A Dead Microscope Was Brought Back To Life
A lap technician from out of town brought his for repair. I have repaired a lot of stuff for the company he was working with. This time, it was his personal microscope and it was completely dead.
It was already opened and the light bulb inside was missing.
I asked him to bring the light bulb so I can test out when the repair is done.
As I took the cover off, I was able to spot right away the black burn on board. It was located in the output circuit of the board.
As I got closer, I found two bad components; a capacitor was completely blown to pieces and a diode. From the marking on the board I knew the missing part was a capacitor but I did not know the value of it.
I replaced the shorted burned diode and headed directly to find the value of shattered to pieces capacitor. I could not find any schematic for this device and I was stuck for a while.
An idea came to mind to see what kind of capacitor found on that board and then come up with a value or at least close to that value.
I noticed that most capacitors found on that board were 222M and right away I replaced it with a capacitor that has the same value.
As you can see in the photo an exact replacement of the capacitor found on that board.
This is the replacement capacitor but before I power up the device, I checked all the surrounding components for short but could not find any. I applied the light bulb trick to the main fuse which by the way was intact; the result was great.
I had one problem though; the customer did not bring the light bulb to test it out. He lived far away and was not easy for him to come and pick it up.
I unplugged the main cord that goes to the light bulb of the microscope and powered up the device. I did voltage measurement there and I got 12 DC volts there. Sorry I could not take a photo of it.
I could put a 12 volts light bulb there but sad to say I did not have any in my shop with those ratings.
I had to send this device in the mail and after few days he informed me that it was working like a charm.
Mission Accomplished.
This article was prepared for you by Waleed Rishmawi, one of our ‘Master Authors’ and currently working in the Bethlehem area of Palestine repairing electrical and electronic equipment.
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Note: You can check his previous repair articles in the link below:
https://jestineyong.com/a-shorted-electronic-welding-machine-repaired-model-caddy/
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Henrique J. G. Ulbrich
August 3, 2019 at 11:36 pm
Very good, Waleed. I`ve never repaired microscopes, so it´s a new knowledge to me. You teach me, and I am very grateful. Just a doubt: What is a lap technician?
Waleed Rishmawi
August 5, 2019 at 3:39 pm
Henrique: thanks. it was my first microscope repair too. I am glad you liked it. Lap technician is a person who works in lap testing things..like blood type...etc. have a blessed day
Parasuraman Subramanian
August 3, 2019 at 11:44 pm
Reading the caption, I rightly guessed it could ONLY be you! Well done! A master's solution!
Waleed Rishmawi
August 5, 2019 at 3:40 pm
Parasuraman: thanks man. have a blessed day
Albert van Bemmelen
August 4, 2019 at 1:10 am
I guess it is better to use just a good value for the unknown replacement capacitor than no capacitor at all. And it is at least the same type of component design-wise as the bad one was.
Waleed Rishmawi
August 5, 2019 at 3:42 pm
Albert: yes it is and according to the customer the microscope is still working fine which indicates that I used the right capacitor..have a blessed day
Yogesh Panchal
August 14, 2019 at 8:57 pm
Well Done! Waleed
Zaid farjan
August 26, 2019 at 7:19 pm
Am puzzled I got a speaker system the tweeter 150w 8ohm blown the crossover used a lamp as current limiter which blewout n here I don't get that part I would like pls if u could tell me if I can substitute it with a normal fuse and pls tell me the rating