Magnum PF21GB300, PF21500, PF21516S Service Manual

李 庆亮 10-11-19, 15:05

COLOR TELEVISION

SERVICE MANUAL

MODELNO: PF21GB300

PF21500

PF21516S

CHASSIS NO. ETE-3

Please read this manual carefully before service.

1. SAFETY INSTRUCTIONS AND MAINTENANCE
WARNING: BEFORE SERVICING THIS CHASSIS, READ THE “X-RAY RADIATION

PRECAUTION”, “SAFETY PRECAUTION”AND “PRODUCT SAFETY

NOTICE”INSTRUCTION BELOW.

1.1 X-RAY RADIATION PRECAUTION

1.1.1 The EHT must be checked every time the TV is serviced to ensure that the CRT does not emit X-ray

radiation as result of excessive EHT voltage. The maximum EHT voltage permissible in any operating
circumstances must not exceed the rated value. When checking the EHT, use the High Voltage Check
procedure in this manual using an accurate EHT voltmeter.

1.1.2 The only source of X-RAY radiation in this TV is the CRT. The TV minimizes X-RAY radiation, which

ensures safety during normal operation. To prevent X-ray radiation, the replacement CRT must be identical to
the original fitted as specified in the parts list.

1.1.3 Some components used in this TV have safety related characteristics preventing the CRT from emitting

X-ray radiation. For continued safety, replacement component should be made after referring the PRODUCT
SAFETY NOTICE below.

1.1.4 Service and adjustment of the TV may result in changes in the nominal EHT voltage of the CRT anode.

So ensure that the maximum EHT voltage does not exceed the rated value after service and adjustment.

1.2 SAFETY PRECAUTION

WARNING: REFER SERVICING TO QUALIFIED SERVICE PERSONNEL ONLY.

1.2.1 The TV has a nominal working EHT voltage. Extreme caution should be exercised when working on the

TV with the back removed.

Do not attempt to service this TV if you are not conversant with the precautions and procedures for

working on high voltage equipment.

When handling or working on the CRT, always discharge the anode to the TV chassis before removing the

anode cap in case of electric shock.

The CRT, if broken, will violently expel glass fragments. Use shatterproof goggles and take extreme care

while handling.

Do not hold the CRT by the neck as this is a very dangerous practice..

1.2.2 It is essential that to maintain the safety of the customer all power cord forms be replaced exactly as

supplied from factory.

1.2.3 Voltage exists between the hot and cold ground when the TV is in operation. Install a suitable isolating

transformer of beyond rated overall power when servicing or connecting any test equipment for the sake of
safety.

1.2.4 When replacing ICs, use specific tools or a static-proof electric iron with small power (below 3 5W).

1.2.5 Do not use a magnetized screwdriver when tightening or loosing the deflection yoke assembly to avoid

electronic gun magnetized and decrement in convergence of the CRT.

1.2.6 When remounting the TV chassis, ensure that all guard devices, such as nonmetal control buttons, switch,

insulating sleeve, shielding cover, isolating resistors and capacitors, are installed on the original place.

1.2.7 Replace blown fuses within the TV with the fuse specified in the parts list.

1.2.8 When replacing wires or components to terminals or tags, wind the leads around the terminal before

soldering. When replacing safety components identified by the international hazard symbols on the
circuit diagram and parts list, it must be the company-approved type and must be mounted as the original.

1.2.9 Keep wires away from high temperature components.

1.3 PRODUCT SAFETY NOTICE

CAUTION: FOR YOUR PROTECTION, THE FOLLOWING PRODUCT SAFETY NOTICE

SHOULD BE READ CAREFULLY BEFORE OPERATING AND SERVICING THIS TV SET.

1.3.1 Many electrical and mechanical components in this chassis have special safety-related characteristics.

These characteristics are often passed unnoticed by a visual inspection and the X-ray radiation protection
afforded by them cannot necessarily be obtained by using replacements rated at higher voltages or wattage, etc.
Components which have these special safety characteristics in this manual and its supplements are identified by
the international hazard symbols on the circuit diagram and parts list. Before replacing any of these
components read the parts list in this manual carefully. Substitute replacement components which do not have
the same safety characteristics as specified in the parts list may create X-ray radiation.

1.3.2 Do not slap or beat the cabinet or CRT, since this may result in fire or explosion.

1.3.3 Never allow the TV sharing a plug or socket with other large-power equipment. Doing so may result in

too large load, causing fire.

1.3.4 Do not allow anything to rest on or roll over the power cord. Protect the power cord from being walked

on, modified, cut or pinched, particularly at plugs.

1.3.5 Do not place any objects, especially heavy objects and lightings, on top of the TV set. Do not install th e TV

near any heat sources such as radiators, heat registers, stove, or other apparatus that produce heat.

1.3.6 Service personnel should observe the SAFETY INSTRUCTIONS in this manual during use and servicing

of this TV set. Otherwise, the resulted damage is not protected by the manufacturer.

1.4 SAFETY SYMBOL DESCRIPTION

The lightning symbol in the triangle tells you that the voltage inside this product may be strong nough to

cause an electric shock. Extreme caution should be exercised when working on the TV with the back removed.

This is an international hazard symbol, telling you that the components identified by the symbol have

special safety-related characteristics.
UL This symbol tells you that the critical components identified by the UL marking have special safety-related
characteristics.
VDE or TUV This symbol tells you that the critical components identified by the VDE/TUV marking have

special safety-related characteristics.

1.5 MAINTENANCE

1.5.1 Place the TV set on a stable stand or base that is of adequate size and strength to prevent it from

being accidentally tipped over, pushed off, or pulled off. Do not place the set near or over a radiator or
heat register,

or where it is exposed to direct sunlight.

1.5.2 Do not install the TV set in a place exposed to rain, water, excessive dust, mechanical vibrations or

impacts.

1.5.3 Allow enough space (at least 10cm) between the TV and wall or enclosures for proper ventilation.

1.5.4 Slots and openings in the cabinet should never be blocked by clothes or other objects.

1.5.5 Please power off the TV set and disconnect it fro m the wall immediately if any abnormal condition are

met, such as bad smell, belching smoke, sparkling, abnormal sound, no picture/sound/raster. Hold the plug
firmly when disconnecting the power cord.

1.5.6 Unplug the TV set from the wall outlet before cleaning or polishing it. Use a dry soft cloth for cleaning

the exterior of the TV set or CRT screen. Do not use liquid cleaners or aerosol cleaners.

2. ADJUSTMENTS

2.1 SET-UP ADJUSTMENTS

The following adjustments should be made when a complete realignment is required or a new picture tube is
installed.
Perform the adjustments in the following order:
Color purity
Convergence
White balance

Notes:

The purity/convergence magnet assembly and rubber wedges need mechanical positioning.

For some picture tubes, purity/ convergence adjustments are not required.

2.1.1 Color Purity Adjustment

Preparation:

Before starting this adjustment, adjust the vertical sync, horizontal sync, vertical amplitude and focus.

•Face the TV set north or south.

•Connect the power plug into the wall outlet and tu rn on the main power switch o f the TV set. •O pe r ate th e

TV for at least 15 minutes.

•Degauss the TV set using a specific degaussing coil.

•Set the brightness and contrast to maximum.

•Counter clockwise rotate the R /B low brightness potentiometers to the end and rotate the green low brightness

potentiometer to center.

•Receive green raster pattern signals.

•Loosen the clamp screw holding the deflection yoke assembly and slide it forward or backward to display a

vertical green zone on the screen. Rotate and spread the tabs of the purity magnet around the neck of the CRT
until the green zone is located vertically at the center of the screen. •Slo wly move the deflection yo ke assembly
forward or backward until a uniform green screen is obtained.

•Tighten the clamp screw of the assembly temporarily. Check purity of the red raster and blue raster un til

purities of the three rasters meet the requirement.

2.1.2 Convergence Adjustment

Preparation: Before attempting any convergence adjustment, the TV should be operated for at least 15

minutes.

•Center convergence adjustment.

•Receive dot pattern.

•Adjust the brightness/contrast controls to obtain a sharp picture.

•Adjust two tabs of the 4-pole magnet to change the angle between them and red and blue vertical lines are

superimposed each other on the center of the screen.

•Turn both tabs at the same time keeping the angle constant to superimpose red and blue horizontal on the

center of the screen.

•Adjust two tabs of the 6-pole magnet to superimpose red/blue line and green line.

•Remember red and blue movement. Repeat steps 2.1.3 2. 1.5 until optimal convergence is obtained.

•Circumference convergence adjustment.

•Loosen the clamp screw holding the deflection yoke assembly and allow it tilting .

•Temporarily put the first wedge between the picture tube and deflection yoke assembly. Move front of the

deflection yoke up or down to obtain better convergence in circumference. Push the mounted wedge in to fix
the yoke temporarily.

•Put the second wedge into bottom.

•Move front of the deflection yoke to the left or right to obtain better convergence in circumference.

•Fix the deflection yoke position and put the third wedge in either upper space. Fasten the deflection yoke

assembly on the picture tube.

•Detach the temporarily mounted wedge and put it in either upper space. Fasten the deflection yoke assembly

on the picture tube.

•After fastening the three wedges, recheck overall convergence and ensure to get optimal convergence. Tighten

the lamp screw holding the deflection yoke assembly.

2.1.3 White Balance Adjustment

Generally, white balance adjustment is made with professional equipment. It’s not practical to get good white
balance only through manual adjustment. For TVs with I2C bus control, change the bus data to adjust white
balance.

2.2 CIRCUIT ADJUSTMENTS

Preparation:

Circuit adjustments should be made only after completion of set-up adjustments.
Circuit adjustments can be performed using the adjustable components inside the TV set. For TVs with 2 I C
bus control, first change the bus data.

2.2.1 Degaussing

A degaussing coil is built inside the TV set. Each time the TV is powered on, th e degaussing coil

will automatically degauss the TV. If the TV is magnetized by external strong magnetic field, causing color
spot on the screen, use a specific degausser to demagnetize the TV in the following ways. Otherwise, color
distortion will be shown on the screen.

•Power on the TV set and operate it for at least 15 minutes.

•Receive red full-field pattern.