Hi Bakis,
Thanks for the info.

> if the mod is a resistor and a capacitor in the a155
> control board,then this is the mod i was telling you
> about...it's the mod for letting you clock the a155
> from an imperfect clock pulse(with not sharp
> edges).also,with this mod ,you can step manualy the

This is part of what I was after - there is also a wire from the
control board to the trigger board (it inhibits trig 1 and 2 under
some conditions), and I was wondering if they were both part of the
cure for some problem. However, that you say the res & cap were to
help it with poor clock pulses raises a few questions. I wondered if
it was for something like this, so I ran a quick simulation of that
part of the circuit, and got the distinct impression that it actually
made things *worse*, which made me think it was for some other
purpose, and that if it was then hopefully the degradation of the
clock pulse would still be acceptable! (The simulation _did_ show
that the clock stops running at some point due to the mod, and tied
in very closely with my measured value - around 800Hz.) I shall look
at the circuit some more, I may be able to figure it yet!

Tim

> sequencer from the tiny step button more
> properly(without almost jumping
> steps...).but,also,this mod stops the a155 from
> running in high audio frequencies!even if you clock
> the a155 from an a110 you will notice that,the a155
> can't run above a certain speed limit(which is rather
> low!)all these are valid only if we're talking about
> the same mod,though....
> by the way,i removed this mod from two of my a155's
> because i want them to be graphic vco's too!
> bakis.