[sdiy] TR-7x7? (was Re: Proms)

[Colin f]

> -----Original Message-----
> From: Dan Gendreau [mailto:gendreau at rochester.rr.com] 
> Sent: 26 September 2002 2:01
> To: Colin f; Drew Smith (mux)
> Cc: synth-diy at dropmix.xs4all.nl
> Subject: RE: [sdiy] TR-7x7? (was Re: Proms)
> 
> I have the service notes here... my copy of the schematics 
> didnt pick up red
> very well, and all the tr727 notes on the schematic were in 
> red, so I cant
> speak to the differences between 707 and 727. As far as I can 
> tell they are
> identical.

I'm in the same boat - monochrome photocopies only, with notes that
differences are in red.
Whether they are significant or not, who knows...

> One thing you should be aware of is that Roland jumbled up 
> the ROM address
> pins to improve PCB layout or obfuscate the rom data or both.

They did the same thing with the hihat and cymbal ROMs in the 909.
I extracted the data from the 909 ROMs for my clone, and wrote it to
EPROMs using the normal JEDEC pin assignments.
In order to provide replacement ROMs for real 909s, I wrote a little VB
app that will transform a binary ROM image using a mapping of the
required address and data lines. I can mail it to you if you're
interested.
It allows suitably envelope processed 8 bit unsigned pcm files to be
converted to ROM images for the 909 cymbal circuits.

Colin f