Audio Systems: SONY TV reear Projection convergence, power supply voltage, frequent failure

Question
Hi Mr. Cleggsan,

I have a SONY rear proj TV model KP61V45.
Question: How can I fix this problem?

At times:
MODE I
a) The top of screen the display is curved downwards, and
b) The  bottom of screen it is curved upwards, and
c) The convergence is off; the red can’t be adjusted.

MODE II
At other times:
All screen is perfect and
then I can adjust the convergence perfectly (from the menu)

I t switches by itself from Mode I to Mode II and vice versa.

I am electronics experienced with practical experience in repair work.

Thank in advance for your advice.
Spencer


Answer
Can you tell what causes it to go from mode 1 to mode 2?  Is it walking across the floor?  Does it switch when you bang the set with your hand or fist?

I think the problem is clearly convergence circuit trouble. But it must be determined what is causing it to fail. For example, if some mechanical disturbance will trigger it to go out of convergence it is likely to be a cold solder joint or loose connection in that circuit area.

But, if the set is doing it on its own it is either a bad power supply (voltage regulator part, maybe) or the STK chips in the convergence area.

It is common - or rather a frequent failure - for the two STKs to go bad.  They are not too difficult to replace and usually cost around $30 each.  If you have a shop do it the cost will run around $400.

But, before replacing the STKs you really should determine if the other two possibilities are the cause.

Cleggsan

PS: If you have a voltmeter, monitor the voltage feeding the convergence circuitry and see if it drops down when the picture goes out of convergence.

PPS:  YOu can get the STK here at a very cheap price, but I don't know of their quality.  If you order the part from Sony Parts it will cost many times more.

http://www.electronix.com/catalog/product_info.php/cPath/6_308/products_id/9360