Re: Vector Monitor HV power...

On Mon, 1 Dec 1997 17:10:44 -0800, Clay Cowgill <clayc@diamondmm.com>
wrote:

>>couple of things
>>
>>unless you can find an output winding on the atari power supply
>>assembly, you'll need an isolation transformer on the AC line.
>
>True.
>
>>you will have to experiment with the LC value of the primary of
>>the chosen HV transformer to get it back in resonace without
>>the horizontal deflection coil in the circuit, or adjust the
>>osc frequency up (not a big deal since you don't have to run
>>at 15khz, in fact, it would be better (noise wise) if you were
>>supersonic)
>
> From the look of it, I'll just be replacing the HOSC output from the
>monitor's "control" IC with a similar signal from a 555.
>
>>the HV on vector monitors is a few KV lower on vector monitors
>>than raster monitors
>
>That's actually a good thing, IMHO. I run my monitors several KV lower
>than the manuals say anyway with seemingly very good results...
>
>>you didn't mention if you were going to make this a closed
>>loop HV supply (with HV regulation)
>>HV regulation is a GOOD THING.
>
>The Wells Gardner/Amplifones didn't do that did they? Wouldn't that mess
>with the Star Wars explosion effects?

Wells Gardner did regulate the output, based on feedback from the 180v
supply.

Amplifones use a completely different way of regulating their HV.

At a company a few years back, we were using some tuned transformers as
the basis of our computer power supplies. I can't remember what these
things were called, but the effect was by running the transformer with a
big capacitor on a winding on the output, the transformer would resonate
, at 60hz, into total saturation. At that point, for a pretty broad
range of values (70v to 190v) changing the input voltage had no effect
on the output voltage.

The Amplifone seems to use a very similar circuit. By running the
voltage through that *magnoresonator* or whatever that coil looking
thing is, combined with a specially wound HV transformer, they seem to
keep the transformer/magnoresonator in saturation. This keeps a constant
value on the output of the HV even with current usage changing on the HV
supply. I don't even pretend to understand it, though if that
*magnoresonator* thingy were describe better I'm sure the circuit could
be described with some simple LC math. Either way, the amplifone's HV
is also regulated.

The Amplifone does fall out of regulation during the explosion scenes.
If you look at the +/-24v regulators used to regulate the inputs you'll
see they are bypassed with 50 ohm resistors. During the explosions, the
7824/7924 could not supply the amount of current needed. These resistor
supply the additional amount of current during current peaks, though
when they kick in, regulation is lost.

-Zonn

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Received on Mon Dec 1 17:35:02 1997