[sdiy] I love (hate) sequencers, part deux (read: HELP!)

[Peter Grenader]

Peoples,

I have a little problem that I must take to the masters here:

I had a dream of ending my module DIY'ing with a doosey - building a working
replica of the Buchla 200 16 x 4 sequencer.  (I'm stopping only because I am
out of room in my present cabinet and as soon as I figure a way to get two
into my tiny studio, well..watch out).

I've had some dazzling luck with this functional replica, as it seems I've
got everything figured out (including my beloved VC direction input)
accept...I can't figure out how to set the start point before step 1.

Now mind you, I am not using the discreet components Don did  -and- I'm not
using PICs, either.  I'm going the 4516 into the 4051 route.

I understand that the secret of a setting the start point is the preset
inputs of the 4516, and believe me, I've got those fully incorporated with
the VC direction circuitry.  My problem is, how do I tell the counter to
advance once I tell it to go to a certain start point other than step 1 at
reset?

I am planing on having 16 ON-OFF-ON switches (one for each step).  Flipped
up, and it will create a programmable pulse string at a summed output (not
part of the original Buchla design) consisting of ta combination of the
other switches also in the up positionl (they will be running through an AND
gate with the input clock so that consectutive pulses won't read as one).
Flipped down, and I want that to set the start point of the sequence.

So, I put the output of those switches into a 74C175 and I get four bit
binary coming out - that goes into the preset inputs of the 4516 counter
(master clock).  How do I now turn this preset OFF once it does its job so
that:

A)  It will again start it's sequential advance from that preset point

B) I won't lose a beat in the process, regardless of the speed of the
sequencing at any given time.

Sorry for the long posting.  Any information you could share on this would
be VERY helpful to me.

Thanks,

Peter