"My guess would be cost. Those headers back then were somewhat expensive due to the heavy (30) gold plating."
Wow. I never even considered that a header could be more costly than a 74LSXXX chip - doesn't make sense. But then again, I wasn't in the field back in that day. On Thu, Oct 1, 2015 at 10:48 PM, Tothwolf <tothw...@concentric.net> wrote: > On Thu, 1 Oct 2015, drlegendre . wrote: > > Also, I'm curious about the 50-pin headers.. why were they never >> installed? All of the other work was done, all the expensive parts (chips) >> are in-place - so why not a couple of cheap headers? Yes, a few resistor >> SIPs are gone, as is one chip missing, but still, you get the point. >> > > My guess would be cost. Those headers back then were somewhat expensive > due to the heavy (30) gold plating. > > I found out today that as of August 3M has discontinued their 3000 series > gray box headers and the last time buy on them was October 1st. They are > replacing them with the D3000 series made with black fiberglass reinforced > nylon instead of the gray nylon they've always used. (3000 series datasheet > attached) > > The part numbers for the 50-pin headers without eject levers for 1/16" > thick pc board would be 3433-5002. Mouser shows some stock, however their > system may or may not be correct and they might try to substitute the newer > D3000 series. > http://www.mouser.com/ProductDetail/3M/3433-5002/?qs=%2fha2pyFadugF4%2fyP%252bp8%252b57ygnI%2fCWx880e6iwa7L1bU7rpqbpN%252bwEQ%3d%3d > > I also spotted some 3433-5402 on eBay at a reasonable price that might > work, however those use a roll pin to attach the eject levers, so they are > much harder to remove than the ones that used snap-in eject levers. > http://www.ebay.com/itm/3M-3433-Locking-Ejector-Header-50-pin-right-angle-gold-plated-0-1-tails-1-x-1-/201386884555 > > Also, don't forget about C2. It and C1 were probably a matched set for the > crystal.
