A photographer in a nearby store brought this LCD computer screen to my shop. The problem was a blinking stand by light when hitting the power button. After hitting the power button for 4-5 times, the screen comes on but for a while then it shuts down.
The moment I heard that from the client, I know it was a capacitor problem. The guy told me that he sent it to another repair guy but he could not figure out the problem. So I told him, I will do my best in solving this problem in this LCD monitor.
I took the cover off, and started checking for bad capacitors in the primary and the secondary sections of the power supply and all checked out ok. I moved to the high tension area of the board and I found two capacitors. They were 1000uf/25 volts. I checked them with my ESR meter and both of them gave me a high reading indicating a problem there.
I replaced both of them and rested the LCD computer monitor and it worked fine. I connected the monitor to my laptop and let it run for more than two hours and it did not shut down.
I called the customer who was really shocked that is actually worked. I asked him a question to where he sent the LCD computer monitor to be fixed. It turned out that this guy is a computer guy and has no experience in electronics repair. I gave the LCD monitor to the owner and he paid well for the repair and told me how happy he was to deal with such a guy like me. He said that he has a lot of computer monitors and a lot of electronic equipment that need to be fixed. I was so happy that he liked my worked and that more repair work coming to my shop soon.
This also gave me an idea about the computer guy who could not fix the LCD monitor. I called this guy and then I went to meet him in his shop. We talked about working together; He installs computers and I can fix things needed for his customers. I was so happy to make this deal and that my business is moving forward.
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.
The problem was it does not weld; At least that what the customer told me. Later on I realized, it was a different problem and was very easy to fix.
I took the cover off and turned it on and nothing happens, I was suppose to hear the cooling fan spinning but I did not, instead, I could smell something burning and the smoke was coming out of the cooling fan. I turned it off and looked closer at the fan. I tried to spin it by hand but it did not spin. It was a bad burnt fan.
A bad not spinning fan does not mean the welder is not working. The machine is working fine but the fan is very important in that machine. If the fan was not working and the machine is working, eventually, after a while the machine will go into shut down causing over heating caused by a fan not spinning and cooling off the machine.
It was a 220 volts fan. The motor was completely burnt and the plastic around the motor was melting and it smelled bad. The only problem I was facing in this machine is the ordering of a new fan. It takes about a week or so to get it and the customer was in a hurry to get it fixed. I called so many stores but without any luck. I have to place an order and wait for it.
I remember a while ago, someone brought me a DC welder to be fixed but it was too expensive and the customer did not come by the shop to pick it up. I went to the storage room and found the machine. There were two working fans in that machine. I called the customer and told him if he is interested to sell the DC welder for a cheap price and he said he not need it and offered me to take it for free. That was nice music to my ears; I took the old machine to the shop, took one of the working fans out and installed it in the machine I was working on and the fan worked very nicely.
I took the machine to my brother’s shop next door, connected all the wires needed for the welding process and turned it on. The fan started to spin and my brother tried the machine. It was working fine.
Called the customer to come and pick up his machine. He was so happy that the machine was working fine and was fixed in a very short time. He was happy, I was happy. Case closed.
A friend of mine brought this TV to my shop not for repair but to give it to me to use for parts or sell it. He just bought an LCD 32” TV and wanted me to have his old CRT TV. It was a big 29” TV, Korean made and it was really heavy.
I plugged it in and I could hear only audio coming out of the speakers and only a horizontal line across the screen. This is a deflection problem and it cost only about 10 dollars to fix. So I decided to fix that and see if I can sell it cheap.
I opened the cover of the TV and started measuring voltages on the pins of the IC. I could see 40 volts on pin 9. This testing is very important. Before changing the vertical deflection IC, you need to make sure there are voltages reaching the IC. Usually these 25-40 volts come from the fly back transformer. One of the pins of the fly back transformer will give out usually 25-40 volts then it goes through a diode to change it from AC to DC, then it goes through a resister fuse, usually 1-3 ohms 1-3 watts. Sometimes, the fuse resister will be open causing this problem to appear on CRT TV.
The vertical deflection IC TDA3654 is very easy to find on board. It has a heat sink and usually it is very close to the Yoke sockets. I could not find TDA3654 in the electronic shops around me but instead, I put a TDA3653.
I replaced the bad IC with the new one but did not turn on the TV yet. It is very important to check the capacitors around this IC. Sometimes bad capacitors cause the vertical IC to go bad again. Check the capacitors before turning the TV on. I found two bad capacitors that had a high ESR reading. It was a 1000uf/25 volts and 100uf/25 volts.
I turned the TV on after connection a picture/Audio source. The sound was great and the picture was great. After five minutes, I could see horizontal lines on the top of the screen and the picture started shaking. Usually this is a capacitors problem and based on that, I started checking the capacitors in the power section area and the vertical deflection area as well. Found some bad capacitors there but it did not solve the problem. I touched the IC with my finger and realized that the IC was getting hot causing this problem to show on the screen. I used the hair dryer to make the IC hot so it will speed up the repair time. The problem got worse as I was applying hot air to the IC. I applied cold air to the IC and the problem disappeared. There was something wrong with the IC.
I started studying the specification of the IC I replaced. The bad IC TDA3654 is the original one and it can handle temperature 90-110 C but the TDA3654 can handle only 90 C degrees. It does make sense, once it got hotter; the IC was acting up showing this problem on the screen.
I looked for the original TDA3654 and found it, used one actually. I replaced it and I tested the TV for more than three hours and it worked nicely. It was a long repair time but was not wasted in vain. I have learned a few things, but most important, I know now that TDA3653 is not a replacement for TDA3654.
A dead CRT was brought to my shop by a friend of mine. He said that this TV suddenly stopped working. I could see a stand by light but there is no high tension sound, no audio and no picture.
I took the cover off and scanned the area for bad capacitors and found no bad ones. I plugged it in and started testing voltages in the power section area. There was 300 volts reaching the main capacitor and there was 24, 110, 10 volts coming out on the secondary diodes in the secondary power section.