2 Nov
2001
2 Nov
'01
1:43 p.m.
From: Ben Franchuk <bfranchuk(a)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
3 Nov
3 Nov
3:56 a.m.
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(a)bellatlantic.net>
To: <classiccmp(a)classiccmp.org>
Sent: Friday, November 02, 2001 8:43 PM
Subject: Re: CPU design at the gate level
From: Ben Franchuk <bfranchuk(a)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
4:44 a.m.
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5:53 a.m.
Is there an RS outlet that differs from the "corner Radio Shack" store in the
UK?
It happens that there's a "RadioShack.com" store, coincidentally here in
Denver,
and it seems to operate quite differently from the "corner Radio Shack."
They sell parts that seem to work properly, aren't blister-packed, and they
seem, most of the time, to have matching connector halves, pins and receptacles,
as well as the tools and materials needed to use them. It's really quite a
shop, though severely tainted by not only the Radio Shack name, but the product
lines as well. Whenever you need a PIC component, though, you can just go in
and hand them the money for it, as they've got 'em for the most part. They also
do an internet business and ship their parts, which means you, Tony, can order
from them, I do believe.
Their search engine leaves a little to be desired, however, so be prepared to
spend a little time with it until you find the "tricks" needed to get it to go
past the usual Radio Shack problem that the search engine doesn't know that you
might be able to use a 74F381 when you're searching for a 74AS381. You get the
picture ...
Dick
----- Original Message -----
From: "Tony Duell" <ard(a)p850ug1.demon.co.uk>
To: <classiccmp(a)classiccmp.org>
Sent: Saturday, November 03, 2001 11:44 AM
Subject: Re: CPU design at the gate level
Good thing too
as most of the surplus parts were off spec... I was burned
a few times back when.
THere used to be a company in the UK who bought up rejected ICs., tested
them, and sold them at seemingly low prices to hobbyists. There were only
2 problems
1) They would sell things like '7400, 75% good'. Meaning one defective
gate in the package. They didn't tell you which one. And the 'good' gates
tended to fail pretty quickly as well.
2) Their tester was based on telephone relays, uniselectors, and so on.
It ran at 1Hz, and that's being generous. Many of their 'tested, 100%
good' ICs failed at more sensible speeds.
I had a lot of problems with their devices. When I started buying
full-price TTL from RS components, etc, then I started having circuits
that worked first time...
-tony
6:13 a.m.
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