New pcb design for S-100 prototype board available
ragooman at comcast.net
Mon Jun 4 20:01:18 CDT 2007
Here's the specs I used from my Imsai 8080 backplane.
22slot , 8.5" x 17", 0.062"(1/16") thickness, 2 layer pcb, 2oz
copper(approx), plated thru holes, green solder mask top and bottom,
white silkscreen top, Hot Air Solder Level, 15day lead time.
I currently use a place called General Circuits Co.Ltd(China),
www.pcbcart.com. They've been providing a good quality service.
Imagineering is rather expensive if you ask me as most of them places
can be. For quick prototype, I also use Barebonespcb.com
The Imsai backplane is supported by a grid of standoff's at every other
slot position along both edges on the steel chassis. This is how it
retains it's strength when inserting many cards into the system. They
didn't need to make it any thicker. The only time I had thicker
backplane pcbs is for an industrial system, CPCI or VME systems, --which
this isn't-- then it's wise to make a 1/8" or 3/16" backplane. At my
last job,Lucent, our telecom backplanes were 1/2" thick. This is usually
the result of a 8,10,12 layer or more pcb. It also offers a system which
can withstand the rigors of an unpredictable environment. The Imsai,
Altair, and the like are just home systems.
The copper thickness is estimated but it has to be more than the
standard 1oz since this has a high current capacity.
I can recheck the cost projections for a thicker copper layer just in case.
All the sockets have gold plated contacts and are very good quality.
Good thing you mentioned the sockets. I was using a supplier which has a
dwindling supply(JDR)--checked it recently-- I hate when that happens.
They don't even have enough left over to make one backplane --uuggh--
and can't even bother to resupply. I had to source another supplier I
use for other stuff (Sullins Electronics). They have plenty but they
cost alittle more. To make it still reasonable, the batch order would
have to be 25 pieces at least and then the connectors would be down to
$15each.(I should double check the shipping again). The problem with
dealing directly with the vendors is that the prices they quote can
mysteriously fluctuate depending on the lifespan of a gnat
circumnavigating a buffalo's butt.
So a kit price would be way more expensive for a 22slot backplane
But you can always buy a few connectors at a clip and worry about
filling the backplane later.
Hey do I get a commission, now that I gave you some more suppliers :)
[ beauty is in the eye of the beer holder ]
[ http://ragooman.home.comcast.net/ ]
Grant Stockly wrote:
> Where do you get S-100 connectors for $5 or huge 1/8" PCBs for $35? I
> use Imagineering for PCBs and I can't get $35 a piece for 1/8 FR4
> 11x13" (being conservative) unless I order 50 with a 3 week lead time.
> I buy the same edge card connectors that MITS bought, minus one part
> number digit because I am buying non gold plated pins. The contacts
> are gold plated. If I buy 10 from DigiKey they are $14-$15. If I buy
> direct from the company they are $17-$20. : )
> I've heard horror stories from Todd Fisher about cheap sockets...
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