Sequential Split-8 repair

[Harry Bissell]

Ooooh I know...I know....

The 5 volt regulator is a "dirty trick" to get more current out of the
regulator... so it will either run cooler, live longer, or use a smaller
heatsink...
The current carried by the resistor doesn't have to go through the
regulator... It works as long as you know the load... including that the load
can't be "open". This is where the trick fails.  This is often done in the
"Creative Engineering Dept... where we turn 'bugs' into 'features'..."

:^) Harry

Barry L Klein wrote:

> Anyone have experience repairing/using a Spit-8?  I've got one in which
> the pitch bend wheel doesn't act right.  As you raise the amount the pitch
> tracks ok for awhile and then pops up about an octave.  You see this pop
> in control voltage to all the 3394's(pin 2).  The voltage goes through a
> 4051 and then gets distributed to a dedicated 4051 for each voice.  All
> voices do the same thing and the signal that gets sent to each one's
> 4051operates linearly.  So why the pop out of each voices 4051?  Weird.
> There is a negative supply voltage set by a LM317/337 at -6.6V, which
> really measures -6.4V...  I was thinking of tweaking that to see if it
> made a difference.  I'm planning on forcing the 4051 selects to select
> just this switch path to debug it and that entails removing and socketing
> a chip to gain access to the lines etc. - a little messy so I thought I'd
> ask if someone here had any experience with this before.....
>
> Also one of the 5V regulators has a 220 resistor tied from its output to
> its input.  With no load, the output raises up to 7V!  Why did they do
> this(its designed in this way)?
>
> There was no service manual made for this synth.  Only schematics, which I
> have portions of, and an operations manual, which I don't have.
>
> Barry