Service Notes - Panasonic CT-26WX15N Service Manual

Leakage current hot check
Plug the AC cord directly into the AC outlet. Do not use an isolation transformer during the check.
Connect a 1.5k 10 watt resistor in parallel with a 0.15µF capacitor between an exposed metallic part and ground. Use earth ground, for example a water pipe.
Using a DVM with a 1000 ohms/volt sensitivity or higher, measure the AC potential across the resistor.
Repeat the procedure and measure the voltage present with all other exposed metallic parts.
Verify that any potential does not exceed 0.75 volt RMS. A leakage current tester (such a Simpson model 229, Sencore model PR57 or equivalent) may be used in the above procedure,
in which case any current measure must not exceed 0.5 milliamp. If any measurement is out of the specified limits, there is a possibility of a shock hazard and the receiver must be
repaired and rechecked before it is returned to the customer.
Insulation test
Connect an insulation tester between an exposed metallic part and A.C. line. Apply 2500VAC/60Hz for 1 second. Confirm that the current measurement is lower than 4mA. Repeat test
with other metallic exposed parts.
X ray radiation
WARNING
The potential source of x ray radiation in the TV set is in the high voltage section and the picture tube.
NOTE
It is important to use an accurate, calibrated high voltage meter.
Set the brightness, picture, sharpness and color controls to minimum.
Measure the high voltage. With a 480i or 1080i signal the high voltage should be 28.5 ± 0.3kV. If the upper limit is out of tolerance, immediate service and correction is required to insure
safe operation and to prevent the possibility of premature component failure.
Horizontal oscillator disable circuit test
This test must be performed as a final check before the receiver is returned to the customer. See horizontal oscillator disable circuit procedure check in this manual.

2 Service notes

NOTE
These components are affixed with glue. Be careful not to break or damage any foil under the component or at the pins of the ICs when removing. Usually applying heat to the component
for a short time while twisting with tweezers will break the component loose.
Leadless chip component (surface mount)
Chip components must be replaced with identical chips due to critical foil track spacing. There are no holes in the board to mount standard transistors or diodes. Some chips capacitor or
resistor board solder pads may have holes through the board, however the hole diameter limits standard resistor replacement to 1/8 watt. Standard capacitor may also be limited for the
same reason. It is recommended that identical components be used.
Chip resistor have a three digit numerical resistance code, 1st and 2nd significant digits and a multiplier. Example: 162 = 1600 or 1.6k
Chip capacitors generally do not have the value indicated on the capacitor. The color of the component indicates the general range of the capacitance.
Chip transistors are identified by a two letter code. The first letter indicates the type and the second letter, the grade of transistor.
Chip diodes have a two letter identification code as per the code chart and are a dual diode pack with either common anode or common cathode. Check the parts list for correct diode
number.
Component removal
1. Use solder wick to remove solder from component end caps or terminal.
2. Without pulling up, carefully twist the component with tweezers to break the adhesive.
3. Do not reuse removed leadless or chip components since they are subject to stress fracture during removal.
Chip component installation
1. Put a small amount of solder on the board soldering pads.
2. Hold the chip component against the soldering pads with tweezers or with a miniature alligator clip and apply heat to the pad area with a 30 watt iron until solder flows. Do not apply
heat for more than 3 seconds.
How to replace flat ic (required tools)
1. Remove the solder from all of the pins of a Flat IC by using a desolder braid
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Hot check circuit
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resistor, 0 = 0 (jumper).
11/3/2008