Panasonic CT-26WX15UN Panduan Servis - Halaman 3

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Put the iron wire under the pins of the Flat IC and pull it in the direction indicated while heating the pins using a soldering iron. A small awl can be used instead of the iron wire.

Remove the solder from all the pads of the Flat IC by using a de solder braid

Position the new Flat IC in place (apply the pins of the Flat IC to the soldering pads where the pins need to be soldered). Properly determine the positions of the soldering pads and

pins by correctly aligning the polarity symbol

Solder all pins to the soldering pads using a fine tipped soldering iron

Check with a magnifier for solder bridge between the pins or for dry joint between pins and soldering pads. To remove a solder bridge, use a de solder braid as shown in the figure

below

IMPORTANT

To protect against possible damage to the solid state devices due to arching or static discharge, make certain that all ground wires and CRT DAG wire are securely connected.

CAUTION

The power supply circuit is above earth ground and the chassis cannot be polarized. Use an isolation transformer when servicing the receiver to avoid damage to the test equipment or to

the chassis. Connect the test equipment to the proper ground (hot) or (cold) when servicing, or incorrect voltages will be measured.

WARNING

This receiver has been designed to meet or exceed applicable safety and x-ray radiation protection as specified by government agencies and independent testing laboratories.

To maintain original product safety design standards relative to x-ray radiation and shock and fire hazard, parts indicated with the symbol on the schematic must be replaced with identical

parts. Order parts from the manufacturer's parts center using the parts numbers shown in this service manual, or provide the chassis number and the part reference number.

For optimum performance and reliability, all other parts should be replaced with components of identical specification.

HORIZONTAL OSCILLATOR DISABLE CIRCUIT

This chassis employs a special circuit to protect against excessive high voltage and beam current. If, for any reason, the high voltage and beam current exceed a predetermined level this

protective circuit activates and detunes the horizontal oscillator that limits the high voltage. The over-voltage protection circuit is not adjustable. However, if components indicated by the

symbol on the schematic in either the horizontal sweep system or the over-voltage protection circuit itself are changed, the operation of the circuit should be checked using the following

procedure:

Equipment needed to check the disabled circuit:

High voltage meter (0 ~ 50kV)

Variac or isolation transformer

D.C. current meter

Digital voltmeter

PREPARATION

Connect receiver to A.C. 120 Volts. Do not turn ON.

Connect HIGH VOLTAGE meter to 2nd anode (H.V. button).

NOTE

Use cold ground for negative lead.

Connect the ammeter serial from the flyback anode lead to the picture tube anode socket.

PROCEDURE

Apply a monoscope or white pattern.

Confirm that beam current is 2.0 mA.

Adjust VR524 so that high voltage is 28.5 ± 0.3kV.

Adjust VR538 so that digital meter reads 2.3 ± 0.05V

Confirm that high voltage protector (SOS) operates at 33kV or less by adjusting VR524.

Turn VR524 counter clockwise, turn tv on and apply a monoscope or white pattern.

Adjust VR524 so that high voltage meter reads 28.5 ± 0.3kV

Once the adjustment is completed, apply a bond on VR524 and VR538. Confirm B+ 142V ± 6.0V with 120V A.C. applied.

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11/3/2008