[sdiy] Integral scope on VCO

[Theo]

On second thought, maybe put a small 220V transformer in reverse first
(EE20=22x23mm).
Its outside the specs but using 12V to get 530V from a 220V/5V transformer
should work ok.

Theo


From: Theo <t.hogers at home.nl>


> ?? 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
> >
>