High Voltage Or Lightning Caused PWM IC Burst In PRESTIGE Induction Cooker
MAKE AND MODEL NO: Prestige Induction Cooker Model No. PIC 1.0V
COMPLAINT REPORTED: Dead
PRELIMINARY OBSERVATION AND WORK:
Opened the Induction Cooker (hereinafter called ‘IC’ in this article), found a lot of cockroach eggs, excretions and a couple of living ones too! It was serving as a haven for these disgusting insects! I saw also cobwebs inside! I dismantled the boards and coil. After giving a thorough clean of inside, during which I got the top portion of the PWM IC Viper 12A, which had burst, I cleaned the PCBs too very well. I did all that outside my house, as I did not want any of these pests to start its haven here. (There is not even a single cockroach in my house, and we two ensure that none gets in! During the summer days, I have seen these trying to enter flying or running on the floor! But none survived to start migration! We use anti-cockroach sprays like ‘HIT’ periodically!)
TROUBLESHOOTING AND RECTIFICATION DONE:
After bringing the boards to my workshop table, I used the ring tester to check everything else is ok in the SMPS section. As all the LEDS lit brightly indicating that there are no shorts in the primary or secondary, I replaced the burst IC. Looked for any defective components in the primary or secondary section. Found the 10 Ohm Fusable Resistor open in the AC input section. But Fuse was intact. Replaced the Resistor. As I saw the small induction coil (through which the DC comes to IGBT section) had collected fungus and looked to be in a bad condition, replaced it. It was a good thing I did, as one leg of it came off itself! Normally, technicians do not check this, even though this plays an important role! Applied power and noticed that the Panel got on and it responded to commands. So, after doing a thorough dry solder patch-up, and replacing all the electrolytic capacitors and the front panel switches (a few of which were showing high resistance), I rechecked the high watt resistors, diodes and transistors on the board. All looked to be good. So, placed the board back in its case, placed the coil on top of it, took the panel to the side for operating it, kept the ceramic top on the coil, kept water in a stainless steel vessel and applied power. All looked well for a few minutes. But suddenly the IC broke down tripping the MCB of that line in my house. I knew that IGBT had failed, which meant that more preventive work had to be carried out. Once again dismantled the IC. Removed the failed IGBT, H15R1203. As a routine and regular method of rectification in almost all ICs, replaced all the high watt resistors, IGBT base driving transistors SS8050 and SS8550.
Since exact values of resistors were not available, I had to connect a few in series to get the correct value. For example, for 240K, I used two 120K in series; for 200K, two 100K in series etc. As I wanted to know the root cause of the failure, I checked the transistors using Analogue Multimeter, keeping it in X1 Ohm range, as advised by Jestine Yong in his repair books. As the readings between Base-Emitter and Base-Collector were not even, I knew that the transistor had developed leak. I compared it with the new ones to make sure and it showed correct readings on both sides. So, that was the culprit. Then once again checked the other components on the board for any leak and conformation to the values marked, for which sometimes I had to lift one leg (not mine, the component’s (LOL)). As I could not find anything wrong, I replaced the IGBT with FGA25N120, which is a better and sturdy one from experience, reassembled and tried heating like before. This time it worked very well. After trying it a few times, fixed the screws of the bottom cover and left it in my kitchen for couple of days. As it was found to be working without any problems, informed the customer to come and collect. Mission accomplished generating another ‘satisfaction’ ball, which was happy to roll itself into its collection bag!
TIME FOR PICTURES TO REVEAL THE WORK DONE:
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.
Please give a support by clicking on the social buttons below. Your feedback on the post is welcome. Please leave it in the comments.
P.S-If you enjoyed reading this, click here to subscribe to my blog (free subscription). That way, you’ll never miss a post. You can also forward this website link to your friends and colleagues-thanks!
You may check on his previous repair article below: