philips tv problem

[takos]

hello everybody , i need help for a philips tv set 29pt5306/01.When I turn it on the picture comes slow, smaller with alot off defacement and with a white vertical line at the middle only for some secs.Then the flyback tranzistor goes very hot and the stby led gets low brightness.I have replace already the tranzistor because it was shorted. What can cause that?

[bbp1]

Check LOPT/ section/ yoke etc/ components etc - there are no magic wands- just careful analysis/ remedy.

[torbjorn]

Another possibility is that the transistor gets too weak base drive for some reason, so that it does not saturate properly. It might be due to low supply voltage to the driver stage, bad supply decoupling capacitors etc. If there is no driver transformer but capacitor coupling to the output transistor base, then this capacitor should also be suspected.
Check the waveforms at the output transistor base and (only if you have a high voltage probe rated for at least 1500 V) at the collector to see if those can give any clue.

[takos]

Thanks for your replies.There is driver transformer with coupling capasitor that I will check.The yoke seems ok...

[xora]

Good morning.
I had the same problem and changed the capacitor 2455 (47mf / 35V).

[abr]

I have a philips tv , the Horizonyal transistor ( BU508F) was shorted and i just changed it but it was shorted even it didn't stay for seconds & i just changed another original transistor but again it's shorting every new changed transistor, so what couold be the problem plz

[jts1957]

Check Horizontal Drive circuit.