In my tv fuse is blowing off immediately
If fuse blows off immediately, i means that there is a short circuit occured in your telivision. This can mainly due to some diodes or regulators inside your tv. An overvoltage, spikes, ie [sudden high rise and go low], in the supply votage in your home, could damage power supply regulator components inside your tv.
All Sony Tvs has high accuracy power regulating systems inside. It is an onboard assembly, usually take 1/4th of the area of the TV. In older Sony TVs, this section was built in with use of transistors of different types. But your tv is not so old, so its power supply system is built with an STR, an Ic meant only for power regulations. Normally it willb numbered STR S6707, STR S6703 etc; according th the working voltage of the main board, and screen size of the TV.
This STR may get shorted due to power fluctuations, or any other reasons. A I mentioned above this is an Ic look like small squuare biscut of about an inch in square, and will be black in colour.
The rectified main power supply is given to it via an SMPS transformer [Swiched Mode Transformer], and the Ic will swictch it on and off at the rate of sbout 25KHz or more, and this transformeres secondary voltage is used to power up the other part of the ciiruit board.
If the fuse is blowing as soon as the set is switched on, this Ic will be faulty [Shorted inside]. If you put an another fuse, it also will blow up due to short. It is not good to play with power supply system by doing this as it may harm to other components also.
You have done it I thinks. Here in India, we gets 220VAC as home power supply. Sony TVs used here have a fuse rateing of 250V 3.5Amps. If your household supply system voltage is also this you must put only this rated fuse. If it is 110 or 120VAC, the fuse rating may differ; and will go upto 6 to7 Amps. More than this rated fuse should not be used.
You just do one thing. Just open the back cover of the TV, locate the power regulator section, and chech whether any main rectifier diodes for leak. There may four of them. In some sony Tvs, rectifier stalks are used. Check it for leak. If thery are all good, measure the resistance across the main filter capacitor with a multimeter set in Ohms range. If the STR said above is short, the meter will give full scale deflection. Unsoder the STR and pick it out after loosing its fixing screws to the heat sink. Again check the resistance accross the main filter capacitor. It must sho a low deflection or no deflection at all. Never replace the STR with a new one as there may be some other faulty components in that section. Usually when STR fails, there are some Zener diodes, Wire wound resistor etc will also gets shrted. If you replce the STR before checking them for fault, the STR you puts in will get shorted as you swich on the set. It will take just 1/100 part of a second.
So check all the components related with power regulator system, and then only repace the regulator. Caution: Keep chlidren away from you while you open the tv. Never touch any part of the circuit board while power supply is there. Plug out from the wall socket each time you touch the printed circuit board. As your Tv screen size is 32", an approximate of 25KVDC [15,000VDC], will be present at the first anode of the picture tube while it is working. It is too dagerous to contact.
If you haven't through knoledge, skill and patience, never try to repair it. If you knows to follow its schematic digram, buy one book and follow the circuit.
Keep an adult beside you as you try to repair your set, as a precaution.
If you have any doubt, report to Fixya, they will give me alert. Ok
Oct 20, 2010 |
Sony FD Trinitron WEGA KV-32FS120 32" TV