Used ICs: TEA1533AT (SMPS controller), TF6NK90Z (SMPS switching FET), PT11400 (Remote control IC), TDA9570 (Syscon Chroma Jungle), TDA1517 (Audio output IC), LA78040 (Vertical scan output IC), BU1508DX (Horizontal scan output transistor)
This circuit have been used with many brand CTVs. The main fault found with this circuit is the breakage of the Horizontal scan output transistor (BU15508DX). If this transistor is found leak (Collector to Emitter), be sure to measure the frequency at pin number (30 – HOUT) of IC TDA9570H. In most cases this frequency will vary very high than normal. If you found this frequency to be very high (it can be measured without inserting a new horizontal transistor in place), make sure it to be under limited frequency; usually between (15500 to 17800 Hz), before replacing the horizontal output transistor, otherwise the transistor will get damaged again, as soon as you switch ON the set, not giving any chance to you checkout the fault.
More to say, if the deflection yoke (Horizontal scan side winding) have an internal short in between its windings, this transistor will overheat in no time, and will fail. So after replacing this transistor, check the heat of the transistor, periodically at about 2 minute’s interval. It might get warm, but not too hot. Feel this heat at its heat-sink.
Click on the schematic to magnify
Another possibility is with DC output voltage from the SMPS converter. If this voltage go beyond normal [High], the transistor will get damaged. If you found this voltage to be abnormal, check and clear all the faults with the SMPS circuit first.
The components used in the SMPS of this circuit are cheap and easily available at the local electronic spare part market. When work with it, just replace all the main components; (SMPS switching transistor, the opto-coupler and the control IC (TEA1533), all at the same time.