Panasonic TC-20B12, TC-14A12P service manual Contents, General Guidelines

TC-14A12P / TC-20B12

WARNING

This service information is designed for experienced repair technicians only and is not designed for use by the general public. It does not contain warnings or cautions to advise non-technician individuals of potential dangers in attempting to service a product. Products powered by electricity should be serviced or repared only by experienced professional technicians.

Any attempt to service or repair the product deal with in this service information by anyone could result in serious injury or death.

Contents General Guidelines

General Guidelines	02
Operation Guide	03
IC 601 - Pins and Functions	15
IC601 and IC451 Voltage Table	17
IC601 - Block Diagram	18
General Summary	19
Service Adjustments and Calibrations
Service Mode	20
How to operate the DAC controls	20
EQUIPMENT REQUIRED	21
AGC RF CALIBRATION	21
BUZZ (SOUND CIRCUIT)	21
ANODE AND HEATER VOLTAGE CONFIRMATION	21
PAL COLOR OUTPUT SIGNAL ADJUSTMENT	21
NTSC SUB-TINT CALIBRATION	22
PROTECTION CIRCUIT (SHUTDOWN)	22
CONFIRMATION OF OPERATION	22
WHITE QUALITY CALIBRATION	22
VERTICAL DEFLECTION	22
CALIBRATION AND CONFIRMATION	22
CRT CUT OFF CALIBRATION	23
WHITE BALANCE CALIBRATION	23
SUB-BRIGHTNESS CALIBRATION	23
FOCUS CALIBRATION	23
COLOR PURITY ADJUSTMENT	24
CONVERGENCE CALIBRATION	24
EEPROM - Memory Maps	25
Power Source Voltages	25
Main Board Schematic Diagram	26
CRT Board Schematic Diagram	27
Main Board Conductor view	28
Waveform	32
Parts Location	35
Packing and Acessories	36
Replacement Mechanical Parts List	36
Replacement Electrical Parts List	37

An Isolation Transformer should always be used during the servicing of a receiver whose chassis is not isolated from the AC power line. Use a transformer of adequate power rating as this protects the technician from accidents resulting in personal injury from electrical shocks. It will also protect the Receiver from being damaged by accidental shorting that may occur during servicing. When servicing, observe the original lead dress, especially in the high voltage circuit. Replace all damaged parts (also parts that show signs of overheating.)

Always Replace Protective Devices, such as fishpaper, isolation resistors and capacitors, and shields after servicing the Receiver. Use only manufacturer’s recommended rating for fuses, circuit breakers, etc.

High potentials are present when this Receiver is operating. Operation of the Receiver without the rear cover introduces danger from electrical shock. Servicing should not be performed by anyone who is not thoroughly familiar with the necessary precautions when servicing high-voltage equipment.

Extreme care should be practiced when Handling the Picture Tube. Rough handling may cause it to implode due to atmospheric pressure (14.7 lbs per sq. in). Do not sick or scratch the glass or subject it to any undue pressure. When handling, use safety goggles and heavy gloves for protection. Discharge the picture tube by shorting the anode to chassis ground (not to the cabinet or to other mounting hardware). When discharging, connect cold ground (i.e. dag ground lead) to the anode with a well insulated wire or use a grounding probe.

Avoid prolonged exposure at close range to unshielded areas of the picture tube to prevent exposure to X-ray radiation.

The Test Picture Tube used for servicing the chassis at the bench should incorporate safety glass and magnetic shielding. The safety glass provides shieldinf for the tube viewing area against X-ray radiation as well as implosion. The magnetic shield limits X-ray radiation around the bell of the picture tube in addition to restricting magnetic effects. When using a picture tube test jig for service, ensure that the jig is capable of handling 31kV without causing X-ray radiation.

Before returning a serviced receiver to the owner, the service technician must thoroughly test the unit to ensure that is completely safe to operatore. Do not use a line isolation transformer when testing.

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