On 2008-11-08, IanW wrote:
"Jasen Betts" wrote in message
...

I increased C1 to 470nF which slowed things down a bit, then took the 4017
out and wired up that jumper and exactly the same problem - all 20 flashing
on/off at the same time. In fact even without the jumper!

my guess is you've got some of the transistors round the wrong way.

However, I found that I had wired R11 from the base of Q11 down to pin 11 of
the 4047 instead of pin 10. So now 10 flash on simultaneously, then off,
then the other 10 flash on/off.

hehe progress!

cool!

that should make only 2 of the leds work if it doesn't there's a
wiring problem somewhere between the 4017 and the transistors.

if it does it's possible the 4017 has bee damaged.

Nope it stays as 10 on 10 off, not just 2 LEDs. Rest of the wiring seems
fine.

the 10 led-pair transistors (Q1 to Q10) should be off with the 4017 removed
so there's something wrong there. as they are conductiong with no base
current present. tripple check them.

Try removing Q1 that should make two of the leds stop lighting up,
if not there's a short circuit on your board. if it does there's
something wrong with Q1, (wrong way round, or damaged, or both)

my guess is you've got the base and collector swapped, if that's the
case it won't have damaged the transistors.

when you get it the right way round a jumper from pin 3 to 14 of the
4017 socket will control the first 2 leds,

when you fix that problem then do the same to the other transistors and
then plug the 4017 back in.

Well, this is the nearest I've got to chasing anyway

double cool! stay happy!

Jasen