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AEC Chaser only lights first LED. Newbie needs help

geezer67

Oct 22, 2019
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I have built two of the AEC chaser circuits according to their directions and neither one works. The first LED lights up and that's all. Here is a pic of the completed chaser. Can anyone advise what's wrong? I have a third one I can build since they are only 7 bucks apiece.
 

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Audioguru

Sep 24, 2016
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The instructions do not show a schematic but says to be sure that the polarity of C1 is correct. Maybe yours is backwards. The white line on the side of the electrolytic capacitor is its negative wire side.
If you touched the battery backwards to the battery connector even only for a moment then the ICs might be destroyed.
Maybe the kit people used the wrong ICs (the small one is an LM555 or NE555 and the large one is a CD4017) or used fake Chinese ICs.
 

geezer67

Oct 22, 2019
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Yes polarity of the capacitor is correct, and I got it working but I am not sure why its working. I shorted across pins 6 and 7 on the 555 timer and it works. The problem is now, that the other two of these I built, will not work even when its shorted. completed chaser.jpg solder side 1.jpg
 

Audioguru

Sep 24, 2016
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When a 555 IC is used as an oscillator then the minimum resistor value for the resistor from pin 7 to the positive supply is 1k ohms. Your trimpot can be turned so that this resistance is zero which might destroy the 555 IC.
The datasheet always shows a resistor from pin 7 to the combined pin 2 and pin 6. Its minimum value is about 1k and its maximum is a few Megohms.

I think your KA555 ICs are cheap Chinese fakes.
 

geezer67

Oct 22, 2019
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You might be right cuz I don't know. This chaser comes this way from All Electric. I don't know if this will help, but here is a picture of the circuit board as it is sent.
 

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Audioguru

Sep 24, 2016
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In the reviews for the chaser kit one person needed to add a supply bypass capacitor (which is mentioned on the datasheet of an LM555) to make it work properly and a few people said that their soldering probably fried the chips. Cheeeeep soldering irons that get too hot??
 
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