[sdiy] ETI447

[Rönnberg Niklas]

It seems that you're right. I past the electronic store at work yesterday
and found three 4049 of the old (?) version, and now it works just fine!
Just some more adjustments and then it's finished! It's the old phaser
project, but doubled (12 stages selectable) and a mixer added.

I will probably put some pics and sound samples on my page, and send you an
email.

Thanks for all help!

/Niklas


-----Original Message-----
From:	Colin Hinz [mailto:asfi at eol.ca]
Sent:	Thu 7/8/2004 8:49 AM
To:	Synth-Diy
Cc:	
Subject:	Re: [sdiy] ETI447
On Thu, 8 Jul 2004, Paul Perry wrote:

> At 07:46 PM 7/07/04 +1000, Ken Stone wrote:
> >>I have some questions about this circuit. I think that the use of IC9,
a
> >>4049 CMOS, are quite smart, but why are pin 16 connected to zero
reference
> >>voltage?
> >because the chip is not being used as a digital chip. It is being used
as a
> >row of FETs. (a case of using it in a way it was not designed to be
used)
> >
> And not only that, some ETI synth stuff from the same time, would only
> work if you used the SAME CHIP MAKER as they did.
> Which is what can happen, if you are usign stuff out of data sheet range
;D
>
> Enven 'simple' things like input protection schemes can make a fatal
> difference.

Absolutely. I remember seeing an ETI parts list which specified specific
manufacturers and IC suffixes. Can't remember the project, though :=)

And does anyone remember the original Apple II motherboard, with its
amazing hodge-podge of logic families, carefully chosen to keep the
signal timing under control? It sure did work, though -- even the
"clone board" that I hand-assembled from scratch, using ICs I'd
scrounged from hither and yon, gave the friendly beep the first time
I powered it up. (And a darned good thing it did, too, as all I had
for debugging digital logic was a logic probe.)

- Colin Hinz
  Toronto, Canada

PS: in industry, a "bill of materials" will indicate specific devices
(manufacturers as well as complete part numers down to the "tape and
reel" specs) ALL THE TIME -- neither the purchasing people nor the
production people are expected to be able to make sensible
substitution decisions. That's where component engineering comes
in -- a thankless job if there ever was one.