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Hi, I tried this circuit & it failed the first time. That try was the result of following the schematic, verbatim. For example, the line from the 100k resistor on first chip, running to pin 8 on the second chip. It was broken where it crossed pins 4/8 on the former chip, clearly indicating no...

Just tried this circuit w/ a 2N3904 transistor & a 47k resistor (since I had no 33k's). Then I was looking @ talkingelectronics.com & they showed how one could add a driver transistor to the output of the 555 to drive a lamp. Well, I had some KSC2500's on hand, so I connected the base of one to...

I built this circuit & it worked the first time. Used 2N3904 transistors & four blue LEDs, so I replaced the 470-ohm resistors on the latter two w/ 4.7k's (they were too bright). But what is the purpose of 470's going to ground off the bases of the transistors? I mean, the circuit seems to work...