Used IC TDA1105PS [Syscon-VIF-Oscillator-Chroma jungle.] (Chinese KIT)
LOT number: BSC 25-N0625
The set do not starts up. The power LED blinks continuously. A clear evidence; that the fault is with main board circuit itself. The SMPS section circuit is OK. Otherwise, the power LED won’t light up.
On checking further, a multi-meter test revealed that the Collector to Emitter junction of the Horizontal Output Transistor [HOT] (D1651C] is Leakey.
Shows about 3 Ohms DC resistances across these two terminals. Un-soldered it out from the circuit and measured again. The leak confirmed.
The +B voltage was OK. At bout 111.5VDC; without load [w/o Horizontal Output Transistor].
Replaced the Horizontal Output Transistor with its exact substitution (C5296); as D1651C was not available. Switched ON the set. OK.
The raster (Blue screen) appeared. But; it blinks occasionally; along-with a sparking noise.
On further checking; I found that the EHT cap (Boot) has burned, and causes sparking.
Replaced this Silicon Rubber Boot with a new one.
Switched ON the set. No other problem detected.
Tuned in an on-air program. Perfect picture.
Attention: Before you unclip the EHT boot, make sure that the storage voltage at the final Anode has been discharged fully; otherwise severe shock hazard be the result.
Be sure that there is no loose soldering to the free-wheeling capacitor; connected between Collector terminals of the Horizontal Output Transistor to Ground. [0.01MFD – 1.6KV]. Either this capacitor is open; or any of its solder terminals [2 of it] has loose solder, no doubt, the Horizontal Output Transistor will get damaged; at the instant we switch the set ON.
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