A guy next door who is in the business of selling computers and computer screens brought me an LCD computer screen. The problem was ticking noise in the speakers and there was no picture.
I connected it to my laptop at the shop and there was ticking noise coming out of the speakers and the LCD panel was dark.
I have seen this kind of problem before and it was an easy fix. The moment I took the cover off, I could see a bad bulged capacitor in the secondary area of the power supply. It was a 1000uf/25 volt. Usually when there is a bad capacitor in that area, I check the others to make sure all of these capacitors are in good working conditions. All of them checked ok.
I replaced the bad capacitor and tuned the machine on. I still could hear the ticking noise coming out of the speakers. I was one step ahead when I replaced that bad capacitors but seems like there are more bad components in that area that needed my attention. I turned the machine on again and started doing voltage testing. There was a steady 300 volts at the main capacitor but when I tested the voltages at the secondary diodes, there were voltages there but not steady which gave me the indication that something is wrong in the power supply.
I asked myself, why the bulged capacitors why there is only one that has this problem, so I traced it back from that capacitor and near by it there was an SMD component that was kind of melted component. Near that SMD component was writings near it. This component was supposed to be a Zenner diode. Under a large magnification, I could read on that component 7.5 A. after a long search on the net, I came to a conclusion that this is a zenner diode 7.5 volts. I replaced it with another zenner diode but not SMD component. I soldered it in its place and turned the machine on. The ticking noise was gone and I could see the NO SIGNAL sign coming on the LCD panel.
I connected it to my laptop and I could see a picture coming on and the sound was great. I let it run for about an hour with the cover off to make sure that nothing is over heated especially that zenner diode that I soldered on that board. It was working fine. The voltages were steady and that zenner diode was ok.
I called the guy, actually yelled his name just outside my workshop door and he came running. He was happy that the machine is working fine. I was happy to see it come to life. It was great and the pay was even better.

About

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.

3 comments on “An LCD computer monitor repair. Model Harma 983A

  1. Muhammad BASHIR says:

    A very useful information, But it will very helpful for beginners if you include the Pictures also.

  2. S THULASIRAMAN says:

    Ya I too fix this same problem in this same method for finding….

    Your Very Good Diagnose Knowledge.

  3. reza says:

    hi Waleed Rishmawi
    very good article
    plz attach pic of pcb monitor and characterize the diode ziner
    tank u

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