> I just got an a155 fixed (which I can confirm is working properly
> on its own),
> and carefully connected it to the a154 (from here
> http://img846.imageshack.us/img846/1517/a154a155connexion.jpg)
>
> I get strange behaviour - it jumps around steps 1 and 2 twice
> then 7 and 8 twice. Both were bought a trade forum, the a155 was
> cheap as it was broken and I just got it fixed, now I'm wondering
> if the a154 might be faulty
>
> Does this behaviour sound familiar to anyone
>
> Thanks

Provided that the A-155 is fine it looks like a faulty A-154. It might be a
short circuit between address signals or an address signal which has a fix
level where it should change the state. I'd recommend to double check the
wiring between the A-154 and A-155. If this is OK maybe the address signal
level shifter (ULN2004) or the triple analog switch are faulty (CD4551).
Difficult to say from the distance what is wrong.

Best wishes
Dieter Doepfer