[sdiy] Integral scope on VCO

[Magnus Danielson]

From: Tony Clark <clark at andrews.edu>
Subject: Re: [sdiy] Integral scope on VCO
Date: Tue, 13 Apr 2004 18:30:16 -0400 (EDT)
Message-ID: <Pine.SOL.3.91.1040413181810.3698D-100000 at edmund.cs.andrews.edu>

>    Hi Thomas,
> 
> >  I'll have to experiment a bit with this, maybe implement a simple trigger
> > circuit and beam blanking... It gets a bit interesting, since the CRT
> > needs a 500V focus voltage and the deflection amp outputs must be
> > elevated to 500V. The PSU for the whole CRT and deflection amps has to be
> > at least 800V, or more like 1000V, with multiple 'taps'. It'll get tight
> > in there, with transformers and HV capacitors etc.
> 
>    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!

CRTs don't require huge current really, but the electron beam is indeed a
current which needs to be balanced, or it will pull down the voltage. The 2AP1
tube is probably quite close to what you got (don't have the Philips stuff
here, but a friend has the full Philips suite of databooks) and it is fairly
easy to hook things up. My sources here are from.... HRM! 1945 and 1948!

The traditional way of generating these voltages is to span up the 1-2 kV
needed and divide down and burn of the intermediary effect. A more modern way
might be to do a few small switch-supplies which one regulates to the target
voltage. They shouldn't need to be very complex really. Hmm... interesting
concept.

>    Bitten more than once,

Once bitten by the bug, then always jitterbugging! ;O)

Cheers,
Magnus