Lightning Damages Micro Controller IC In Philips 14” CRT TV
Make and model number: Philips 14” CRT TV 14PT2004/94R
History: This TV belongs to one of my relatives. This was brought to me in June, 2015. As the board was badly affected due to lightning, I had replaced it with a China kit for their immediate use. I kept the original board to look into the possibility of replacing the uController IC and making it work later.
Troubleshooting and rectification done: As I do not have enough experience in removing such ICs using blower and once I had very bad experience in an attempt made, I used a different method to remove the IC. I used sharp knives specially bought for this purpose. I cut the pins one set at a time carefully and ensured that all the 80 pins were free. Then applying gentle pressure, removed the IC, but not without dislocating some of the tracks! Minutely checked all the power supply tracks and positive/negative rails. Located a defective 78L33 IC (3.3V supply) and replaced it. Also replaced the AC capacitor (470n) in the SMPS primary. Ensured that the power supply was ok, by connecting a 100W bulb to the B+ line by disconnecting the supply to the Horizontal Output Transistor (HOT). All secondary supplies of the SMPS and those which go to uController IC were all found to be ok. Then cleaned thoroughly the portion where the uController was fit and laid the dislocated tracks to its correct position by pressing down by the tip of a flat screw driver. Then carefully placed the IC ensuring that pin 1 is in its correct position on the board. Then soldered 4 pins all the four sides first using a 12V sharp tipped iron. Rechecked and ensured that the IC was in its proper position and all tracks were correctly under the pins. Then soldered the next pin on each side one by one, by shifting the sides so as to ensure that the already flimsy tracks are not getting overheated. Using flat tipped 25W iron, rubbed the pins down gently so that the solder flows deep enough to make a proper bonding. Cleaned the portion thoroughly using IPA and repeated this until it was very clean. Inserted a small wire inside the gap between the pins and board to remove any left over flux. Once again used IPA. Checked for proper bonding and any man-made shorts using a Bluetooth Microscope Camera.
Applied power, connecting a 100W bulb as a load to the B+ and checked whether the uController was working by operating the remote control. It was responding to commands confirming that it was working. So removed the Bulb and restored the B+ supply to the HOT. Connected the board to a 20” CRT Tube kept by me for checking board and found that the Horizontal oscillator was working and raster was coming on to the screen. Applied a video signal and found that it was working well. Adjusted the screen and focus voltages tweaking it to its peak performance. Connected a speaker and got audio too. So, carried out my evertime amusement of replacing all the electrolytic capacitors on the board and retouching each and every solder point. Recheked by connecting it to the CRT Tube and found it to be working well. Thus another laborious but rewarding job completed satisfactorily and added to its bag.
The board was kept aside for replacement in its original TV, if and when it is brought for any rectification in future.
Here are a few pictures with descriptions:
This article was prepared for you by Parasuraman Subramanian from India. He is 70 years old and has more than 30 years’ experience in handling antique equipment like Valve Radio, Amps, Reel Tape Recorders and currently studying latest tech-classes conducted by Kerala State Electronics Technicians’ Association. He has done graduation in BBA degree, private diploma in Radio Engineering and retired as MD of a USA company. Presently working as Consultant to Hospital and other institutions.
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