Actually, the only sources from whom one could, back when, rely on getting
out-of-spec parts were Poly-Pak and Radio Shack. At one time, one of my clients
was particularly pressed into buying 5-volt and 12-volt 3-terminal regulators
from RS because lead times were long and they needed to get boards and cabinetry
assembled in time for the holidays, so they bought regulators, some 1200 of them
from RS which wasn't an easy thing to do. Ultimately we established that, of
those 1200 regulators, not a one was in spec as far as the voltage it produced.
Some were out under light load, as for one drive, and some were out under heavy
load, as for a HDD. What we concluded from this was that RS had bought parts
that had already been rejected at either outgoing or incoming inspection, and
they were shipping those, either as parts or as parts of assemblies. Otherwise,
at least SOME of the parts were probably going to be within spec.
Recent experience supports this notion, as a kid up the street came to me with a
voltage regulator + pass transistor circuit he'd built, and correctly from what
I could see, for a project of his, but he'd used a regulator from RS, and it was
just not within spec. Fortunately, you can easily enough get parts that are in
spec just so you don't go to RS.
Dick
----- Original Message -----
From: "ajp166" <ajp166_at_bellatlantic.net>
To: <classiccmp_at_classiccmp.org>
Sent: Friday, November 02, 2001 8:43 PM
Subject: Re: CPU design at the gate level
> From: Ben Franchuk <bfranchuk_at_jetnet.ab.ca>
> >74x00's are still common - I still can get that at Radio-shack for $2.00
> >in a bubble
> >package here in Canada. It is rare chips ALU's, carry look aheads, 16x4
> >memory
> >that you can't find. The $.10 surplus TTL days are long gone. Ben
> >Franchuk.
>
>
>
> Good thing too as most of the surplus parts were off spec... I was burned
> a few times back when.
>
> At least three vendors have most of the TTL line, JDR being one.
>
> I might add that in '73 I did a TTL design, finding many of the chips
> that
> were in the books was a task as many were unobtainium.
>
> Allison
>
>
>
Received on Sat Nov 03 2001 - 11:56:40 GMT