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From: "Michael A. Terrell"
Subject: Re: Nice power supply - cheap
Date: Fri, 08 Nov 2002 18:11:26 -0500
Organization: Have you seen my bench? No, really! Where is it?
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Stephen Shaw wrote:
> On Sat, 02 Nov 2002 20:32:54 -0500, Michael A. Terrell wrote:
> > Sam Goldwasser wrote:
> >> Winfield Hill writes:
> >> > Yes, those came from the old days of TTL logic that needed horrendous
> >> > amounts of current at 5V. I got 'em cheap for a 1000A 10V source we
> >> Exactly. :)
> >> > needed (use 10 of the 200A units in series - parallel), then gave in
> >> > to others who decided to just buy two 875A HP programmable supplies.
> >> Well I guess if the grant is running out and there's still money to be
> >> spent..... ;-)
> >> --- sam | Sci.Electronics.Repair FAQ Home Page: http://www.repairfaq.org/
> >> Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
> >> +Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
> >> | Mirror Site Info: http://www.repairfaq.org/REPAIR/F_mirror.html
> > Sam, I used to do maintenance on a Vital Industries "Squeeze Zoom"
> > video effects generator that had a three phase 208 VAC input, 5 VDC 1000
> > Amp power supply, plus several other supplies. It powered a full six
> > foot rack of boards to do digital video effects to NTSC video for a TV
> > broadcast control room. It was full of 4K X 1 1000ns ram, and ran with
> > a Z80B processor to do real time video effects. What a monster! Almost
> > one full card cage of memory boards to get 768 K of memory to store two
> > fields of video and chroma information. I'm glad I don't have to mess
> > with it anymore.
> How on earth did you find a faulty RAM in amongst that lot? From what I
> remember early RAM wasn't exactly reliable.
> > Of course, a couple hundred amps at 10 volts is enough to start your
> > car engine on cold mornings.
> Mail will bounce use : stephen (at sign) apple2 (dot) org (dot) za
> It takes 42 muscles to frown but only 4 to reach out and slap someone
It wasn't any fun. First, you could see the bad memory in the
picture. The memory was so slow that four boards were interleaved to
consecutive addresses, and a chart showed you what small areas of the
screen each board covered. A dead board would cause a checkerboard
pattern on an area of the picture. The cards were identical and the
chassis wiring determined the areas where a board was in the memory map.
The memory cards were hot swapable so you would pull the suspect card
while watching a video monitor to make sure you had the right board.
Then you would plug in an extender and the bad card and look at the data
and address lines to see if you could find the bad DRAM. Most of the
time it was easier to find a bad chip with a fingertip. A cold chip was
obviously dead, but the gray ceramic DRAMs ran hot when working, and
part of the time a bad one was slightly hotter. The chips were already
obsolete, so you didn't replace any you didn't have to. it generally
took a half hour to find and replace a single bad chip while everyone
else stood around complaining that it took WAY too long to fix the
Worst of all, the system had to stay hot 24 hours a day for immediate
use so scheduled maintenance was between 3:00 AM, and 6:00 AM. Of
course, Vital Industries was out of business soon after they shipped all
their equipment, and the only support was a former tech who managed to
grab the remaining boards and parts. That meant you had to fix it
yourself, unless you could afford not to do any production work till he
could get there a few weeks, or months after you called for support.
Michael A. Terrell
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