[sdiy] Integral scope on VCO

[Steve Allen]

Hello,
 I'm not sure if this is even close to what you might want to try but, here goes.
I remember years ago taking an old TV set and pulling the deflection coil off the tube but not disconnecting the wiring to it, and tying it up in a safe place inside the tv. I got another deflection coil from another old tv and hooked each side to the output of a stereo amp.I put the whole thing back together, turned on the tv and there it was, a dot in the middle of the ole screen. Turned on the stereo, put on some ELP and Damn, it was pretty cool. Didn't take much work and my buddies commin over to watch the neat patterns on this "invention". Don't remember much after that, cept mom yellin about the smoke in the basement.
 With all the monitors and such at the junk yards, could be a simple way to do a dedicated 'scope for sound graphics.
 Oh, well, just a thought, back out to the garage where I'm looking into plating aluminum with gold!
 
 Steve.

Magnus Danielson <cfmd at bredband.net> wrote:
From: Tony Clark 
Subject: Re: [sdiy] Integral scope on VCO
Date: Tue, 13 Apr 2004 18:30:16 -0400 (EDT)
Message-ID: 


> 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
		
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