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  First 10 Faults By Observing Symptoms

Introduction to Fault Finding By Observing Symptoms

We have already studied about the kind of defects which may have happened in observing symptoms in the receiver: additional let us observe how a fault can be found out through observing symptoms in the receiver.

1. DEAD FAULT

If a TV receiver does not work properly, means no raster and sound, this type of fault in termed as Dead fault.

WHILE SERVICING A DEAD RECEIVER PRECAUTIONS TO BE TAKEN

A.  Very firstly isolate the power supply from other sections and test the power supply.

B.  Discharge the high voltage capacitors.

C.  Test for short circuit and then only replace the fuse and operate the receiver, if fuse is blown.

D.  The recently replaced fuse should be similar Ampere rating as that of the blown fuse.

E.  Test the components in horizontal output, driver and oscillator in this order If power supply is OK.

THE POSSIBLE CAUSES FOR DEAD FAULT

If there is no output from power supply...

A.  Defective power cord, on/off switch

B.  Defective diodes, AC fuse, main filter capacitor

C.  Defective regulator transistor, their biasing resistors and zener diode

D.  If regulator IC is EMPLOYED, CALCULATE the poi voltages. If it is not acquired properly, test the related components.

E.  Copper print cut, Dry Soldering;

 F.  At last replace the regulator I. C, if needed.

Note: We cannot finish whether I.C. is defective or not through using a milli meter. It can be corrected only through replacement.

If Power Supply output is low,

H.  Weak filter capacitors in 110V and. 12 V

I.  Not proper adjustment supply preset.

If power supply output is high,

J.  Not proper adjustment of B + supply preset

K. Defective resistors, regulator transistors, resistors, Capacitors and Zener diode

If power supply output voltage is ideal, connect it with the other stages and compute the power supply output voltages.

If the output voltages are not dropped and also the receiver is still dead,

L. Horizontal output transistor, biasing resistors, driver and oscillator stages and related components might find opened.

If the output voltages are dropped after connecting with the other stages,

M. Shorted horizontal output transistor, fly back capacitor, damper diode and partial shorted horizontal deflection coil, L.O.T. and TV 20.

(Note: TV 20, L.O.T. and deflection coil are mainly partially shorted. We cannot recognize it correctly through using a millimeter. We can troubleshoot through replacement only).

N. Defective horizontal driver transistor, biasing resistor, transformer and other capacitors.

 O. Defective oscillator transistor, capacitors, biasing resistors, H.Hold preset (or H.H Q1old coil)

(Note: If Horizontal oscillator does not generate 15,625Hz, the horizontal driver and output amplifiers also do not function. The result, the receiver would become dead)

P. IfIC is employed in oscillator stage, test the pin voltages.

Q. Dry soldering copper print cut

R. At last replace the horizontal oscillator IC, if needed.

2. SHRUNKEN PICTURE OR RASTER

If the width and height of the picture appear uncommonly low, it is termed as shrunken picture or stamp type raster. This sort of defect appears mainly in portable receivers.

It takes place because of low household AC supply or low output from the regulated power supply. First to all tests by employing a voltage stabilizer.

REASONS:

There are 3 reasons expressed as follow:

A.  Defective biasing resistors, regulator transistors, capacitors, and Zener diode.

B.  Not proper adjustment of B+ preset.

C. Copper print cut; Dry soldering;.

3. HUM BARS AND HUM IN SOUND

If pure d.c. is not acquired in the power supply, this fault takes place.

A. Defective filters capacitor, rectifier diodes, and power transformer

B. Copper print cut; Dry soldering;

4. WAVY AND ROLLING OF PICTURE

If pure dc is not obtained, this type of fault takes place.

A. Defective filters capacitor, rectifier diodes, and power transformer.

B. Copper print cut, dry soldering;

5. VERTICALLINE ONLY

This type defect may take place, if the components in the path of horizontal deflection coil are defective. Since, if the driver, horizontal output, and oscillator stages do not function, no raster can be seen.

A. Disconnected wires to the horizontal deflection coil.

B. Open capacitor that is in series with the horizontal deflection coil.

C. Copper print cut; Dry soldering;

D. Open horizontal deflection coil and horizontal linearity coil (extremely rare).

6. HORIZONTALLY NON LINEAR PICTURE (OR) HORIZONTAL NON LINEARITY

A. not proper adjustment of horizontal linearity coil

B. Partial short in horizontal deflection coil (extremely rare)

C. Defective L.O.T. (extremely rare)

7. HORIZONTAL FOLD OVER

A. Defective horizontal output transistor and L.O.T.

B. Using not proper value of capacitor in horizontal output stage

C. Defective horizontal deflection coil

8. HORIZONTAL KEYSTONE EFFECT

It is also termed as horizontal trapezoidal raster.

A. Partial short in horizontal deflection coil.

9. BLOOMING OF PICTURE

If the contrast and brightness controls of a TV receiver are get increased, the height and width of the picture be apt to get increase. If the controls are decreased, so like the height and width of the picture. This- influence is said to be Blooming of picture.

A.  Defective EHT rectifier TV 20

B.  Weak L.O.T.

C.  Weak picture tube (Very rare)

10. BREATHING EFFECT

If the width and height of the picture is get raised and reduced automatically, this influence is termed as 'Breathing effect'.

A.  Defective E.H.T. rectifier, L.O.T. and picture tube.

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