SONY TV

SONY - KV-HA21 SERIES TVS. [WEGA COLOUR TELEVISIONS]

‘X’ shaped picture.  The picture will look like and ‘X’ shape, all the corners will be correct, but right and left vertical boarders will seem to be shrinked inwards at the middle portion.

The fault is technically called “Pincushion distortion” 

The fault is related with its pincushion distortion correction circuit.  It is composed of two Integrated circuits {Ics} (IC851 – MC4558CD) & (NJM2903M), along with three other transistors as pincushion outputs [Q850-Q851 & Q802]. 

    The components in this section will heat up while the TV works. Among the three transistors mentioned above, Q802 is a MOSFET.  It is the Pincushion Output transistor.  This transistor will be screwed on to a metal heat sink to radiate heat from it while it works. If overheats, this transistor will get opened, making no pincushion output, and the cause for the fault. 

     Just check all the solder terminals of components in this section for any loose solder points.  A loose solder points may be very minute that we can’t see it without using a magnifying glass. So it is advised to resolder all the suspected solder terminals of components in this section, by applying a little more solder, without making any solder bridge short in between adjacent solder terminals.  This is the first thing to do before replacing any component from this section. Check Q851 {PNP} transistor for short.  In most cases, this will be the fault.  Check R868-10 Ohms, R869-1Ohms, Zener diode D805.  Replace these components, especially the Zener diode, even if it tests well with multimeter test.

Replace the electrolytic capacitor, C865-100MFD 16V.  Check R888-220K, R887-220K and R889-100k for open.

IC failure to this section is very rare.  Even though if R889 mentioned above has open, and R887&888 are not, IC 851-MC4558CD will get damaged