[Coco] Midwest VCF

gene heskett gheskett at wdtv.com
Tue Sep 27 12:45:33 EDT 2011

On Tuesday, September 27, 2011 11:55:23 AM Mark Marlette did opine:

> Gene,
> Do you still have the Elf?

I wish, but no Mark, there was only one purchased, based on a presentation 
I did to the GM at KRCR, one that I saw as a problem that was hurting our 
commercial production.  I didn't even get to where I was talked out before 
Dick said lets do it.  I guess I must have made a good case out of what was 
200% blue sky at the time.

So I bought the single board, ($250 IIRC) spent about 6 weeks playing with 
it, seeing what it could do (remember I'd never seen anything more than 
better calcs like the TI SR-51 at that point), and getting an idea of how 
much I'd have to do in hdwe that it couldn't, and then miss-cued on the 
video because I first used a video clock chip but the characters were way 
too small, so I had to stop and design a board to make big characters, 
which took me 3 or 4 days, then a couple of weeks to collect the stuff and 
make it, using an 74ls154 (151?  Memory is hazy now) to select the pixel 
left to right, and a diode matrix to construct the figures from each nibble 
of a byte.  Decimal point hard coded.  The memory board, and Quest was 
selling a cabinet that resembled a mini cash register, but the s-100 & I/O 
stuff occupied the overhead where the registers display would have been.  
The left to right scan was timed by house HDrive & a 555 to adjust it for 
centering, ditto for the vertical centering, and some dividers so that when 
the vertical 555 timed out, it loaded the first data byte into an 8 bit 
latch, and for the next 3 scan lines that was repeated, then another byte 
was fetched (by dma) which was the next 47 lines, the vertical bars of the 
top half of the character, then another fetch at the 50th scan line for the 
center of the char, line 53 fetched the vertical bar data for the bottom, 
displayed for another 47 lines, then line 100 was the bottom, and a 6th 
null byte was fetched at line 103 to stop the bottom of the character.  
Those line numbers are from the end of the 555 cycle, so it could be 
centered both ways.  That was sent through a cmos hex buffer all in 
parallel, and mixed with house sync, and insert recorded from 9.59 seconds 
before 1st video, to 2.0 seconds before first video, so a 5 second preroll 
could be done, both by hand or by the station break machine.

I'd probably buy one on the spot if I could ever run across one of them, 
I'd like to build another just for my own museum.  I already have the EDISK 
I made for WDTV back in the 80's which was used non-stop till about 6 
months before I retired in 2002.

> It was my first computer, learned how to hand assemble in high school.
> :)

Yes, with the RCA manual (MPM-201c, I still have mine) in hand, it was an 
excellent teacher.
> Worked for an Energy Management System firm on the manufacturing
> side..They used the 1802....
Its still used in oil & gas exploration as its radiation resistance allows 
it to be used downhole using alpha scattering techniques to find gas and 
oil deposits.  We did have a company here in Weston that used that, but the 
hot sources had to be handled with care because they were really hot, and 
eventually their 'brain' on that stuff left for Florida and some TS 
military stuff where he could get paid 5x for less exposure.  The local 
company couldn't find anyone to replace him at a price they thought was 
good (damned MBA's), and had to reinvent themselves as a normal well 
service company.

The brain? (he may have had an IQ in the 120's, no match for me at the time 
20+ years ago) tried to reach back up from FL and hire me 2 or 3 times, but 
I'm not a fan of the FL environment & kept asking for details he couldn't 
supply because of the TS thing, so it never led to an actual on site 
interview.  Just as well IMO, I was happy doing what I did best here.  I 
was by then 'settled in' here & married to a local school teacher.

> Very cool when in high school, engineer was great, taught me a lot.

I too have had some interfacing with some that weren't afraid to teach, 
good lessons learned.

Cheers, gene
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
  "Professional certification for car people may sound like an
  oxymoron." -The Wall Street Journal, page B1, Tuesday, July 17,

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