Horizontal Deflection coil resistance

[rng]

i am having a problem with lg 14 inch crt monitor (LG 1467 Chasis- CA-32)in which horizontal output transistor blows off after replacement, but it is happening after say 10 to 25 mins normal working, i had changed EHT transformer also. pl help me to fix this problem..

Then tell me how check horizontal deflection coil resistance, my present situation this monitor is showing approx 0 ohms. vertical deflection coil it is showing 8 ohms..

please send me the detaild service manula for the above monitor

my email id is rng_hemrl4@yhaoo.com

thanks in advance

[torbjorn]

It is very common that horizontal deflection coils have so low resistance that they cannot be measured with an ordinary multimeter. Typical values are between 0,4 and 0,8 ohms. If you have instruments to measure inductance of the coil, it can typically be 180 to 500 uH. If a mid tap of the coil is accessible, then you should have equal inductance in both halves.

But if the coils were at problem, then the monitor would not work properly the first minutes after replacing the transistor.

I think you should first check whether the transistor is very hot immediately after having failed. In this case, the problem is probably due to bad drive to the transistor's base. Check the driver stage for bad solder joints or bad electrolytic capacitors, and check the waveform at the base of the transistor with a scope.

If the transistor does not get hot when it fails, then the problem is probably due to overvoltage. For instance, due to a flyback capacitor that has gone open circuit or due to a problem in the circuitry to switch in different flyback capacitors depending on actual horizontal frequency that can be found in some monitors.

Also, make sure that you use the monitor at a horizontal frequency which it is officially said to support. Some monitors might sync and produce a useful picture even outside of their intended frequency range.