An Electronic Scale That Does Not Power Up Repaired
A customer working in a company that sells medical supplies brought this dead scale to my shop for repair. It is a very sensitive scale because it is used for measure very tiny and light things.
This is the model number and when the customer brought it for repair, it was already open.
The customer explained that the technician at the company tried to repair it but without any success.
When I took the top cover off I saw what the other technician has done. All these capacitors have been changed but that did not bring this device back to life.
As I powered up the device I could read the entire voltages fine and there was nothing wrong with that except it was not turning on. What could be the problem?
The only thing that came to mind is the power switch gone bad. So I started figuring out the connections of the on/off switch.
If you look at the photo you can see the configuration of that. All these lines tested fine except the on/off switch. It was faulty.
I was thinking about peeling off the buttons pad but there was a risk of damaging the other buttons in the process so instead I decided to add an external pulsed on/off switch.
The pulsed on/off switch was added and tested and seems like I forgot again to take a photo of the repair results. Any way, it was working fine.
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-multi-meter-with-the-issue-of-bad-display-repaired/
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Albert van Bemmelen
October 2, 2020 at 8:44 pm
Good job in fixing this important medical scale! Although the photo explaining the wiring to the bad on/off switch only raised questions on what you exactly tried to explain. Never heard about 'tare wire' before either?
Waleed Rishmawi
October 3, 2020 at 1:45 am
Albert: Tare wire is the connection that leads to the tare button.
Parasuraman S
October 2, 2020 at 10:17 pm
That was an innovative idea to save the device! Well done!
Waleed Rishmawi
October 5, 2020 at 2:26 pm
Parasuraman: thanks man. have a blessed day
babums
October 3, 2020 at 12:10 am
Very very good job,nice idea that your introduced pulsed on/off switch. Thanks for sharing.
Waleed Rishmawi
October 5, 2020 at 2:27 pm
Babums: thanks man. you are most welcome
Waleed Rishmawi
October 3, 2020 at 1:18 am
Albert: I do not understand what are you trying to say
Albert van Bemmelen
October 3, 2020 at 4:05 pm
Hi Waleed. I was only wondering what was with all those arrows in the photo of the on/off switch. Because it didn't explain how you connected the push button to it. But that 'Tare wire' was only about the meaning of measuring Tare weight is clear now because obviously there are no tare wires.
Waleed Rishmawi
October 5, 2020 at 2:28 pm
Albert: it was meant as a way how I traced the on/of button wires. other buttons were ok but th off/on was the bad one. thanks. have a good day
Yogesh Panchal
October 6, 2020 at 12:10 am
Waleed,
Some basic stage-wise troubleshooting is save our lots of time.
well done!
Waleed Rishmawi
October 7, 2020 at 1:17 pm
Yogesh: indeed. have a blessed day.