Panasonic SP-2725F Schematic

ORDER NO. MTNC020307A1 B5

Service Manual

Color Television

Simplified Manual

(NA7DM)

Quasar

Models

SP-2725F SC363 SP-2725UF SC363

This simplified service manualis issued to add listed models to the simplified service manual, order No. MTNC020101A1 (CT-27G7F); Unique schematics, settings and a complete parts list are included in this simplified service manual. Please file and use this simplified service manual together with the simplified service manual, order No. MTNC020101A1 (CT-27G7F) and main service manual, order No. MTNC010306C1 (CT-27G6E).

“WARNING! ThisServiceManual is designedfor experienced repairtechniciansonly and isnot designedfor use bythe generalpublic. It does not contain warnings or cautions to advise non-technical individuals of potential dangers in attempting to service a product. Products poweredby electricity should be serviced or repaired only by experienced professionaltechnicians. Any attempt to service or repair the product or products dealt with in this Service Manual by anyone else could result in serious injury or death.”

Chassis

The service technician is requiredtoreadand follow the “Safety Precautions”and“Important Safety Notice” in this Manual.

Important Safety Notice

Special components are used in this television set which are important for safety. These parts are identified on the schematic diagram by the symbol and printed in BOLD TYPE on the replacement part list. It is essential that these critical parts are replaced with the manufacturer’s specified replacement part to prevent X-ray radiation,

shock, fire or other hazards. Do not modify the original design without the manufacturer’s permission.

Safety Precautions

General Guidelines

An Isolation Transformer should always be used during the servicing of a receiver whose chassis is not isolated from 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,suchas fishpaper, isolation resistors and capacitors, and shields after servicing the receiver. Use only manufacturer’s recommended rating for fuses, circuits breakers, etc. High potentials are present when this receiver is operating. Operation of the receiver without the rear cover introduces danger for 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 nick 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 provide shielding for the tube viewing area against x-ray radiation as well as implosion. The magnetic shield limits the x-ray radiation around the bell of the picture tube in addition to the restricting magnetic effects. When using a picture tube test jig for service, ensure that the jig is capable of handling 50kV 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 operate. Do not use a

line isolation transformer when testing.

Leakage Current Cold Check

Unplug the AC cord and connect a jumper between the two plug prongs. Measure the resistance between the jumpered AC plug and expose metallic parts such as screwheads,

antenna terminals, control shafts, etc. If the exposed metallic part has a return path to the chassis, the reading should be between 240kΩ and 5.2MΩ. If the exposed metallic part does not have a return path to the chassis, the reading should be infinite.

Leakage Current Hot Check (Fig. 1)

Plug the AC cord directly into the AC outlet. Do not use an isolation transformer during the check. Connect a 1.5kΩ 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.

Figure 1. Hot Check Circuit

X-ray Radiation

WARNING: The potential source of x-ray radiation in the

receiver is in the High Voltage section and the picture tube. Refer to “X-ray Protection Circuit Check & Adjustments” on page 6 to confirm HHS voltage.

High Voltage (CRT Anode)

Set the brightness, pic ture, sharpness and color controls to minimum (to obtain dark image). Measure the High Volt age. The high voltage should be

29.25kV ± 1.25kV . If the upper limit is out of tolerance, immediate service and correction is required.

Note: It is important to use an accurate, calibrated

high voltage meter.

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About lead free solder (PbF)

component

Note: Lead is listed as (Pb) in the periodic table of elements. In the information below, Pb will refer to Lead solder, and PbF will refer to Lead Free Solder. The Lead Free Solder used in our manufacturing process and discussed below is (Sn+Ag+Cu). That is Tin (Sn), Silver (Ag) and (Cu) although other types are available.

This model uses Pb Free solder in it’s manufacture due to environmental conservation issues. For service and repair work, we’d suggest the use of Pb free solder as well, although Pb solder may be used.

PCBs manufactured using lead free solder will have the PbF within a leaf Symbol stamped on the back of PCB.

Caution

• Pb free solder has a higher melting point than standard solder. Typically the melting point is 50 ~ 70 °F(30~40°C) higher. Please use a high temperature soldering iron and set it to 700 ± 20 °F(370± 10 °C).

• Pb free solder will tend to splash when heated too high (about 1 100 °For600°C). If you must use Pb solder, please completely remove all of the Pb free solder on the pins or solder area before applying Pb solder. If this is not practical, be sure to heat the Pb free solder until it melts, before applying Pb solder.

• After applying PbF solder to double layered boards, please check the component side for excess solder which may flow onto the opposite side. (see figure below)

component

remove all of the

excess solder

slice view

solder

Suggested Pb free solder

There are several kinds of Pb free solder available for purchase. This product uses Sn+Ag+Cu (tin, silver, copper) solder. However, Sn+Cu (tin, copper), Sn+Zn+Bi (tin, zinc, bismuth) solder canalsobeused.

0.3mm X 100g

0.6mm X 100g 1.0mm X 100g

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ImportantSafetyNotice...................2

SafetyPrecautions .................2

Aboutleadfreesolder(pbf)...........3

ServiceNotes...........................5

X-Ray Protection Circuit Check

&Adjustments..................6

Receiverfeaturetable...............7

PartsList...............................8

A-Boardschematic......................14

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Service Notes

Note: Some components may be affixed with glue. Be careful not to break or damage 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 1.6kΩ resistor, 0 = 0Ω (jumper). 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.

Chip Components

How to Replace Flat-IC

- Required Tools -

• Soldering iron • De-solder braids

• Needle nose pliers • Magnifier

• Wire cutters (sharp & small)

1. Cut the pins of a defective IC with wire cutters. Remove IC from board. If IC is glued to the board, heat the IC and release the IC. See Note above.

Flat IC

2. Using soldering iron and needle nose pliers remove the IC pins from the board.

Soldering Iron

3. Using de-soldering braid and soldering iron remove solder from affected are on board (pads).

De-soldering Braid

Soldering Iron

4. 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). Determine the positions of the soldering pads and pins by correctly aligning the polarity symbol. Solder pin #1 first, align the IC.

Polarity symbol

Solder the pin opposite to pin #1. This will assist positioning the IC.

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

2nd solder

1st solder

Solder

6. 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.

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Soldering Iron

IMPORTANT: To protect against possible damage to the solid state devices due to arcing 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 ( ) or

( ) 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.

X-ray Protection Circuit Check & Adjustments

This test must be performed as final check before the receiver is returned to the customer. If voltages are out of tolerance, immediate service and correction is required to insure safe operation and to prevent the possibility of premature component failure.

Equipment:

1. Isolation transformer.

2. High voltage meter.

3. Short jumper.

4. Jumper diode (same as D823, PN S3L60P154004). diode should be rated a minimum of 150V.

Procedure:

1. Connect the receiver to an isolation transformer. turn receiver ON.

2. Apply a monoscope pattern.

3. In service mode (see service mode section in this manual) select register C0B.

4. Measure TP5 (located near the tuner). Compare the measured value to the left column of the table below. Set C0B with value from the right column corresponding to the measured level at TP5. Example, if the measured level at TP5 is 1.03V, set C0B to 03.

TP5 MEASUREMENT SET C0B TO (HEX)

0 ~ 0.93V 00

0.93 ~ 0.97V 01

0.97 ~ 1.01V 02

1.01 ~ 1.05V 03

1.05 ~ 1.09V 04

1.09 ~ 1.13V 05

1.13 ~ 1.17V 06

1.17 ~ 1.21V 07

5. Exit service mode and shut the TV OFF.

6. Connect the short jumper between TPD16 and TPD17.

7. Connect the jumper diode between TPD14 and TPD15 (cathode connected to TPD14, anode connected to TPD15).

8. Apply 75VAC to the input of the isolation transformer.

9. Turn receiver ON.

10. Set PICTURE and BRIGHTNESS to minimum.

11. Slowly increase the voltage at the input of the isolation transformer and confirm HHS voltage measure 35.0KV when the receiver starts to go out of sync.

12. Turn receiver OFF and remove jumper & diode.

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+ 14 hidden pages