Won A War With One Induction Cooker Make Prestige Model PIC 19.0
This Induction Cooker (hereinafter referred to as ‘IC’ for the sake of brevity) belonged to the hospital, where I worked band had visited me in November, 2023 with a capacitor dry solder problem. Kindly see the following link to know the background:
https://jestineyong.com/arcing-capacitor-found-in-prestige-induction-cooker-model-pic-19-0/
I am taking the liberty of skipping basic images, as these are already covered in the above article. This was brought back to me after a few days with the complaint that it just gets on and no buttons on the panel works. I observed that the membrane on a couple of buttons on the panel were torn and saw traces of liquid. I opened the IC and did the normal tests that we do to check whether the voltages were ok, any resistors have changed the values, any capacitor leaky, any dry solder, any symptoms of heat up, any damages due to liquid seeping inside the panel etc. I saw that the press to on buttons on the control panel had marks of liquid leaks under it and traces of fungi formation.
As Kerala Climate is prone to fungus attacks, this was not a surprise. I replaced all the push to on buttons on the panel board, cleaned everything thoroughly. Also replaced two high value resistors, though these were tested ok and checked the dropped down voltages that goes as a feedback to the µController. Then replaced the three SMD transistors 8050 & 8550, which also was a routine replacements we all do while repairing the ICs.
In spite of all these routine checks and remedies meted out, the IC refused to respond and posed a challenge. Since all the LEDs and the display were found lit when I switched on the IC and the fan rotated slightly, I did not suspect a software issue. But none of the buttons including the on/off switch functioned. The 18V was ok and the 5V was also ok.
After getting fed up with my trouble shootings, I sought help from my techie friends, and after explaining what all I did, they were also aghast! But their advice had limitations as the device was not in front of them. So, I kept the IC aside and handled other pending jobs. In between, I used to pick up this IC for checking with new ideas and hoping that some angel would have heard my silent prayers and helped me by resolving the issues and it might suddenly work! (LOL) In this process, weeks and months passed. The department which was using the IC, went for a new one as per my advice after waiting for a week. But my ego was hurt badly and this unresolved case was gnawing my heart every now and then. Then one day, after successful repair of two ICs, I took this up. This time, I used my oscilloscope to check the SCL & CLK pulses that go to the µController. Then I saw that these wave forms were jittery. There was no change in the wave forms when any buttons were pressed. Then I suspected that there was indeed something wrong in the panel itself. After rubbing and cleaning the Panel Controller Integrated Circuit, (I am not using ‘IC’ here to avoid confusion! Ha, Ha!), I got somewhat cognizable image to read its number. But any attempt to fetch a datasheet of this Chinese component was futile.
Then, I remembered that I used to change all the fixed value caps of panels, which I did not do in this case, as these were SMD caps and were found ok when checked with my SMD tester. So, I removed these caps one by one and replaced it.
There were four such caps; 1nFx2, 10nFx1 and 100nFx1. Then just for the sake of double check, I tested the 100uF/16V electrolytic capacitor on this board and look at what I found:
The value was 94.95uF with ESR of 8.3 Ohms. Just compare it with a new cap that I tested, shown above; the value is 99.07uF and ESR is just 0.16 Ohms. Then when I checked my previous records, I did not seem to have replaced this cap and how I missed it still eludes me! Anyhow, I crushed the capacitor as a remorseful action and replaced it. Then the IC seems to have got life and started responding to all functions on the board. In order to conduct such tests, I had removed the IGBT from the board in the first stage itself and connected two wires to the Induction Coil keeping it slightly away. Kept one stainless steel plate on top of the induction coil over a cardboard to prevent direct contact.
There was no danger of heating, as IGBT was not fixed on the board. Just have a look at this make shift arrangement:
But the wave forms were still not steady and it had a little bit of noise. So I traced the two tracks that go to the µController (Incidentally, no datasheet of this could be fetched! The number seems to be S009L NCLS4-1) and found two SMD caps and when I removed the caps, the values were shown as 0.1nF.
I replaced these two upon which, the wave forms were better and all buttons on the panel worked very well. I was glad to see the following result:
In the second picture, you can see how the wave forms were steady and how it responded to a button when pressed, triggering the input signal fed to the main Integrated Circuit on the mother board. Then I resoldered the IGBT, connected the coils and temperature sensor, and tested the IC keeping a vessel with water on the top and the control panel by its side. It worked very well with hot water boiling within minutes.
Having satisfied that the IC has got back to perfect working condition, I moved it to my kitchen and used it a few times before fixing the back screws and giving delivery to the Hospital.
Mission accomplished with greatest satisfaction ever that of a war won, getting added to the bag!
This article was prepared for you by Parasuraman Subramanian from India. He is 74 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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You may check on his previous article on Strange Case Of Elec. Cap Defect In SONY LCD TV RC Unit
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Albert van Bemmelen
September 7, 2024 at 7:04 pm
There is just too much war going on these days to connect such evil doing with successfully fixing electronics, even although it was just a matter of speaking. These are dangerous times in which we now can be killed by AI driven drones and robots.
But I am happy that you in the end won your fight with a strange almost unrepairable IC!
Parasuraman S
September 7, 2024 at 9:10 pm
Many thanks for your encouraging expert comments! Yes, AI is a threat we need to now face! But experts like you would master it soon, for sure!
John
September 7, 2024 at 10:28 pm
PERSISTANCE! Just 10yrs older agrees with your will to Learn beyond your years.
Use Real Intellegence (RI) and Time and the River (TR). So RI + TR gain success when 1st level strategies fail. I own your willingness to Get Er Done (GED) as offten and let my Lord instruct me over night and Ah Ah in the morning. CHEERS!
Parasuraman S
September 8, 2024 at 3:00 pm
Vow! That was a poetrical comments with deeper meanings! Vow again! Many thanks for making this forum more and more interesting to participate!
Mark J
September 8, 2024 at 2:26 am
Parasuraman S Well done on the repair.
Parasuraman S
September 10, 2024 at 8:17 pm
Many thanks, dear Mark!
Imoudu.O
September 8, 2024 at 5:18 am
It's obvious we all need almighty God in all our daily endeavours,as you expect an angel to induce you on what to do next after applying human effect. In the end you succeed and the bag can not but to open wide and receive a genus repaired work.More grease to your....!
Parasuraman S
September 8, 2024 at 3:01 pm
Many thanks for your wonderful encouraging comments, dear Imoudu! May God bless you!
GIFT ELIJAH
September 8, 2024 at 10:17 am
Congratulations Sir, you truly won a war I like your determination and persistence a never giving up spirit. Even when you were expecting some angels to assist you with ideas, you kept on keeping on and you finally won the battle.
As at the time you kept a cardboard paper on top the coil and placed a stainless plate on the paper if it was working, will the paper not get burnt and caused damage on the coil or the PCB?
Parasuraman S
September 8, 2024 at 3:04 pm
Kindly read this comment : 'There was no danger of heating, as IGBT was not fixed on the board. Just have a look at this make shift arrangement.'
Many thanks for your encouraging comments, dear!
Yogesh Panchal
September 8, 2024 at 6:04 pm
GOOD JOB! Sir,
Now you will start all future diagnostics with capacitors which you missed here to obtain as a culprit here....ha ha ha
Parasuraman S
September 9, 2024 at 5:56 pm
Ha! Ha! Sure I will do, my dear Yogesh! Thanks for your comments!
Imoudu.O
September 9, 2024 at 1:45 am
Suppose igbt was fixed and cardboard is placed on coil with stainless steel pot place on cardboard, will still be electromagnetic energy produce between coil and pot?
Parasuraman S
September 9, 2024 at 6:03 pm
Logically, it should, as it passess through the glass top. But I never have ventured to try it! Many thanks for your comments, dear Imoudu!
Waleed Rishmawi
September 10, 2024 at 2:08 am
Not an easy repair but you won this time because you did not give up. Your repair challenge was inspirational to me and I thank you for sharing. Have a blessed day.
Parasuraman S
September 10, 2024 at 8:18 pm
Many thanks for your encouraging comments, dear friend!