Mk 107 help!

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1

i’ve just built my mk107 kit, and something strange is happening.

when plug in the battery, some LEDs light up, but nothing else happens. when i press the switch sw1, the lights all go out. when i press sw2, no effect happens.

when i unplug the battery and plug it back in, some LEDs light up, but not the same ones as before, sometimes no LEDs come on.

i’ve checked all the soldering and i dont think i have any shorts.

i’ve only built this circuit with 6 of the 8 LEDs, so could the fact that 2 LEDs have been left off be affecting the circuit?

help! :frowning:

2

Check circuit around oscillator IC1.
Leaving 2 leds off should not be a problem.

3

had a look and can’t see any bad contacts or shorts.

bad 555 perhaps? or low battery?

4

after checking again and again, i eventually found that i’d put C1 in the wrong way round.

check ya polarity guys! a simple daft mistake that took me hours to find lol.

by the way, can the mk107 kit be made to run on the first sequence straight after power is connected?

i want just basic chasing lights, but don’t want to have to reset and then start the sequence after switching the circuit on.

5

Happy you found it.
No, operation at power-on is not possible.