Re: Amplifone Design... Wonders me

On Tue, 9 Mar 2004 21:35:41 +0100, "mypearl" <mypearl@dds.nl> wrote:

>Hello Zonn,
>
>Nice to read your extensive reply about amplifone regulation.
>
>
>> No low voltage regulation.
>>
>> I noticed this a long time ago. Every properly working Amplifone I've
>owned has
>> had a less stable picture than every properly working WG6100.
>
>So it is normal to have the image wobble at the outlines over maybe as much
>of 1/4-1/8 of an inch... ???

A 1/4 of an inch seems a bit high. On mine it was just a few pixels, but on a
working WG6100 with a LV2000, I could keep the display stable within a pixel.

>It is SO annoying... the wobble is made up of the difference in X and/or Y
>input frame frequency and the 50Hz (60Hz in US). The amplification factor
>(gain) of the amplifiers is modulated by this frequency. A 53 Hz frame
>screen looks ugly (3 Hz wobble), 50 or 70 and greater frame frequencies look
>better.
>
>
>> The Amplifone's whole reason for existence was price reduction (and maybe
>supply
>> problems with the WG6100 as well). The first thing they got rid of was
>the low
>> voltage power regulator -- they replaced it with a wire. The second thing
>they
>> got rid of was the high voltage regulator, it was replaced by a
>> feroresonance(sp?) design that does not regulate as well as an active
>regulator.
>
>I'm not so sure this was done to make things cheaper.

No it was definitely price. Somebody posted the patent number, a few months
back, on the MC1 coil, and that was one of the big advantages listed in the
patent.

And it is *way* cheaper.

>Star Wars wants to be able to defocus the beam to create some special
>effects. Notice how the enemies laser shots are defocused and therefore look
>really cool and cloudy (in stead of a bunch of lines) such as i.e. Tempest.

You can do that with any standard HV regulator as well, as soon as you try to
pull more current from any HV supply that it can deliver, things will go out of
focus. If they had wanted to do that, it would be easy to add current limiting
to a standard supply. I believe the Amplifone and WG's HV can supply similar
amounts of current. My guess is they are both limited by the amount of current
the HV xfmrs can supply (either because of wire resistance, or core saturation).

>A little history I once heard telling:
>First Atari deviced a HV supply in which a vacuum tube could change the
>focus, but ofcourse this was not feasible for mass production.
>Then they decided they could also overdrive the RGB inputs, causing the beam
>current to go up in such way the HV supply voltages drop and the beam is
>defocused.

The vacuum tube was there to change the focus voltage, not the high voltage:

  http://www.jmargolin.com/vgens/vgens.htm#Star

It's been a while since I've played with a real Star Wars machine, but I seem to
recall that they over drove inputs while displaying the "Long ago, far away..."
message. The letters were out of focus, but there wasn't a lot of blooming.
Low high voltage would cause blurring, but it would also cause major blooming
that would grow and shrink depending upon how many vectors were being displayed.

I remember bad focus, but no really major blooming affects, except for the
explosion which does cause the HV to lose regulation, and there was some pretty
decent blooming along with bad focus.

You can fill me in on how well my memory is here! ;-) (It could also be I was
looking at a bad machine, I've never owned a Star Wars and don't know how it's
supposed to look.)

>A very well regulated HV supply doesn't work well (or too well) in this
>case. Maybe this is why the amplifone has it's kind of regulation... to
>enable 'blurry' vectors.

I don't believe the Amplifone was "designed" for Star Wars, it was also used in
Major Havoc and Quantum, IIRC. It wasn't until after the fact they figured out
how to screw with it's focus voltages.

>> From a manufactures point of view, this made the Amplifone a much nicer
>design.
>> Wires are much more reliable (and cheaper!) than the highly unreliable low
>> voltage regulator design in the WG6100. In the HV section the poor design
>of
>> the WG6100's HV section was also replaced by a wire (ok a coil, but it's
>just a
>> long wire wrap around something).
>>
>> If it wasn't for a manufacturing defect in the Red HV transformer, these
>> monitors would most likely have been very reliable.
>
>While the deflection board is essentially the same as that of the WG61xx
>range... Maybe the TO3 mounting made all the difference...

What seemed to kill most WG6100 was low voltage regulator failure, which the
Amplifone doesn't even have. The low voltage failure could then cause
deflection parts to fail. The LV2000 gives the WG6100 "Amplifone" reliability,
since as you say, the deflection circuits are nearly identical.

-Zonn

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Received on Tue Mar 9 18:45:02 2004