tr-909 schem's

[WeAreAs1 at aol.com]

In a message dated 10/28/00 2:47:14 AM, alan.p at clear.net.nz writes:

<< I printed the 909 voicing board out (taping the separate sections
together....) and the long trigger lines and outs sometimes have filled or
hollow shapes on them, like squares and triangles, like in (O 13-14) Do
these indicate that other lines with similar markings are connected? >>

Yes, the lines with identical markings are connected.

<< Also, is the 4174 IC a 4040? What is the 4520? >>

The 4174 ia hex D-type storage register.  4174 was the older number used for 
that part, but today, it is almost always referred to as a 40174.  It 
definitely does not have the same function as a 4040.  The 4040 is a 12-stage 
binary ripple counter.  These are often used to clock sequentially through 
the addresses of 8-bit sample ROM's, as is done in the Oberheim DMX, DX, and 
the old LinnDrum.  (the 909 may also use them to clock through the addresses 
of its hi-hat, ride, and crash ROM's - I can't remember for sure right now)

<< I figure that the
HN61256P-C4x is the eproms containing the sample data for hihat, crash, and
ride. Is that right? >>

Mmmm... HN61256 sounds more like a part number for a Hitachi static RAM chip, 
in which case it would be for storing the 909's pattern and song data.  I 
don't have the schematics handy, so I'm not sure.  I'll bet that Colin Fraser 
knows... Colin?

Michael Bacich