Re: Wall of RAM

On Thu, 26 Jan 2006 00:23:02 -0800, logjam wrote:

> I was soldering the 14th board on Tuesday. After a little over 600 LEDs I
> found that they were ALL in backwards!!!! : ( I don't have any spare
> boars. At least 300 of the LEDs will need to be desoldered (but I have a
> nice station so it shouldn't take too long). Its easier than it sounds
> since I spray painted the boards black. Once I "think" I have the board
> orientation right I was just blindly pushing them in. Soldering 10,000
> LEDs at 1000 a day tends to do that to you. ;)
>
> At this point I am VERY sick of the 20k LED project. So I decide to
> visually (lighting the LEDs) test the 13 completed boards of 990.
>
> I found one other board where I did 32 rows of 30 correctly and put one
> row of 30 in backwards.
>
> The other most common defect was soldering one pin and not soldering the
> other.
>
> I found that most of my brother's solder joints were cold, so I went ahead
> and reflowed about 3 boards of 990 just to be safe even before I did a
> test lighting.
>
> If I solder one board Thursday and one board Friday I will have 3 boards
> for Saturday. At peak efficiency it will take 12 hours of solid soldring
> to do 3 boards of 990. I have to get them done by the 28th to win that
> bet. ; )
>
> My next project is to make a set of PCBs for the Magic-1 TTL computer. I
> think that even better than an Altair driving the display would be a TTL
> computer. :)

OK, what's a "Magic-1"? Oh, wait a sec - google is our friend....
"Your search - "magic-1 ttl computer" - did not match any documents."

When I think "TTL Computer", I think DEC PDP-11, National IMP-16, and
Control Data Enhanced Normandale Controller/Tester. :-)

They all used 74181's. I also used to read the AMD AM2901 bit-slice
manuals and app notes, but I don't know if those things can even be
had in this century. )-;

(I'm sure the whole thing could be done in a CPLD, but what's the
fun in that? ;-) )

Good Luck!
Rich


.

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