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pete_bmw
Posted: July 07, 2014 11:20 pm
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Hello,

Electronics isint my primary skill, and althought i can understand it to a certain point, id like some help with repairing this PCB.

Someone please guide me in the right direction to repair this PCB. Its for an ultrasonic cleaner I need to repair.
Thanks

https://drive.google.com/file/d/0B8H9xPL27I...dit?usp=sharing

This post has been edited by pete_bmw on July 08, 2014 09:41 pm
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Sch3mat1c
Posted: July 08, 2014 10:22 am
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Says I need permission. Why not throw it up on imgur or photobucket or whatever?

Tim


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pete_bmw
Posted: July 08, 2014 09:40 pm
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Hello Sch3maitic!

Thanks for anwering.

ive modified the permissions, please check it out and see if it works now.

https://drive.google.com/file/d/0B8H9xPL27I...dit?usp=sharing

Thanks!
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CWB
Posted: July 09, 2014 12:23 am
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"for an ultrasonic cleaner ..."
that would explain the apparent water damage .
a schematic would help ... going to need part values .

is this the only portion of the board that has been damaged ?
also , this may not be as easy of a fix as it would seem to be ... there can be electrical/electronic damage elsewhere that is not physically obvious .


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Sch3mat1c
Posted: July 09, 2014 12:39 am
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Doesn't look obviously bad in that section, just dirty. Anything obviously burnt? Smelly? Corroded?


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kellys_eye
Posted: July 09, 2014 12:45 am
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Ditto - it just looks like the crud that came off the last thing you washed in the ultrasonic cleaner.

Clean cloth should wipe it right off.


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pete_bmw
Posted: July 09, 2014 02:52 am
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Thanks for the reply guys.

The board power on, and every button works except the one where the burn appears. It's the ON button (not the power button).

CWB:
There's no burn smell, it just stopped working. Maybe it did get wet and caused damage to that one section of the board only. The board is small, no other visual damage seems visible.

As for schematic or parts values I dont have, this is a cleaner from Harbor Freight - a hardware store that sells alot of chinese made hardware.

Let me know what you think.
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jlsgp
Posted: July 09, 2014 05:04 am
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A board may appear dry but moisture may remain inside switches and under IC parts, or between exposed pads.

Remove the ON switch from board and check its open resistance to see if any fluid is bridging the contacts points. Then check for high resistance with switch button depressed to see if contacts have oxidised.

Replace switch in either case.


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Bruce
Posted: July 21, 2014 04:48 am
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Hello pete

There are two possibilities for your reference:
1)There are apparent impurities in the resistor R38 area. if these impurities are electrically conductive, it will cause the change of the resistance, even shorted.

2)The second possibility, there are impurities into the button, lead to poor contact .
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This post has been edited by MacFromOK on July 21, 2014 04:56 am
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kl27x
Posted: July 21, 2014 08:58 pm
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QUOTE
A board may appear dry but moisture may remain inside switches and under IC parts, or between exposed pads.

Remove the ON switch from board and check its open resistance to see if any fluid is bridging the contacts points. Then check for high resistance with switch button depressed to see if contacts have oxidised.


This is a good place to start. Even better, check continuity of the switch while it's still ON the board. If it checks out good, the problem may lie elsewhere.

If you're really really lucky, it's just a broken switch. If you're really lucky, it's just a corroded or charred pcb that can be cleaned up. Any conductive crud or carbon/charring should be removed from the pcb, most effectively done with a fiberglass brush and alcohol, IME.

If you're not lucky, the problem is something less fixable and more about finding and replacing bad components.

One theory: water + electrolytes got around the switch and shorted the pullup directly to power. When you pressed the switch, a lot of current went through the switch. This current either broke the switch and/or caused heat that made electrolytes/carbon deposit around the switch, shorting the traces and/or pullup.
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pcblucking
Posted: December 24, 2014 07:32 pm
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try to replace a new switch, it may work. Or it maybe defeated inside the pcb
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