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About X-RAY protection pin

By on September 6, 2012

xray protection circuit tv

If you are repairing CRT TV or Monitor, you will notice that there is a pin called as x-ray protect in one of the pins in the horizontal/vertical oscillator ic or even in Jungle chip (please see pin 2). The function is to detect any abnormal voltage feedback by the flyback so that if the feedback voltage is too high, it will shutdown the internal generator and no horizontal output pulse will be produced. If no output pulse the HOT will not switch and if the HOT does not switch the flyback will not be energized thus no high voltage  produce.

If you want to isolate the shutdown problem you cannot just remove the pin of the x-ray protect and expect it not to shutdown. If you referring to older model then YES, by removing the x-ray protect pin the equipment will not shutdown. But then again it can be dangerous to you or to the user if you just return the set back to the customer. Why dangerous to you, because when you disable the x-ray protect pin and continue to troubleshoot you could be exposed to x-radiation.

If the TV or monitor have shutdown symptom, the first thing to check is if the B+supply voltage is too high or not. If it is too high then definitely it will shutdown and you need to check on the optoisolator circuit. The next thing to check is the safety capacitor. If the capacitor value is out, high voltage can be increased thus shutting down the equipment (thanks to the x-ray protect circuit). A bad or leaky flyback transformer also could cause shutdown problem. If you are repairing CRT Monitor and the internal capacitor in the flyback transformer have an open circuit, it could also cause shutdown problem.

Conclusion-if you want to defeat the x-ray protection pin for temporarily troubleshooting it is ok but not too long and please do not entirely defeat the pin (without finding the real cause) and send the equipment back to customer. This will truly harm the user.




  1. Vijay

    September 6, 2012 at 6:14 am

    I have a 12v power adaptor, can i use it to charge 12v 7.2A SLA Battery?. thanks.

    • Jestine Yong

      September 6, 2012 at 9:06 pm

      Hi Vijay,

      Different battery type need different type of charger. For example if you are using a normal power adapter on the lithium battery it will explode. The usual charger voltage for sla battery is about 14 volt and 12 volt is not good enough to charge it. I suggest that you get back the sla battery charger to do the work.



  2. bogie

    September 6, 2012 at 11:57 am

    Thank you very much for this blog Sir its another useful topic...1 request Sir, can you discuss about HEATER in CTR Tv,how it works and how to troubleshoot? thanks...

  3. vijay

    September 7, 2012 at 1:12 am


  4. amir mukhtar

    September 19, 2012 at 8:42 am

    Highly informative knowledge about   XRAY  Function in monitors.
    thanks you

    • Jestine Yong

      September 19, 2012 at 9:13 am

      Hi Amir,

      Welcome back!


  5. Stanley

    February 27, 2017 at 2:50 pm

    Thanks for very useful x ray circuit and trouble shooting


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