IN MY MONITOR HORIZONTAL OUTPUT TRANSISTOR(C5855) FOUND SHORT. I REPLACED IT BUT AFTER FEW MINUITS IT BECAME SHORT.AFTER CHECKING I FOUND A DIOD(MUR460L)SHORT.I WANT TO KNOW THE FUNTION OF THE DIOD AND THE EQUIVALENT DIOD FOR REPLACE (BECAUSE MUR460L IS NOT AVAILABLE IN OUR LOCAL MARKET).
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Re: LG 500G MONITOR
As your h/output got defective due to short circuit.proceed as follows.
isolate h/output section fom power supply& check power supply output is ok as you know high output may give such problem.
when it becomes ok, check hor.section
2 cap & diode connected in eht winding.
3 ptint short near eht.
4 at last eht tranf.
5 if it is ok re connect h/output supply.
put on set.
AFTER CHECKING I FOUND A DIOD(MUR460L)SHORT.I WANT TO KNOW THE FUNTION OF THE DIOD AND THE EQUIVALENT DIOD FOR REPLACE (BECAUSE MUR460L IS NOT AVAILABLE IN OUR LOCAL MARKET).
1 Function of diode is to convert AC TO DC
2 you can use BF159 or BF157 as equivalent.
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You have to check the pin control transistor in the horizontal section. It will be fitted on the same heatsik on which the horizontal output transistor is fitted.It will be a small transistor as compaired to the horizontal driver. Also you have to check the three mosfets in this section used to control the width.
your irf 630 is not original purchase it from proper LG authorised service centre it is costly but never become faulty again duplicate mosfet overheats if your green led is on then measure voltage at E.H.T.connect meter at output transister if E.H.T. is producing then meter should show 1 digit if not then 50v will show take care that signal cable should be disconnected if E.H.T. is not producing then check +vcc at horizontal ic it should be 12v. if 12v is not present then check regulator ic 7812 insmps
Check components related with pots thats adding command ic to pots.If they are ok then change command ic with new one.Before this you can check horizantal hold transistor that is placed on hitsink of eht.small in size and check two small transistor placed near it on pcb.Hope this solution works .If not then i am here
The horizontal output transitor is always connected to the primary winding of the flyback transformer (via collector) and also to the horizontal deflection coil via an electrolytic capacitor.
The most likely suspect for damaging the transistor is the fylback transformer. In some countries there are electronic stores that test flyback transformer by winding a few turns on the ferrite core and applying a test voltage. This test will only test the secondary.
The primary winding is difficult to test for turn to turn short because the resistance is quite low and you do not know the 'good' resistance.