Control Panels Of Microwave Ovens With Same Symptoms But Different Reasons
Two control panels of Microwave Ovens were brought by a technician for possible restoration. Both the panels had the same problem. The Digital display would stay frozen and not respond to any control switches. But sometimes it would work after switching on for a considerable period and sometimes it would not. Well, these types of intermittent problems would need combing the entire power supply as well as the uController IC boards and you know then why were these brought to me!
Case (1) Panasonic Micro Wave Oven – NNCD671M:
My first step in such cases is to ensure that it is getting a stable power supply. When I checked the output of 5V, it was showing around 6.4V and the 12V was showing around 19V. So, I did a dry solder patch up of the board and also replaced all the electrolytic capacitors as the values were not proper. But even then the problem remained same. I tried giving an external 5V, cutting the track of its own PS board.
I used a borrowed PS board from my expert friend and tried, but even then the result was same. I looked for any leaky switches and replaced a few in the start area. I combed the uController IC area and did a thorough retouch of all the solders and even heated the IC to clear off any fungus formations. But nothing made it work. Unfortunately the number of the IC was unreadable and I could not get a datasheet or replacement because of this.
Then I sent the board to my expert friend and he too tried all possible ways and concluded that the uController was defective, as I had even tried by replacing the crystal oscillator. He too combed the entire boards to look for any defective components and could not find any. (Forgot to mention that all tests were done with the door switch shorted, without which nothing would work) So, we had to give it up.
Case (2) Samsung Micro Wave Oven – MW83H:
Since symptom was same, I did all the checking work on the PS board and control section (This was a combo-single board) like in the above case. The customer also brought a similar PS board, which had its burnt components in the primary section for any possible salvage.
After doing all the tests, the conclusion was that the control panel touch switches were leaking and shorting inside. As I had no time to do a replacement of the membrane switches with press to on switches, I sent it to my expert friend who did the job neatly.
Since the board was delivered directly to the technician, I could not switch it on and take a snap. Though I had requested the technician customer to send me a snap, there was a last minute hiccup, as his customer bought a new oven and did not want it back, because of the delay in service. The board got stuck with him, but he paid our charges without any hesitation. Well, such reactions from customers are all expected and what we normally do is to take an advance when we deal with such potentially troublesome customers.
Can the satisfactions get collected in the bag? Only if the readers let it in! Its just waiting for your nod! (LOL)
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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Albert van Bemmelen
February 18, 2024 at 10:55 pm
So far as I know you could not have fixed the MW oven even if you were able to get a new processor. Because that one was likely pre-programmed with matching firmware by the manufacturer. And a new blanc replacement processor would not solve it, which unfortunally is the way in how these days modern equipment is designed.
Parasuraman S
February 19, 2024 at 8:40 pm
Yes, dear, you are absolutely right! Many thanks for your expert comments!
Yogesh Panchal
February 19, 2024 at 12:58 am
Good Attempt! Sir
is there any RESET option available in this Microwave oven ??have you tried..
Now a days there is restriction in repair because of unavailability of spare in the market.
Parasuraman S
February 19, 2024 at 8:41 pm
No reset option. Many thanks for your comments and suggestions!
Imoudu.O
February 19, 2024 at 5:04 am
This time around the two devices have refused to yield to your expertised fingers.Well the other one that was fixed can gradually be pushed into your ever size- increasing bag.
How i wish to know how to replace membrane switches with press on switches.Thanks for sharing sir
Parasuraman S
February 19, 2024 at 8:43 pm
You just practise the button replacement in some not working boards that can be fetched from scrap yard. Then you will be able to do it on a real working Oven. Many thanks, dear!
R Lamparter
February 19, 2024 at 11:42 pm
On board #1 I'd take partial satisfaction from diagnosing the problem.
On board #2 the customer's need wasn't met, but did he give you a time frame when he left it for repair? If not, you never had the opportunity to let him know you might not be able to meet his time expectations. Partial satisfaction on #2 also because the board was repaired. If he left the old microwave with your tech friend it can be sold. Then there's the factor of the man's wife who probably wanted it to be fixed 2 minutes after it was found to be broken. She's the one most inconvenienced by the microwave's failure. The customer may have had to buy a new microwave in the interest of maintaining domestic tranquility.
Parasuraman S
February 20, 2024 at 12:26 pm
Oh! Ha! Ha! Let that wife not read this! She might come hunting down, if we can believe what you assumed about her! (LOL) Thanks for permission of satisfactions to take entry! There was no time frame given and the technician did not push me, which most of my customers alson won't dare to try with me! I mercilessly return all those devices, if the customers are found sitting on my head! I prefer to handle the job easily and relaxedly. No hurryburry at all! I have around 39 sets pending with me right now, some of which are many months old! Thanks for your comments and humour, which I thoroughly enoyed!
Waleed Rishmawi
February 20, 2024 at 5:12 pm
interesting repair attempts. all we can do is try our best and if it did not work, then we learn from it and move on. I deal with microwave oven repairs but never encourtered this model before. if you can send me the ic part number that is needed I will be more than happy to check and If i have it would send it to you. have a blessed day
Parasuraman S
February 20, 2024 at 9:07 pm
Many thanks dear friend! As mentioned by Albert van Bemmelen, there is no point in getting the IC without its loaded program. Moreover, the number was not readable too!