2 Service notes
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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 1.6kΩ 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
Use solder wick to remove solder from component end caps or terminal.
Without pulling up, carefully twist the component with tweezers to break the adhesive.
Do not reuse removed leadless or chip components since they are subject to stress fracture during removal.
Chip component installation
Put a small amount of solder on the board soldering pads.
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)
Remove the solder from all of the pins of a Flat IC by using a desolder braid
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.
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.
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 partscenter 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 oscillatorthat 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, theoperation 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
1k ohm VR
D.C. ammeter
PREPARATION
Connect receiver to A.C. 120 Volts. Do not turn ON.
Connect HIGH VOLTAGE meter to 2nd anode (H.V. button).
Use cold ground for negative lead.
Connect the ammeter serial from the flyback anode lead to the picture tube anode socket.
Prepare HHS jig to be connected between TPD50 and TPD51 on P-Board as shown above.
PROCEDURE
Open connector A17.
Turn power ON and apply a white pattern.
Set current within 50-100μA by changing the picture and bright controls.
Turn power OFF.
Connect HHS jig between TPD50 and TPD51 on P-Board as shown above (VR should be turn fully clockwise).
Turn power on.
Using the variable resistor slowly increase the current until the horizontal sync frequency abruptly increases indicating that the horizontal frequency is just beginning to pull out of sync. Maintain the current within 50-100μA bychanging the picture and bright controls
Observe the high voltage meter. High voltage should read less than 38.4kV.
Turn power OFF, remove HHS jig, HV meter, ammeter and connect A17 connector.
Turn power ON. Reset PICTURE and BRIGHTNESS controls. Confirm B+ 144V±1.5V with 120V AC applied.
If high voltage is not within the specified limit the cause must be determined before the receiver is returned to the owner.