Etech Hot and Cold Water Dispenser Repaired
The complaint of this Etech hot and cold water dispenser was it has power and the “hot” side can work but the “cold” side was not giving out cold water. As usual in order to check what is wrong with the dispenser one has to open up the cover and do a visual inspection first.
Visual inspection check is to locate any loose cable connection, burnt component, dry solder, decayed glue, and etc. From the visual inspection check, I found the right side of the circuit board seems to have problem. Look at the photos below:
Guess the water had entered into the circuit board causing short circuit and hence the NTC thermister (negative coefficient thermistor) and the diodes burnt. Surprisingly the main fuse did not blow.
I started to check all the corresponding components in this area and found six components were bad. There were four shorted diodes, cracked NTC and a shorted Dual Schottky Barrier Rectifier. If you do not know how to test component, I suggest that you get Jestine Yong’s Testing Components Ebook HERE.
I bought the new components and fixed into the circuit board.
Like any other power supply test, just before you power up the board, you need to connect a light bulb in series with the fuse (fuse had to be removed) and I saw a very dimmed light and then the light fade off. This was a good sign that I can power up the circuit board now without any hesitation. After putting back the fuse and powered On the water dispenser, the “cold” side worked normally again.
This article was prepared for you by Suranga Bandara who owns an Electronics shop in Anuradapura, Sri Lanka.
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Note: You may check out his previous repair article in the below link:
https://www.jestineyong.com/polytron-led-tv-repaired/
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Petrica
October 14, 2015 at 12:50 pm
Good job! Thank for presentation.Your presentation is professional all time.
Albert van Bemmelen
October 14, 2015 at 1:11 pm
Thank you Suranga. Well done job. On pcb boards that are likely to come into contact with moisture or water you better use varnish paint to isolate the components. Also on boards that use components like Opamps that are going to be placed in the outside (like Cooling controller boards in Farmhouse pigstables) it is wise to protect your components. At least that is what my boss did with every controller board that left his Manufacturing place. Even the boards in the well known Senseo Coffee maker I believe are varnished. Also to protect the user from touching the Power line Voltage I guess. And it also protects the copper solder side of the board from getting oxidated. (the greenish oxide of copper). But of course making it harder to desolder components in future too.
Mark
October 16, 2015 at 10:43 am
Hey Albert,
Varnishing a board in wet areas sounds like a wise idea, but......do you know an easy way to remove the varnish so that you can desolder components? I have worked on varnished boards and they are a pain to remove the solder from.
I am open to suggestions 🙂
Albert van Bemmelen
October 16, 2015 at 11:25 pm
Sorry Mark. My chemical knowledge of this stuff is limited. I only know about Bases and Acids and the easy to remember things. Mol or Mole quantities and such theoretical knowledge is something that lost my interest. I only know about how to easily clean Cooling Paste from CPU's and Coolers on the Xbox or on PC Coolers. I know the best way to clean them is by using Turpentine or also called White Spirit. Also known as paintremover. The best part of Varnish is always that is very good covering and sticking to the things that get sprayed. Because it doesn't need any workover and sticks very long easily. My Boss used Spraying Cans for Varnishing Opamp controlled Boards.
Andre Gopee
October 14, 2015 at 8:41 pm
Thanks for the article Suranga, Job well done.
randy
October 15, 2015 at 12:18 am
isn't that typical, you would think the fuse would blow instead of so many components, but its the components that burn leaving a lot of work and the fuse just sits there...
Albert van Bemmelen
October 20, 2015 at 2:52 am
Hi Randy, I guess the Fuse just re-Fused, Haha. (just as in defect SMPS Power supplies often is the case). Cheers.
Yogesh Panchal
October 15, 2015 at 2:53 pm
suranga, good job thanks for sharing.
Paris Azis
October 15, 2015 at 9:05 pm
Good job Suranga.
Ulises Aguilar Pazzani
October 16, 2015 at 9:36 am
Mr Suranga with Your experience a good job
Humberto
October 16, 2015 at 10:15 pm
Good job Suranga.
Am
September 15, 2017 at 10:34 pm
May i have the part number for the ntc? Mine is same model but completely burnt, thankyou