Ramtons Microwave Model RM266 Come In Dead Now Repaired
I received this microwave from a member where I worship, I have repaired several of her items and hence referred me to a friend whose microwave had a problem.
As you know, satisfied customers always come back and refer back more customers, that is how I survive during these Covid times my friend. Since the lady was not the owner she did not have any history about the microwave and therefore I took it off to my workshop.
First I plugged to the power outlet and noticed the microwave has no life in it. Checked the main power fuse and found it okay, I tested the voltage at the input power connector and got zero volts. I decided to check the power cable plug fuse and also found it okay, with that I concluded the cable must be broken inside which is very rare. I substituted another cable and this time I was able to get the 240 Vac.
I did some scanning and noted the bulb has blown, I did a substitute quickly from another microwave. I applied the power and still nothing happened, I opened the door and I noted the bulb now lights, fan is rotating and the turntable motor is rotating but no display. I closed the door and the three components stopped working.
In real live case scenario those components are supported to work when the door is closed but in this case they are behaving opposite. This means I need to do further troubleshooting to find out why the erratic behavior. The next destination is the control board.
Control board receives its power from this small transformer. First was to confirm if this small transformer is getting voltage(240Vac) and yes I got the voltage at the input pins.
Next was to check if there is output from this transformer but instead removing the board I decided to test using fly-back tester. Don’t worry this is a do it yourself meter I did over 8 years ago and still serves me well.
As you can see only one led is on and this means even before removing it out of the circuit, I can tell its faulty.
I removed the board and soldered it out of the circuit and replaced with another one I had salvaged from the junk.
Before replacing I had to confirm it is working, make it a practice to test components from the junk otherwise could be the reason it is there is because of that component.
After passing the test I proceeded to replace and also confirmed in circuit otherwise sometime components failed on the secondary of the transformer can give same results of a faulty transformer.
In circuit test also looks good! This means no component sorted on the secondary side of the transformer.
Then I decided to assemble the control board back and apply the power and see the progress.
Display is now working, waiting for next instruction. Learn more on microwave oven repair here.
Thank you friends
Humphrey Kimathi is from Nairobi Kenya and the author of:
4) Basic Electronics course.
He is also a blogger at Electronicsrepairmadeasy.com
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