morphed to TTL part number history, was: IBM PLAYING CARDS

Chuck Guzis cclist at sydex.com
Sun Dec 18 16:12:03 CST 2005


I was talking with a fellow who worked for a local pipe organ builder (now
retired) about their needs for logic in the adjustable combination actions
of their instruments.   For non-organists, this basically is the mechanism
that allows a player to set combination of stops so that they are actuated
by depressing a button or a toe stud.  Basically a memory with a bit of
control logic driving some actuators connected to the drawknobs.

Given that we still have instruments around that were built in the 13th
century, I asked the guy what they did about making sure that there was a
100-200 year supply of replacement ICs.  IIRC, they used mostly 74LS TTL
and some CMOS and a bunch of power Darlingtons,etc. (a bit more about that
later).  He replied that they make up a care kit with 2 of everything and
place it safely away inside the console.   I opined that this hardly seemed
like enough.   He said that the function was simple enough that the kit was
mostly to get one past minor repairs; they expected that periodic redesigns
would be routlinely undertaken with the appropriate modern logic.   

BTW, the power components are mostly for visual effect.  He said that if a
tracker action instrument (which is what they made) was being installed,
organists demanded drawknobs that moved and not simple buttons, which would
be far easier to accomodate.  Go figure.

A couple of years ago, I was reading about the lock controls on the Panama
Canal and, at least until a few years ago,  they're still original
equipment installed in the 1910's, all that nice brass and mahogany stuff.
I read that a microprocessor-based system is slated to replace the old
circuitry; anyone want to guess if it'll still be intact 90 years after
installation?

Cheers,
Chuck






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