Howdy, I am fairly new to this forum and returning back to electronic tinkering after a fairly long hiatus, so I am a bit rusty. I thought I would ease back into hobby electronics starting with a couple easy circuits and some kits and work my way up. I managed to build a couple amps, LED circuits and a color organ, however, the kits are being little buggahz. I couldn't get one of the amp kits to quit squealing, which I finally gave up on, and now a LED chaser kit is keeping me up at night. I bought this kit:

http://www.allelectronics.com/make-a-store/item/AEC/LED-CHASER-KIT//1.html

I have asked for some help from the place I bought it from but have yet to hear anything back from them.

I want to start learning more about 555 timers and 4017 decade counters. And this seemed like a very basic circuit but for the life of me I cant figure out why it wont work right. When I connect the power, It will run through the sequence once and then get "stuck" alternating between the last two lights (the LEDs connected to pins 2 & 3)

The only mod I did to the circuit was attach the LEDs to 5" wire leads. I also had to reconnect some parts of the circuit board that I had to accidentally scraped away thinking they were solder bridges when I was trying to trouble shoot the problem. I got the circuit back from not working at all to the original state of running one sequence before getting stuck on the two LEDs. I would like to figure this out on my own but I am stumped and could use a nudge to help get me looking in the right direction. I have already checked the polarity of my caps and resoldered every connection point. I am including a picture of the board and components. I know the 555 chip is not the problem because I was using it in a flasher circuit for a couple days before building the chaser

Any help or comment is appreciated,
Cheers,
Chongz

 

what are the component numbers and can you make the pic a bit clear.
no matter ...555 and 4017 ....the common chaser.

We'll need clear pics to find where the problem lies. buddy

 

Does this photo help to clarify?

 

do you know where the reset pin is for the 4017

 

should be pin 15 right?

 

is reset connected to ground...i can't make it out due to low resolution

 

its not directly connected to ground, it goes through both caps. But ground is ground right? I can take better pic if it will help

 

Pins 8, 12, &15 all connected directly to ground between rows of pins; other side of pin 15 then goes to 555-1 & - cap. I can find no problem. Lead extensions on LEDs should be OK. Maybe a bad 4017? On second look-- looks like there may be a solder bridge between p-8 & p-10, should be two 1/2 mm traces going in oposite directions fromp-8 & p-10.

 

Thanks so much for the help. I will take a closer look a p-8 and p-10

"should be two 1/2 mm traces going in oposite directions fromp-8 & p-10"
Didn't quite follow this though. "1/2 mm traces"?

 

I believe this is about what the bottom of the 4017 socket looks like. Narrow trace guestimate 1/2 milli meter, wide X3 or 1.5 mm. Space between p-8 & p-10 traces about one narrow trace, easy to bridge. Maybe a little less solder could be used in future.

 

[ed]
Nevermind

 

There should be no connection between pins 8 and 10. Pin 10 is one of the LED outputs. I would try adding a 100nf capacitor between pins 16 and 8 (or if easier, between 16 and 15 or 16 and 13 - pins 8, 13, and 15 are all grounded). I have found that the 4017 is sensitive to glitches.
/mike

 

Thanks again for taking the time to help me solve this puzzle. I have cannot see any solder bridges between any of the traces and all looks good between p-8 and p-10. I have another 4017 and 555 ic coming in the mail so I may try to breadboard this circuit and see if I can get it to work before replacing the 4017 on the circuit board.

I guess there is the chance that I fried one of both the chips when soldering. However my soldering iron is has a pretty small wattage. Are these chips prone to being fried easily? Any tips on soldering them?

I will let you know what happens when the new components arrive.

Aloha

 

a few soldering tips.
Use low wattage irons, temperature controllable is highly preferable.
U should Solder in less than 10 sec max per given IC pin at no more than 300°C. Period. no exceptions here.

 

Thanks for the tips R!f@@ I will keep them in mind next time I fire up the iron

 

I had some issues when modifying that same kit some time back. Several members here chimed in with very useful advice. For some reason my computer has lost the ability to copy/paste links today, but if you look up my threads you'll find the one that deals with this kit.

 

Is this the one? - http://forum.allaboutcircuits.com/showthread.php?t=22646

 

Is this the one? - http://forum.allaboutcircuits.com/showthread.php?t=22646

Yep, that's the one. Lots of good advice in there.

 

So I replaced the 4017 and now only the LED coming out of p-5 lights up when power is connected. The sequence doesn't run at all the LED comes on and that is all? Any suggestion on what I should try next?

 

Nevermind my last post I accidentally replaced the 4071 with a 4026. So I am ordering another 4071 as a last effort to salvage this thing