Update - Circuit problem: Can anyone figure out what may be causing this project to only work half way?

Ok, I have a recently built prototype of a circuit I was going to publish, but it is not working exactly as planned. It is not that it is not working at all, but it is acting strangely.
What is happening: pairs are blinking alternately, when they should be blinking in sequence. Can anyone see a fundimental flaw in my drawing, or is it a possible soldering error. Opinions and insights welcome.

PS: the included video is the first one I have even edited too (I forgot that the camera picked up sounds, and I had grunted, and verbally expressed surprise and it sounded inappropriate, so I edited it out.)

PPS: I believe I have to declare FAILure on this one, at least for now. Sorry....





Picture of Update - Circuit problem:   Can anyone figure out what may be causing this project to only work half way?
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gmoon8 years ago
Here's a guess as to the behavior... There are four stages, all "identical." Their tendency is to work in pairs; each wants to the inverse of the stage before. There is no stable condition here--once powered up, they want to either charge or discharge those capacitors, and to immediately restart the cycle. Since there are small differences between each component, the oscillation begins at a random stage, and then each pair starts to do it's thing. Try disconnecting (or grounding) the base of the first stage will create a stable state, then connect to initiate... Each stage still wants to be the opposite of the preceding stage, but maybe...
Goodhart (author)  gmoon8 years ago
Thanks. Yeah, the person that showed me a similar schematic said that jumping the first capacitor momentarily would stabilize the blinking into sequence, but that appears to do nothing, which led me to believe in a possible cap failure. I will try what you suggest as nothing else has worked so far.
Goodhart (author)  Goodhart8 years ago
Notice that the pairs alternate (1 and 3 fire, then 2 and 4).
Goodhart (author)  Goodhart8 years ago
It altered the flash sequence for a moment or so, but then things went back to normal alternating flashes, as soon as the jump was removed. It didn't seem to matter how long or short I kept it there, either.
gmoon Goodhart8 years ago
There's a circuit schematic that's almost identical here, which describes operation. Possibly a higher

However, it uses 5V filament lamps which draw 200mA. Assuming your components all check out OK, 100 ohms for a base resistor would seem too small for a 20mA load (ballpark LED load.)

Maybe that tends to bias ON. Once it's running, alternating behavior definitely looks like a stable condition.

It also describes starting the circuit by "jumping" one of the caps...

Regardless, a multi-LED chaser is pretty cool, too.
Goodhart (author)  gmoon8 years ago
Oh, so that is where this is from originally....thanks. So, do suggest I increase the base resistance?
gmoon Goodhart8 years ago
It's a guess. A smaller load (1/10) with a bipolar transistor calls for a higher value base resistor...
Goodhart (author)  gmoon8 years ago
I will have to try that then, maybe a 1 k resistor to start with?
gmoon Goodhart8 years ago
Sounds like a plan...
Goodhart (author)  gmoon8 years ago
I never got it to work properly.....too much futzing with the parts even after installing pots.
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