A dead Elbit CRT TV repair. Model EC70-602-CTI
Two of these TV sets came to my shop and both of them had the same problem. Both were dead. When plunging both of them in, I could hear a ticking noise coming from inside the TV. I had to open the back of one TV set to find out what was wrong with it. In this case since both has the same problem, if I am able to fix one of them, there should be no problem fixing the other one. So, let us get started.
When taking the cover off, I scanned with my naked eye for bad electronic component but I could not find anything. From experience, when I hear a ticking noise coming from inside the TV set and the stand by light is not on, one thing comes to mind; the problem is in the high tension area. My focus now is in that area, mainly, the Horizontal Output transistor (Hot).
This is a made in China CRT TV set and was brought to my shop with a vertical deflection problem. Usually a vertical problem is shown on TV screen with a black screen and a line across the screen.
Most of the time, you can turn the TV and you could see the vertical line across the screen but in my case here, the TV was dead. I could not turn it on. The customer told me that a line across the screen came on and then the TV went dead.
I could read the 300 volts on the main capacitor and 124 volts was reaching the horizontal transistor. There was no high tension present and the stand by light was on but the TV was dead. From experience, I have seen it happen so many times that when there is a dead short in the vertical IC itself, it could affect the whole TV and in this case the TV was dead. To confirm my analysis, I checked the 25 volts coming out of the secondary section of the power supply and they were missing. The vertical IC has a dead short in it that it was pulling the 25 voltages down to 1 volts only. How did I know which ACC leg to look for to read the voltages? The only way to know is by checking the specification of the vertical IC online and you will know which leg that is getting the power. In my case, the vertical IC LA78041, leg number two was the power feed to this vertical IC.
The moment I soldered out the vertical IC, power came back to the set and I could see the vertical line across the screen. And I could read the 25 volts on the printed circuit. It is always a good idea to check for bad capacitors around the vertical IC. In my case, I found 6 bad capacitors there. Three capacitors 220uf/35 volts and three capacitors 450uf/16 volts. I replaced all of them.
I replaced the vertical IC and the TV came alive and I could see a picture but there was something wrong with that picture. The blue color was missing in that picture. Usually, there are too things to look for in such a case.
1- The blue color filament in the CRT neck is not working right. Usually there are three light in the neck of the CRT tube. Sometimes you could see them there if you dim the light in the room.
2- The transistor for the blue color in the CRT board is bad.
To my luck, when tested the transistor, it was shorted out. It was BF422. The moment I replaced that transistor, the blue color was restored.
It was lots of work but at the end, I won the challenge and the joy to see that TV come to life was wonderful.
This microwave oven was brought to my shop for repair and the problem was, it does not heat up. While the customer awaits in my shop, I did a small test. I put some water inside the microwave oven and tried to see if it heats the water or not. When turning on the oven, I could hear a loud noise coming from inside the microwave oven and it did not heat up the water.
From experience, when the microwave oven does not heat up, there is three possibilities:
1- The 220 volts is not reaching the main power transformer
2- The magnetron is shorted out
3- The .70 amp/5000 volts fuse between the 220 volts power transformer and the main capacitor is open causing the magnetron not to work due to the absence of power there.
By testing, I could read 220 volts reaching the main power transformer. The magnetron is not shorted out; This testing is done by testing the ohm reading between the metal body of the magnetron and the two terminals of the magnetron. If you get any reading between the terminals and the magnetron metal body, it is shorted and needed to be replaced. Usually the two terminals are connected together from the inside. It you test these two terminals with a continuity test setting, you will hear a beep. That is very normal.
I checked the fuse that is connecting the transformer to the main capacitor and it was open. this is a common problem in microwaves oven to find an open fuse there. Many repair technicians replace the fuse with higher amp rating causing the magnetron to blown or shorted it on the long run. It is very important to replace it with the same fuse specification to avoid any kind of problem in the microwave oven.
I replaced the fuse and turned the machine on. It worked and the water I put in the microwave oven started to get hot. One more problem remained; that is the loud noise of the oven. It was not suppose to have this loud noise. Usually, this is a problem with the main capacitor in the microwave and I think that is the main reason why the fuse was blown in the first place.
It is a very easy process to replace the capacitors but it is very important to make sure that the old capacitor in the microwave oven is discharged before replacing it. Even if the capacitor is bad, just make sure, it was discharged before replacing it with a new one. Upon replacing the old capacitor with a new one, the noise was gone.
The microwave ovens are very easy to fix and it can generated good income if you know how to do it. Just be careful when dealing with capacitors and magnetrons. Enjoy your repair and be safe.
An old man brought this satellite receiver to be fixed. It was a dead receiver. Took the cover off and scanned the power board with my naked eye but could not see anything there.
I powered up the receiver and started to test the voltages in the secondary power supply. All the diodes in the secondary section were not getting any kind of voltages whatsoever. That is an indication of a bad primary power supply. I tested the voltages at the main capacitor and I could read the 300 volts there.