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Help with What To Replace Next on Small Board

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Tony T.

May 7, 2014
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I have a Kitchen Downdraft Vent that's telescoping and lowers into the countertop (GE model: JVB67) and when I touched a wire to the body, I saw a spark fly and it no longer worked. The wire is to the remotely mounted raise/lower button which is just completing a circuit like a simple doorbell does.

I found a resistor burnt out on the board (model: WB27X10704), but the board is no longer available. I replaced the resistor successfully (330 Ohm 1/4 Watt) but the vent continues to do nothing when bench testing it.

What would be a way to test what else went bad OR what is the most likely thing to replace? I'm willing throw a few bucks at some parts since it will be 1000 dollars for a new vent and 300 dollars for a used board on ebay.

The first 2 photos are my board, and the rest are other people's boards (on ebay - no longer available) to help see more detail.

Thank you for anyone's help in advance!

P.S. I know the soldering is bad, I was forced to use an old iron that didn't heat properly; I now have a good iron that works.

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WB27X10704.jpg
 

Bluejets

Oct 5, 2014
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By the look of your "repair" job, I'd tend to say, quit while you are in front.
If you need to replace anything else on that pcb, there will be nothing left usable.
 

kellys_eye

Jun 25, 2010
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The white 6-pin device is an opto-coupler and the burned out 330 ohm resistor was part of the LED side of the coupler. Blowing the resistor has likely blown the opto now so it needs replacing.
 

Tony T.

May 7, 2014
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Bluejets: I can solder fine. I was careful to point out I had a defective iron. I can solder fine; I know the principles and have successfully in the past.

Kellys_eye: Thank you! I'll look them up and try to figure out which one I need. I am a newb with an opto coupler, so if you can recommend the one I need, I would be thankful. But I'll start looking into it to see if I can figure it out.

THANK YOU!!
 

Tony T.

May 7, 2014
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Thank you Delta! Mouser was the only place I could find to order 2-3 at a time. But they had only MOC3012M, not MOC3012. So I took a chance. I looked for a long time and could not find the difference. I just hope it's the same without the "M" on the end.
 

Delta Prime

Jul 29, 2020
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But they had only MOC3012M, not MOC3012. So I took a chance. I looked for a long time and could not find the difference.
MOC3012 has an output capable of 250 volts peak whereas moc 3012 M is ON Semiconductors XM series class; which is capable of outputting 400 volts peak, so you're okay
 

Tony T.

May 7, 2014
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Thanks again Delta - thank you for taking the time to help me. I'll get them in 3-4 days and install it and report back.
 

Tony T.

May 7, 2014
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SUCCESS!!

I replaced the Optocoupler/opto-isolator and it worked! I can't tell you how thankful I am for Kelly's and Delta helping me figure out what to do. It saved me a lot of money!

The pencil style iron I got still would have trouble melting the solder. So I got a Gun! I had to use the super hot gun for a few of the pins, but it worked and I have continuity.

Thank you again!
 

Tony T.

May 7, 2014
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Thank you for your contribution, Blue. I wish you well with your efforts.
 
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