Horizontal Output Transistor Failed In Samsung CRT TV With China Kit
MAKE AND MODEL NO: Samsung CRT TV fit with China kit
COMPLAINT REPORTED: Dead
HISTORY: This Samsung CRT TV Model No. CB20D8V2X/XTL had visited my workshop on 22nd October, 2015 after getting affected by lightning. As the main board was damaged beyond economical repair, I replaced the board with a China Kit. As a routine, whenever I fit a China Kit, (as a last resort only), I do retouching of all the solder joints, change its tank capacitor and rectifier diodes and even the SMPS Transistor in certain models of China Kit. Otherwise the kit will fail within a short time. This is the experience many of my Techie friends shared with me. This could be the reason why the set worked very well until it was brought to me on 27th April, 2020; i.e., after about 4 years and six months!
TROUBLESHOOTING AND RECTIFICATION DONE: Checked the fuse and found it was blown. Most probably some component is short in the primary itself. Checked the SMPS Transistor D1710 and found it to be dead short. Replaced it. Replaced the driver transistor and opto-coupler too. Found one 1.5K Resistor burnt in the ABL line of FBT (Value of this was informed by my Techie friends). Replaced that too. Replaced one Blue 1KV cap in the SMPS as part of the routine. Removed the B+ rail to FBT, connected a Bulb Load and found that the 110V was restored in the TV. I had also connected an LED to between the Base and Emitter of the Horizontal Output Transistor to check its oscillation. It was Ok. As the component fatigue or failure in the ABL section is a clear indication of wearing out FBT, replaced that too. Then reconnected the B+ rail to FBT, loaded the PCB to the CRT and switched on. The set was working perfectly well. After ensuring that it was working for hours without any problem, put back the cover and called the customer to pick it up. Mission accomplished and satisfaction got added to its collection.
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This article was prepared for you by Parasuraman Subramanian from India. He is 70 years old and has more than 30 years’ experience in handling antique equipment like Valve Radio, Amps, Reel Tape Recorders and currently studying latest tech-classes conducted by Kerala State Electronics Technicians’ Association. He has done graduation in BBA degree, private diploma in Radio Engineering and retired as MD of a USA company. Presently working as Consultant to Hospital and other institutions.
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