground. Connect the nega-

tive side of an ohmmeter to the B+ lines and the positive

side to chassis ground. Each line should have more

resisstance

than the following specifications:

B+ Line Minimum Resistance

+2oov

119.5am

+75v

a.77m

Potentials, as high as

25kV

are present when this display

is in operation. Operation of the display without the rear

cover involves the danger of a shock hazard from the

display power supply. Servicing should not be at-

tempted by anyone who is not thoroughly familiar with

the precautions necessary when working on high volt-

age equipment. Always discharge the anode of the pic-

ture tube to the display chassis before handling the tube.

After servicing, be sure to check the items listed in the

Safety Checkout, below before returning the serviced

unit to the customer.

Safety Checkout

The following checks must be made after correcting

the

original service problem and before the unit is returned to the

customer.

Check the area of your repair for unsoldered or poorly

soldered connections. Check the entire board surface for

solder splashes and bridges.

Check the inter board wiring to ensure that no wires are

pinched or coated

with

high-wattage resistors.

Check that all control knobs, shields, covers, ground

straps and mounting hardware have been replaced.

Makde absolutely sure you have replaced all the

insula-

t0l-S.

Look for any unauthorized replacement parts, particu-

larly transistors, that may have been installed dueing a

previous repair. Point

them

out to the

cusstomer

land

recommend their replacement.

Look for parts which, though functioning, show obvious

signs of deterioration. Point them out to the customer

and recommend their replacement.

Check the line cord for

cracks

and abrasion. Recom-

mend the replacement of any such line cord to the

customer.

After making any repair, check the B+ and HV to see

whether they are at the values specified. Make sure your

instruments are accurate; if your HV meter always

shows a low HV, check the meter

ensure it is not

malfunctioning.

Carry out the leakage current checks as detailed below

overleaf.

Leakage Current Cold Check

Unplug the AC cord and connect a jumper between the

two prongs on the plug.

2. Turn on the display power switch.

Use an ohmmeter to measure

the

resistance value

bc-

twcen

the

jumpered

AC plug and

each

exposed metallic

cabint part on the display, such as screwheads, terminals

control shafts.

etc.

When

exposed

metallic

part has a

return path to the chassis, the reading should be bctwccn

240k and

5.2M.

When exposed metal does not

have

return

path

the chassis,

the

reading must be.

Leakage Current Hot Check How to Find A Good Earth

Plug the AC cord into the AC outlet. Do not use an

isolation transformer for this check.

2. Connect a

1.5k,

10 watt resistor in parallel with a 0.15F

capacitor between each exposed metallic part on the set

and a good earth ground (see How to Find a Good Earth,

below) as shown in the diagram below.

A cold water pipe is a guaranteed earth ground; the cover plate

retaining screw on most AC outlet boxes is also at earth

ground. If the retaining screw is to be used as your earth

ground, verify that it is at ground by measuring the resistance

between it and a cold water pipe with an ohmmeter. The

reading should be zero (0) ohms. If a cold water pipe is not

accessible, connect a 60-100 watt trouble light (not a neon

lamp) between the hot side of an AC power receptacle and the

retaining screw. Try both slots, if necessary, to locate the hot

side of the line. The lamp should light at

normal

brilliance if

the screw is at ground potential

Leakage Current Hot-Chedc Circuit

VOLTMETER

Example of Leakage Current Hot-Check Circuit

Use an AC voltmeter with 1000 ohms/volt or more

sensitivity to measure the potential across the resistor.

Check each exposed metallic part, and measure the

voltage at each point.

Reverse the polarity of the AC plug in the AC outlet and

repeat the above measurements.

The potential at any point should not exceed 0.75 volt

RMS. A leakage current tester (Simpson Model 229,

RCA WT-540A or equivalent) may be used to make the

hot checks.

Trouble light

Cold water

pipe

How to Check for Earth Ground

Leakage current must not exceed 0.5 milliarnp. If a measure-

ment is outside of the specified limit, there is a possibility of

a shock hazard and the monitor should be repaired and re-

checked before it is returned to the customer.

Disassembly Instructions

PaH

VA Version

2.1.

Removing the Rear Cover. . . . . . . . . . . . . . . . . . . . .

2-1

2.2.

internal Disassembly (Right Side). . . . . . . . . . . . . . .

2-l

2.3.

Internal Disassembly (Left Side). . . . . . . . . . . . . . .

2-l

2.4.

Removing the Neck Board and Main Board . . . . . . .

2-2

2.5.

Removing the Control Board. . . . . . . . . . . . . . . . . . .

2-2

Part 2. Non-VA Version

2.6.

Removing the Rear Cover. .................... 2-3

2.7.

Internal Disassembly (Right Side). ..............

2-3

2.8.

Internal Disassembly (Left Side). ...............

2-3

2.9.

Removing the Neck Board and Main Board ....... 2-4

2.10.

Removing the Control Board. .................. 2-4

VA Version

2.1. Removing the Rear Cover

Turn the display so it is resting face downwards on the

work surface. Be sure to place a cloth or other soft

material on the work surface to avoid scratching the

screen surface.

Remove the four screws at the rear of the display. Refer

to the figure 2-l (A).

Remove the rear cover.

Figure

2-1

Remove the Rear Cover

2.2. Internal Disassembly (Right Side)

The neck board is plugged on to the CRT neck and is enclosed

in a metal shielding.

Disconnect the two ground wires from the Neck Shield.

Refer to the figure 2-2 (A).

Figure 2-2

internal

Disassembly (Right Side)

Remove the connected pin from the Neck Board. Refer

to the figure 2-2 (B).

Remove the screw at the rear chassis. Refer to the figure

2-2 (C).

4. Cut the two cable ties indicated to free the cables. Refer

to the figure 2-2 (D).

Disconnect the degaussing coil from the Main Board.

Refer to the figure 2-2

Release the cable wire indicated to free the cables. Refer

to the figure 2-2

(F).

Remove the nylon revets holding from Bezel. Refer to

the figure 2-2 (G).

2.3. Internal Disassembly (Left Side)

Cut the four cable ties indicated to free the cables. Refer

to the figure 2-3 (A).

2. Disconnect the three ground wires from the Neck

Shield. Refer to the figure 2-3 (B).

Remove the screw at the FBT cover. Refer to the figure

2-3 (C).

Remove the nylon revets holding from fix plate. Refer

to the figure 2-3 (D).

Remove the connected pin from the Logic Board. Refer

to the figure 2-3 (E).

6. Remove Logic Board.

Remove the connected pin from the Connector Board.

Refer to the figure 2-3

(F).

Remove the two connected pins from the Main Board.

Refer to the figure 2-3 (G).

Figure 2-3 Internal Disassembly (Left side)

2-l

To avoid risk of electric shock, before

re-

moving the anode cap, made sure tdhe

ode has been completely discharged as

high voltage may remain on the anode for

extended time after power off.

Remove the anode cap from the CRT. Refer to the figure

2-3

(H).

10. Remove the nylon revets holding from Bezel. Refer to

the figure 2-3 (I).

2.4. Removing the Neck Board

Main Board

Remove the screw from

Bracket. Refer to the figure

2-4

(A).

figure

2-4 Remove the Control Panel

Figure

Z-5

Remove the Neck Board and Main

Board

2Remove the two Lock Caps from the

nylon ties.

Refer to

the figure 2-5 (A).

Remove the two ground wires from the Neck Shield.

Refer to the figure 2-5 (B).

Remove the Neck Shield.

Remove Neck Board.

Remove the Main Board.

2.5.

Remove the Control Board

Remove the two screws from Control Panel. Refer to

the figure

2-4 (B).

Remove the Control Panel.

Remove the six screws from the Control

Board.

Refer

to the figure 2-6 (A).

Remove the Control Board.

Figure Z-6

Remove

the

Control

Board

2-2

UPart

con-VA

Version

2.6.

Removing the Rear Cover

Remove the four screws at the rear of the display, and

lift the cover vertically away from the monitor. Refer to

the figure 2-7

(A).

2. 1

Xemove the rear cover.

Figure 2-7 Remove the Rear Cover

2.7. Internal Disassembly

(Right Side)

The neck board is plugged on to the CRT neck and is enclosed

in a metal shielding.

Disconnect the ground wires from the metal casing of

the neck board. Refer to the figure 2-8 (A).

Figure 2-8 Internal Disassembly (Right Side)

2.8.

Internal Disassembly (Left Side)

Disconnect the ground wires from the metal

casing

of’

the neck board. Refer to the figure 2-9 (A).

Remove the two screws from the

PBT

cover and U

bracket. Refer to the figure 2-9 (B).

Rmove the ground pin from the neck board. Refer to the

figure 2-9 (C).

Cut the cable tie indicated to free the cables. Refer to the

figure 2-9

0).

Remove the nylon revets holding from Bezel. Refer to

the figure 2-9 (E).

Disconnect the ribbon cable from the Logic Board and

the cable from the CRT connected to the rear side of the

logic board. Refer to the figure 2-9

(P).

Remove the Logic Board.

Remove the connected pin from the Connector Board.

Refer to the figure 2-9 (G).

Remove the connected pin from

the

Main Board. Refer

to the figure 2-9 (H).

Disconnect the degaussing coil from the main board.

Refer to the figure 2-8 (B).

Removing the screw from the chassis mat. Refer to the

figure 2-8 (C).

Place the display flat on

its

face and remove the nylon

revets holding the main board in place on the frame.

Refer to the figure 2-8 (D).

10. Remove the connected from Main Board, and the con-

nected from Main Board to Earphone Board.. Refer to

the figure 2-9 (I).

To avoid risk

electric shock, before re-

moving the anode cap, made sure tdhe an-

ode has been completely discharged as

high voltage may remain on the anode for

extended time after power off.

Figure 2-9 Internal Disassembly (Lift Side)

2-3

I-

11.

Remove the CRT anode cap. Refer

to the figure 2-9

(J).

12. Place the diiplay flat on its face and remove the nylon

revets

holding the main board in place on the frame.

Refer to the figure 2-9 (K).

2.9.

Removing the Neck

Board and

Main Board

1. Disconnect the three ground wires from the metal casing

of the neck board. Refer to the figure 2-10 (A).

Remove the two

Lock

Caps from the nylon ties. Refer

to the figure 2-10 (B).

Remove the Neck Board from the CRT.

Remove the Main Board.

Figure

Z-10

Removing the Main Board

2.10. Removing the Control PCB

Remove the

two

screws from Backet Cover. Refer to the

figure 2- 10 (C).

Remove the seven screws from Control Panel. Refer to

the figure 2-11 (A).

Remove

the Control Board.

Figure

2-11

Removing the Control PCB

2-4

Notes

2-5

Indice

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