[sdiy] Integral scope on VCO

[Harry Bissell Jr]

Thgat would take a HELL of a lot of diodes and
capacitors... and some pretty high voltage ones at
that.

That's why the voltage doubler, tripler trick is not
played often.

I would NOT try the scope in a VCO project. Keeping
the
EMI from the scope from interfering with the VCO will
be the major design challenge.  I'd probably get one
of those tiny scopes that NonLinear Systems used to
make...
and just modify the package to add it to the synth.
The
metal box, shielding etc are all in place, and its
sort
of instrument grade already !

I agree it would look cool, and possibly be useful.
Prlly not as useful as an external scope....

H^) harry



--- Theo <t.hogers at home.nl> wrote:
> ?? Assuming you got some (12V?) AC hanging around,
> won't a simple diode/capacitor cascade do the
> trick??
> 
> Theo
> 
> 
> 
> ----- Original Message -----
> From: Thomas Dunker <dunker at invalid.ed.ntnu.no>
> To: Tony Clark <clark at andrews.edu>
> Cc: <synth-diy at dropmix.xs4all.nl>
> Sent: Wednesday, April 14, 2004 1:07 AM
> Subject: Re: [sdiy] Integral scope on VCO
> 
> 
> > On Tue, 13 Apr 2004, Tony Clark wrote:
> >
> > >    It's quite possible to make very tiny high
> voltage supplies for your
> > > application.  I just finished designing just
> such a thing for a product
> > > my company is making.  I was able to come up
> with a design that
> > > will generate a good 1200V DC (approximately)
> and fit in a 2x2x0.5
> > > space.  It runs on 12V at 120mA and the best
> part is the total parts
> > > cost is less than $10.00 (in quantity, probably
> about $15.00 for a
> 1-off)
> > >    Don't know what kind of current the CRT
> requires, but the power
> supply
> > > will definately give you a good zap!
> >
> >  As far as I can tell from the data sheets on the
> CRT, the beam current is
> > virtually in the microamps range, but I also need
> a reasonably high
> > voltage supply for the deflection amplifiers (need
> about 250V pk-pk for
> > full deflection on either axis) and it seems most
> realistic to get the
> > supply voltage for these amp stages from the same
> supply. The deflection
> > amps can be high impedance things so don't really
> need to take a lot of
> > current. I just emailed a Norwegian ham who built
> a scope module with this
> CRT,
> > so it'll be interesting to find out how he did the
> deflection amps. I
> thought
> > about using diff stages with 12AX7 type tubes
> which work fine at 0.5mA per
> > section, so two diff stages would typically draw
> about 2mA. But for the
> > sake of saving space it would be nice if I could
> use transistors in the
> > deflection amps. I don't know precisely how that
> would work out in terms
> > of current consumption. I may have to sink some
> current into a voltage
> divider
> > and some pots and things on the same supply,
> unless I can get a HV
> > transformer with sectioned secondary and make a
> stacked supply. In any
> > case I will be needing something like -50V, 0V,
> 500V and 800V taps.
> >
> >  It's not like I don't have high voltage
> transformers in my stash, but
> > they do take up a lot of space (relatively) and so
> do high voltage filter
> > caps when they have to take care of 100Hz ripple
> current. It's cool when
> > it's a classic tube amp for the stereo where size
> and weight doesn't
> > matter (to me, anyway) and one can liberally build
> pi filters with 10
> henry
> > iron core chokes and that sort of thing, but this
> is a little different...
> >
> >  I was looking at some high output voltage DC-DC
> converters in Farnell's
> > catalog, but they were far too wimpy on the
> current for my purpose. We're
> > probably looking at a 10-20W supply, whereas the
> module available from
> > Farnell was good for 1 watt...
> >
> >  A buddy at work says I'd probably have to use a
> flyback type converter if
> > I want to go that way. I'm just a total idiot when
> it comes to switched
> > power supplies, since I've always avoided them in
> audio apps, but for the
> > scope they'd sure come in handy. It would be a
> good excuse to learn a
> > little more about them... I guess if I need
> multiple voltage taps I could
> > feed like three separate ferrite core transformers
> from the same switcher
> > thing? Oh, and it would definitely be most
> convenient for me to make an
> > AC/DC supply with 230VAC input at this kind of
> power, otherwise I'd eat
> > away at the synth's low voltage supply's available
> current real fast.
> >
> >  Can you say a little more about the type PSU you
> had in mind?
> >
> > Thomas
> >
>