Re: The long history of Cinematronics and Vectorbeam

On Wed, 26 May 1999 16:56:31 -0700, you wrote:

>
>> ""Heck, I think he should just build a whole new vector
>> game from scratch - cabinet and all"."
>>
>> This has been discussed from time to time. The design (de)volves
>> into some sort of PC with a vector generator card.
>>
>Yeah. It's just too hard to beat the price/performance you get from a
>PC motherboard. I can't build a 68000 based vector game board for less
>than a PC motherboard-- and the PC motherboard gives lots more "bang"
>for the buck...
>
>> The problem continues to be what to use for a display.
>>
>> As sources for the MPS transistors dry up, there sure seems to
>> be a need for a replacement deflection board design for the
>> existing monitors as well.
>>
>I was looking at that again. I need a yellow "MOSFET's for Dummies"
>book though. I've never had to use them except as current switches
>(like ON/OFF). I do think a vector deflection section with a pair of P
>and N channel MOSFET transistors is relatively striaght-forward
>though.... Given the right MOSFETs-- which seems to be the tricky part.

I looked into using MOSFETs once, the problem I had was how to control
them in the analog mode. They really want to act like a switch. And
the level at which they are in analog mode is very narrow and varies
all over the place even between the same parts off the same batch.

I found a schematic for an audio amplifier once where they used
MOSFETs in there analog mode as the output devices, there was a lot of
circuitry to control them, and they were unable to come up with a
designed that worked without tuning. Each device (there was two, it
was a complimentary output driver) required a trim pot to be adjusted
to the proper "analog" voltage level, to work.

It was rather disappointing.

It makes you wonder if you could not use them in a PWM mode. That
would be very efficient heat wise, but I'm sure the PWM frequency
would have to be very high. But I know they've built audio amplifiers
this way!

-Zonn
Received on Wed May 26 19:26:57 1999