Problem: Dead: no display, and no stand by led.

I always start with this technique on every equipment. I look for bad soldering joints or burnt component using my magnifier lens but there was no sign of any faults in this monitor.
I headed directly to the horizontal output transistor (HOT) and found out that only 11 volts reaching that transistor and that is not enough to make the monitor work. This situation gave me the indication that something is either in the HOT itself or there is something wrong in the power supply section.

I took the HOT out from the PC board and checked and found it to be good. Due to the good voltage, now I concentrate on the power supply section. There was only 11 volts measured at the diode in the secondary output which give me more assurance that the power supply is not functioning the way it should be.

I scanned the power supply again, but this time taking every component out and check one by one. I found two Zener diodes next to each other that did not check ok. I replaced two of them and to my surprise the monitor was alive again but with a deflection problem. Well, I am one step ahead but still there is more work to be done on this monitor.
The vertical IC TDA8172 was getting some voltages but all minus readings. That told me that the IC is not getting the supply voltage and that what is causing the IC to malfunction. I found another part a resistor (R263) which supposes to be 4.9 ohm and it gave me a high ohm reading which indicates a bad fuse resistor.

Here, I did a bad mistake which is replacing the resistor without checking the vertical IC and when I turned on the monitor, the resistor started to burn which gave me the impression that the vertical TDA8172 is shorted which explain the current drawn by it and burnt my new resistor. I directly replaced the vertical IC and the boost capacitor next to it and the monitor is alive again. I tested the monitor for about two hours by hooking it up to my laptop and it worked nicely.


10 years of practical electronics. owner and operator. I service the Bethlehem area in Palestine. I repair Xbox 360 and all play stations and modify their power supplies. also repair lcd and Plasma tv sets, and lcd computer monitors. I have a degree from Bob Jones University in general business and one year degree in Industrial electronics. a intensive course in Media. I also work as a camera and audio man as a free lancer. Also great experience in video editing and installing surround systems for home and movie theaters.

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