I'd like to verify that 74F##(#) family can replace the 74##(#) chips
which are getting rather expensive or of unknown (?) quality if one is
second sourcing them from folks like Unicorn, or eBay (shudder).
I am well aware the 74LS has may replacements including the 74ALS,
74HCT, and others, but they only fan-out to 10 LS gates or 1 original
gates.
I have older games that need reliable 74## and won't work reliably with
the lower fan-out stuff.
I have a Fairchild FAST DATA BOOK, but it doesn't actually say anywhere
I've read so far about how compatible it is with the original TTL
fan-outs. They do say that the F family are more susceptible to static
than 74S or 74LS so perhaps I will look at 74S in place of the originals
if they have a similar fan-out.
Suggestions welcome!
John :-#)#
I'd like to verify that 74F##(#) family can replace the 74##(#) chips
which are getting rather expensive or of unknown (?) quality if one is
second sourcing them from folks like Unicorn, or eBay (shudder).
I am well aware the 74LS has may replacements including the 74ALS,
74HCT, and others, but they only fan-out to 10 LS gates or 1 original
gates.
I have older games that need reliable 74## and won't work reliably with
the lower fan-out stuff.
I have a Fairchild FAST DATA BOOK, but it doesn't actually say anywhere
I've read so far about how compatible it is with the original TTL
fan-outs. They do say that the F family are more susceptible to static
than 74S or 74LS so perhaps I will look at 74S in place of the originals
if they have a similar fan-out.
Suggestions welcome!
John :-#)#
On Thu, 19 Oct 2023 13:49:12 -0700, John Robertson <jrr@flippers.com>
wrote:
I'd like to verify that 74F##(#) family can replace the 74##(#) chips
which are getting rather expensive or of unknown (?) quality if one is >>second sourcing them from folks like Unicorn, or eBay (shudder).
I am well aware the 74LS has may replacements including the 74ALS,
74HCT, and others, but they only fan-out to 10 LS gates or 1 original >>gates.
74HC or 74HCT should drive many old 74xx parts.
7400s only sourced about 1 mA at their inputs, and LS was 0.4 mA max.
A 74HC or HCT should easily drive five 74xx and scores of 74LS gates.
The hc/hct parts will be faster than the old TTLs, which could be a
problem with old hairball logic.
I have older games that need reliable 74## and won't work reliably with
the lower fan-out stuff.
I have a Fairchild FAST DATA BOOK, but it doesn't actually say anywhere >>I've read so far about how compatible it is with the original TTL
fan-outs. They do say that the F family are more susceptible to static
than 74S or 74LS so perhaps I will look at 74S in place of the originals
if they have a similar fan-out.
Suggestions welcome!
John :-#)#
I'd like to verify that 74F##(#) family can replace the 74##(#) chips which are
getting rather expensive or of unknown (?) quality if one is second sourcing them from folks like Unicorn, or eBay (shudder).
I am well aware the 74LS has may replacements including the 74ALS, 74HCT, and others, but they only fan-out to 10 LS gates or 1 original gates.
I have older games that need reliable 74## and won't work reliably with the lower fan-out stuff.
I have a Fairchild FAST DATA BOOK, but it doesn't actually say anywhere I've read so far about how compatible it is with the original TTL fan-outs. They do
say that the F family are more susceptible to static than 74S or 74LS so perhaps I will look at 74S in place of the originals if they have a similar fan-out.
Suggestions welcome!
I'd like to verify that 74F##(#) family can replace the 74##(#) chips
which are getting rather expensive or of unknown (?) quality if one is
second sourcing them from folks like Unicorn, or eBay (shudder).
I am well aware the 74LS has may replacements including the 74ALS,
74HCT, and others, but they only fan-out to 10 LS gates or 1 original
gates.
I have older games that need reliable 74## and won't work reliably with
the lower fan-out stuff.
I have a Fairchild FAST DATA BOOK, but it doesn't actually say anywhere
I've read so far about how compatible it is with the original TTL
fan-outs. They do say that the F family are more susceptible to static
than 74S or 74LS so perhaps I will look at 74S in place of the originals
if they have a similar fan-out.
Suggestions welcome!
John :-#)#
On 20/10/2023 7:49 am, John Robertson wrote:
I'd like to verify that 74F##(#) family can replace the 74##(#) chips
which are getting rather expensive or of unknown (?) quality if one is second sourcing them from folks like Unicorn, or eBay (shudder).
I am well aware the 74LS has may replacements including the 74ALS,
74HCT, and others, but they only fan-out to 10 LS gates or 1 original gates.
I have older games that need reliable 74## and won't work reliably with
the lower fan-out stuff.
I have a Fairchild FAST DATA BOOK, but it doesn't actually say anywhere I've read so far about how compatible it is with the original TTL
fan-outs. They do say that the F family are more susceptible to static
than 74S or 74LS so perhaps I will look at 74S in place of the originals
if they have a similar fan-out.
Suggestions welcome!
John :-#)#You should post your specific list of wanted parts here, or on the
EEVBLOG forum.
I have many 74xx parts (and 93xx too) (NOS and/or working used) that I
will probably never use in a new design, and almost none of the things I repair require them either.
I'd like to verify that 74F##(#) family can replace the 74##(#) chips
which are getting rather expensive or of unknown (?) quality if one is second sourcing them from folks like Unicorn, or eBay (shudder).
I am well aware the 74LS has may replacements including the 74ALS,
74HCT, and others, but they only fan-out to 10 LS gates or 1 original
gates.
I have older games that need reliable 74## and won't work reliably with
the lower fan-out stuff.
I have a Fairchild FAST DATA BOOK, but it doesn't actually say anywhere
I've read so far about how compatible it is with the original TTL
fan-outs. They do say that the F family are more susceptible to static
than 74S or 74LS so perhaps I will look at 74S in place of the originals
if they have a similar fan-out.
Suggestions welcome!
John :-#)#
--
(Please post followups or tech inquiries to the USENET newsgroup)
John's Jukes Ltd.
#7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3
(604)872-5757 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."
On Thu, 19 Oct 2023 16:37:39 -0700, john larkin <jl@650pot.com> wrote:
On Thu, 19 Oct 2023 13:49:12 -0700, John Robertson <jrr@flippers.com> >>wrote:
I'd like to verify that 74F##(#) family can replace the 74##(#) chips >>>which are getting rather expensive or of unknown (?) quality if one is >>>second sourcing them from folks like Unicorn, or eBay (shudder).
I am well aware the 74LS has may replacements including the 74ALS,
74HCT, and others, but they only fan-out to 10 LS gates or 1 original >>>gates.
74HC or 74HCT should drive many old 74xx parts.
7400s only sourced about 1 mA at their inputs, and LS was 0.4 mA max.
A 74HC or HCT should easily drive five 74xx and scores of 74LS gates.
The hc/hct parts will be faster than the old TTLs, which could be a
problem with old hairball logic.
Yes. I've had to interface new kit to very old kit. The answer was
Schmitt trigger for signals coming into new, and RC filters going into
old.
Joe Gwinn
I have older games that need reliable 74## and won't work reliably with >>>the lower fan-out stuff.
I have a Fairchild FAST DATA BOOK, but it doesn't actually say anywhere >>>I've read so far about how compatible it is with the original TTL >>>fan-outs. They do say that the F family are more susceptible to static >>>than 74S or 74LS so perhaps I will look at 74S in place of the
originals if they have a similar fan-out.
Suggestions welcome!
John :-#)#
On Thu, 19 Oct 2023 20:01:07 -0400, Joe Gwinn wrote:
On Thu, 19 Oct 2023 16:37:39 -0700, john larkin <j...@650pot.com> wrote:
On Thu, 19 Oct 2023 13:49:12 -0700, John Robertson <j...@flippers.com> >>wrote:
I'd like to verify that 74F##(#) family can replace the 74##(#) chips >>>which are getting rather expensive or of unknown (?) quality if one is >>>second sourcing them from folks like Unicorn, or eBay (shudder).
I am well aware the 74LS has may replacements including the 74ALS, >>>74HCT, and others, but they only fan-out to 10 LS gates or 1 original >>>gates.
74HC or 74HCT should drive many old 74xx parts.
7400s only sourced about 1 mA at their inputs, and LS was 0.4 mA max.
A 74HC or HCT should easily drive five 74xx and scores of 74LS gates.
The hc/hct parts will be faster than the old TTLs, which could be a >>problem with old hairball logic.
Yes. I've had to interface new kit to very old kit. The answer was
Schmitt trigger for signals coming into new, and RC filters going into old.
Joe Gwinn
I recall some instances of people switching existing TTL designs to HC,
and discovering that termination or better termination was required on
clock and data lines. The RC filter should prevent that problem.
I have a box of old IC's containing a bunch of 74xx parts in original Jim- Pak or Active Electronics packaging, mostly unopened, I could send the
74xx parts or the entire box for you to sort including various counters, shift registers, PLL's, more LS than plain TTL but contents largely unremembered, possibly old memory. The empty space is now more valuable
than the parts to me, and I would rather pay postage to someone who can
use them than throw them out.
Glen
I have older games that need reliable 74## and won't work reliably with >>>the lower fan-out stuff.
I have a Fairchild FAST DATA BOOK, but it doesn't actually say anywhere >>>I've read so far about how compatible it is with the original TTL >>>fan-outs. They do say that the F family are more susceptible to static >>>than 74S or 74LS so perhaps I will look at 74S in place of the >>>originals if they have a similar fan-out.
Suggestions welcome!
John :-#)#
On Thu, 19 Oct 2023 20:01:07 -0400, Joe Gwinn wrote:
On Thu, 19 Oct 2023 16:37:39 -0700, john larkin <jl@650pot.com> wrote:
On Thu, 19 Oct 2023 13:49:12 -0700, John Robertson <jrr@flippers.com> >>>wrote:
I'd like to verify that 74F##(#) family can replace the 74##(#) chips >>>>which are getting rather expensive or of unknown (?) quality if one is >>>>second sourcing them from folks like Unicorn, or eBay (shudder).
I am well aware the 74LS has may replacements including the 74ALS, >>>>74HCT, and others, but they only fan-out to 10 LS gates or 1 original >>>>gates.
74HC or 74HCT should drive many old 74xx parts.
7400s only sourced about 1 mA at their inputs, and LS was 0.4 mA max.
A 74HC or HCT should easily drive five 74xx and scores of 74LS gates.
The hc/hct parts will be faster than the old TTLs, which could be a >>>problem with old hairball logic.
Yes. I've had to interface new kit to very old kit. The answer was
Schmitt trigger for signals coming into new, and RC filters going into
old.
Joe Gwinn
I recall some instances of people switching existing TTL designs to HC,
and discovering that termination or better termination was required on
clock and data lines. The RC filter should prevent that problem.
I have a box of old IC's containing a bunch of 74xx parts in original Jim- >Pak or Active Electronics packaging, mostly unopened, I could send the
74xx parts or the entire box for you to sort including various counters, >shift registers, PLL's, more LS than plain TTL but contents largely >unremembered, possibly old memory. The empty space is now more valuable
than the parts to me, and I would rather pay postage to someone who can
use them than throw them out.
On 20/10/2023 7:49 am, John Robertson wrote:
I'd like to verify that 74F##(#) family can replace the 74##(#) chips
which are getting rather expensive or of unknown (?) quality if one is
second sourcing them from folks like Unicorn, or eBay (shudder).
I am well aware the 74LS has may replacements including the 74ALS,
74HCT, and others, but they only fan-out to 10 LS gates or 1 original
gates.
I have older games that need reliable 74## and won't work reliably
with the lower fan-out stuff.
I have a Fairchild FAST DATA BOOK, but it doesn't actually say
anywhere I've read so far about how compatible it is with the original
TTL fan-outs. They do say that the F family are more susceptible to
static than 74S or 74LS so perhaps I will look at 74S in place of the
originals if they have a similar fan-out.
Suggestions welcome!
John :-#)#
You should post your specific list of wanted parts here, or on the
EEVBLOG forum.
I have many 74xx parts (and 93xx too) (NOS and/or working used) that I
will probably never use in a new design, and almost none of the things I repair require them either.
On Thu, 19 Oct 2023 13:49:12 -0700, John Robertson <jrr@flippers.com>
wrote:
I'd like to verify that 74F##(#) family can replace the 74##(#) chips
which are getting rather expensive or of unknown (?) quality if one is
second sourcing them from folks like Unicorn, or eBay (shudder).
I am well aware the 74LS has may replacements including the 74ALS,
74HCT, and others, but they only fan-out to 10 LS gates or 1 original
gates.
I have older games that need reliable 74## and won't work reliably with
the lower fan-out stuff.
I have a Fairchild FAST DATA BOOK, but it doesn't actually say anywhere
I've read so far about how compatible it is with the original TTL
fan-outs. They do say that the F family are more susceptible to static
than 74S or 74LS so perhaps I will look at 74S in place of the originals
if they have a similar fan-out.
Suggestions welcome!
John :-#)#
How about 74HC parts ?
That's pretty much what I have been using for the last several years
boB
On Thu, 19 Oct 2023 20:01:07 -0400, Joe Gwinn wrote:
On Thu, 19 Oct 2023 16:37:39 -0700, john larkin <jl@650pot.com> wrote:
On Thu, 19 Oct 2023 13:49:12 -0700, John Robertson <jrr@flippers.com>
wrote:
I'd like to verify that 74F##(#) family can replace the 74##(#) chips
which are getting rather expensive or of unknown (?) quality if one is >>>> second sourcing them from folks like Unicorn, or eBay (shudder).
I am well aware the 74LS has may replacements including the 74ALS,
74HCT, and others, but they only fan-out to 10 LS gates or 1 original
gates.
74HC or 74HCT should drive many old 74xx parts.
7400s only sourced about 1 mA at their inputs, and LS was 0.4 mA max.
A 74HC or HCT should easily drive five 74xx and scores of 74LS gates.
The hc/hct parts will be faster than the old TTLs, which could be a
problem with old hairball logic.
Yes. I've had to interface new kit to very old kit. The answer was
Schmitt trigger for signals coming into new, and RC filters going into
old.
Joe Gwinn
I recall some instances of people switching existing TTL designs to HC,
and discovering that termination or better termination was required on
clock and data lines. The RC filter should prevent that problem.
I have a box of old IC's containing a bunch of 74xx parts in original Jim- Pak or Active Electronics packaging, mostly unopened, I could send the
74xx parts or the entire box for you to sort including various counters, shift registers, PLL's, more LS than plain TTL but contents largely unremembered, possibly old memory. The empty space is now more valuable
than the parts to me, and I would rather pay postage to someone who can
use them than throw them out.
Glen
On 2023/10/20 7:47 a.m., Fred Bloggs wrote:
On Thursday, October 19, 2023 at 4:49:40 PM UTC-4, John Robertson wrote:
I'd like to verify that 74F##(#) family can replace the 74##(#) chips
which are getting rather expensive or of unknown (?) quality if one is
second sourcing them from folks like Unicorn, or eBay (shudder).
I am well aware the 74LS has may replacements including the 74ALS,
74HCT, and others, but they only fan-out to 10 LS gates or 1 original
gates.
I have older games that need reliable 74## and won't work reliably with >> the lower fan-out stuff.
I have a Fairchild FAST DATA BOOK, but it doesn't actually say anywhere >> I've read so far about how compatible it is with the original TTL
fan-outs. They do say that the F family are more susceptible to static
than 74S or 74LS so perhaps I will look at 74S in place of the originals >> if they have a similar fan-out.
FAST logic is superior in all respects, is totally compatible with 74 TTL, uses way less power, and the Tpd is about 1/5 that of TTL.
It's overkill iow.
The HC drives TTL, but the question is does TTL drive it. Technically, no it doesn't, and that's what HCT is about.
If you can eyeball the circuit enough to determine the specific fan-ins/outs then LS should be the cheapest option, and the least problem because of identical I/O performance VIL VIH VOL VOH, mins/maxs etc.
Logic families were all designed to be compatible with itself. They will also, somewhere in the data book, define a unit fan H/L in uA or mA. That tells you all you need to know to translate loading/drive mixed with another family.Thanks Fred, I figured 74F should work - interesting that another poster mentioned is is essentially 74AS which widens the available sources as well.
As you say, while HC is not compatible with TTL, and HCT is 'usually',
I'm looking for drop-in without having to redesign anything - these are
for repairs, not new designs. Repairs need to be done on a timely
fashion or customers get annoyed with really high bills for time spent
on upgrades so the newer parts will work.
I do design some new simple boards and try to use modern TTL that is not being discontinued or there is a huge supply of the parts for future service.
John :-#)#
--
(Please post followups or tech inquiries to the USENET newsgroup)
John's Jukes Ltd.
#7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3
(604)872-5757 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."
On 2023/10/19 2:37 p.m., boB wrote:
On Thu, 19 Oct 2023 13:49:12 -0700, John Robertson <jrr@flippers.com>
wrote:
I'd like to verify that 74F##(#) family can replace the 74##(#) chips
which are getting rather expensive or of unknown (?) quality if one is
second sourcing them from folks like Unicorn, or eBay (shudder).
I am well aware the 74LS has may replacements including the 74ALS,
74HCT, and others, but they only fan-out to 10 LS gates or 1 original
gates.
I have older games that need reliable 74## and won't work reliably with
the lower fan-out stuff.
I have a Fairchild FAST DATA BOOK, but it doesn't actually say anywhere
I've read so far about how compatible it is with the original TTL
fan-outs. They do say that the F family are more susceptible to static
than 74S or 74LS so perhaps I will look at 74S in place of the originals >>> if they have a similar fan-out.
Suggestions welcome!
John :-#)#
How about 74HC parts ?
Too many problems when interfacing HC with older TTL. Both HC and HCT
are essentially LS in fan-out and their output voltages don't work in a >number of circuits. I was servicing one game where the board designer >substituted HCT in place of the original LS and the HCT chips would not
drive the optos correctly. Took a while to track that down as I had
assumed the board redesign had been done correctly...
That's pretty much what I have been using for the last several years
boB
Sometimes they work, often they introduce new problems. And if one is
dealing with a component level board with several issues adding a new
problem to the mix isn't optimal.
John :-#(#
Hi Chris,
On 2023/10/20 5:31 a.m., Chris Jones wrote:
On 20/10/2023 7:49 am, John Robertson wrote:
I'd like to verify that 74F##(#) family can replace the 74##(#) chips
which are getting rather expensive or of unknown (?) quality if one
is second sourcing them from folks like Unicorn, or eBay (shudder).
I am well aware the 74LS has may replacements including the 74ALS,
74HCT, and others, but they only fan-out to 10 LS gates or 1 original
gates.
I have older games that need reliable 74## and won't work reliably
with the lower fan-out stuff.
I have a Fairchild FAST DATA BOOK, but it doesn't actually say
anywhere I've read so far about how compatible it is with the
original TTL fan-outs. They do say that the F family are more
susceptible to static than 74S or 74LS so perhaps I will look at 74S
in place of the originals if they have a similar fan-out.
Suggestions welcome!
John :-#)#
You should post your specific list of wanted parts here, or on the
EEVBLOG forum.
I use pretty service much the entire 74## family in my board repairs.
Fixing the very first arcade games (Nutting's Computer Space) to use TTL through to modern stuff - which has other supply issues of course.
I have many 74xx parts (and 93xx too) (NOS and/or working used) that I
will probably never use in a new design, and almost none of the things
I repair require them either.
If you are willing to ship them to me, I'd be happy to refund your
postage (parcel post) - my shop address is below.
On 2023/10/20 10:14 a.m., Fred Bloggs wrote:
On Friday, October 20, 2023 at 1:05:10 PM UTC-4, John Robertson wrote:
On 2023/10/20 7:47 a.m., Fred Bloggs wrote:
On Thursday, October 19, 2023 at 4:49:40 PM UTC-4, John Robertson wrote:Thanks Fred, I figured 74F should work - interesting that another poster >> mentioned is is essentially 74AS which widens the available sources as well.
I'd like to verify that 74F##(#) family can replace the 74##(#) chips >>>> which are getting rather expensive or of unknown (?) quality if one is >>>> second sourcing them from folks like Unicorn, or eBay (shudder).
I am well aware the 74LS has may replacements including the 74ALS,
74HCT, and others, but they only fan-out to 10 LS gates or 1 original >>>> gates.
I have older games that need reliable 74## and won't work reliably with >>>> the lower fan-out stuff.
I have a Fairchild FAST DATA BOOK, but it doesn't actually say anywhere >>>> I've read so far about how compatible it is with the original TTL
fan-outs. They do say that the F family are more susceptible to static >>>> than 74S or 74LS so perhaps I will look at 74S in place of the originals
if they have a similar fan-out.
FAST logic is superior in all respects, is totally compatible with 74 TTL, uses way less power, and the Tpd is about 1/5 that of TTL.
It's overkill iow.
The HC drives TTL, but the question is does TTL drive it. Technically, no it doesn't, and that's what HCT is about.
If you can eyeball the circuit enough to determine the specific fan-ins/outs then LS should be the cheapest option, and the least problem because of identical I/O performance VIL VIH VOL VOH, mins/maxs etc.
Logic families were all designed to be compatible with itself. They will also, somewhere in the data book, define a unit fan H/L in uA or mA. That tells you all you need to know to translate loading/drive mixed with another family.
FAST (Fairchild Advanced Schottky TTL)Dang, it says that right on the cover!
I need to RTFM obviously - COVER to cover...
On Friday, October 20, 2023 at 10:42:42?AM UTC-4, Glen Walpert wrote:
On Thu, 19 Oct 2023 20:01:07 -0400, Joe Gwinn wrote:
On Thu, 19 Oct 2023 16:37:39 -0700, john larkin <j...@650pot.com> wrote: >> >I recall some instances of people switching existing TTL designs to HC,
On Thu, 19 Oct 2023 13:49:12 -0700, John Robertson <j...@flippers.com>
wrote:
I'd like to verify that 74F##(#) family can replace the 74##(#) chips
which are getting rather expensive or of unknown (?) quality if one is
second sourcing them from folks like Unicorn, or eBay (shudder).
I am well aware the 74LS has may replacements including the 74ALS,
74HCT, and others, but they only fan-out to 10 LS gates or 1 original
gates.
74HC or 74HCT should drive many old 74xx parts.
7400s only sourced about 1 mA at their inputs, and LS was 0.4 mA max.
A 74HC or HCT should easily drive five 74xx and scores of 74LS gates.
The hc/hct parts will be faster than the old TTLs, which could be a
problem with old hairball logic.
Yes. I've had to interface new kit to very old kit. The answer was
Schmitt trigger for signals coming into new, and RC filters going into
old.
Joe Gwinn
and discovering that termination or better termination was required on
clock and data lines. The RC filter should prevent that problem.
That was the 3x faster output rise/fall time doing that.
I have a box of old IC's containing a bunch of 74xx parts in original Jim- >> Pak or Active Electronics packaging, mostly unopened, I could send the
74xx parts or the entire box for you to sort including various counters,
shift registers, PLL's, more LS than plain TTL but contents largely
unremembered, possibly old memory. The empty space is now more valuable
than the parts to me, and I would rather pay postage to someone who can
use them than throw them out.
Glen
I have older games that need reliable 74## and won't work reliably with >> >>>the lower fan-out stuff.
I have a Fairchild FAST DATA BOOK, but it doesn't actually say anywhere >> >>>I've read so far about how compatible it is with the original TTL
fan-outs. They do say that the F family are more susceptible to static
than 74S or 74LS so perhaps I will look at 74S in place of the
originals if they have a similar fan-out.
Suggestions welcome!
John :-#)#
On Fri, 20 Oct 2023 07:50:14 -0700 (PDT), Fred Bloggs <bloggs.fred...@gmail.com> wrote:
On Friday, October 20, 2023 at 10:42:42?AM UTC-4, Glen Walpert wrote:
On Thu, 19 Oct 2023 20:01:07 -0400, Joe Gwinn wrote:
On Thu, 19 Oct 2023 16:37:39 -0700, john larkin <j...@650pot.com> wrote:I recall some instances of people switching existing TTL designs to HC, >> and discovering that termination or better termination was required on
On Thu, 19 Oct 2023 13:49:12 -0700, John Robertson <j...@flippers.com> >> >>wrote:
I'd like to verify that 74F##(#) family can replace the 74##(#) chips >> >>>which are getting rather expensive or of unknown (?) quality if one is >> >>>second sourcing them from folks like Unicorn, or eBay (shudder).
I am well aware the 74LS has may replacements including the 74ALS,
74HCT, and others, but they only fan-out to 10 LS gates or 1 original >> >>>gates.
74HC or 74HCT should drive many old 74xx parts.
7400s only sourced about 1 mA at their inputs, and LS was 0.4 mA max. >> >>A 74HC or HCT should easily drive five 74xx and scores of 74LS gates. >> >>
The hc/hct parts will be faster than the old TTLs, which could be a
problem with old hairball logic.
Yes. I've had to interface new kit to very old kit. The answer was
Schmitt trigger for signals coming into new, and RC filters going into >> > old.
Joe Gwinn
clock and data lines. The RC filter should prevent that problem.
That was the 3x faster output rise/fall time doing that.
In the early days of AC logic, I was amazed to see well sub-nS edges
I have a box of old IC's containing a bunch of 74xx parts in original Jim-
Pak or Active Electronics packaging, mostly unopened, I could send the
74xx parts or the entire box for you to sort including various counters, >> shift registers, PLL's, more LS than plain TTL but contents largely
unremembered, possibly old memory. The empty space is now more valuable >> than the parts to me, and I would rather pay postage to someone who can >> use them than throw them out.
Glen
I have older games that need reliable 74## and won't work reliably with
the lower fan-out stuff.
I have a Fairchild FAST DATA BOOK, but it doesn't actually say anywhere
I've read so far about how compatible it is with the original TTL
fan-outs. They do say that the F family are more susceptible to static >> >>>than 74S or 74LS so perhaps I will look at 74S in place of the
originals if they have a similar fan-out.
Suggestions welcome!
John :-#)#
from cheap parts.
Some of the Tiny cmos parts are crazy fast.
https://www.dropbox.com/scl/fi/iugv8wzmh3ie9zzmv8vpi/NC7SV74_2.JPG?rlkey=tkdj4ire4e92wixk57omm8k2o&dl=0
On Fri, 20 Oct 2023 07:50:14 -0700 (PDT), Fred Bloggs <bloggs.fred...@gmail.com> wrote:
On Friday, October 20, 2023 at 10:42:42?AM UTC-4, Glen Walpert wrote:
On Thu, 19 Oct 2023 20:01:07 -0400, Joe Gwinn wrote:
On Thu, 19 Oct 2023 16:37:39 -0700, john larkin <j...@650pot.com> wrote:I recall some instances of people switching existing TTL designs to HC, >> and discovering that termination or better termination was required on
On Thu, 19 Oct 2023 13:49:12 -0700, John Robertson <j...@flippers.com> >> >>wrote:
I'd like to verify that 74F##(#) family can replace the 74##(#) chips >> >>>which are getting rather expensive or of unknown (?) quality if one is >> >>>second sourcing them from folks like Unicorn, or eBay (shudder).
I am well aware the 74LS has may replacements including the 74ALS,
74HCT, and others, but they only fan-out to 10 LS gates or 1 original >> >>>gates.
74HC or 74HCT should drive many old 74xx parts.
7400s only sourced about 1 mA at their inputs, and LS was 0.4 mA max. >> >>A 74HC or HCT should easily drive five 74xx and scores of 74LS gates. >> >>
The hc/hct parts will be faster than the old TTLs, which could be a
problem with old hairball logic.
Yes. I've had to interface new kit to very old kit. The answer was
Schmitt trigger for signals coming into new, and RC filters going into >> > old.
Joe Gwinn
clock and data lines. The RC filter should prevent that problem.
That was the 3x faster output rise/fall time doing that.
In the early days of AC logic, I was amazed to see well sub-nS edges
I have a box of old IC's containing a bunch of 74xx parts in original Jim-
Pak or Active Electronics packaging, mostly unopened, I could send the
74xx parts or the entire box for you to sort including various counters, >> shift registers, PLL's, more LS than plain TTL but contents largely
unremembered, possibly old memory. The empty space is now more valuable >> than the parts to me, and I would rather pay postage to someone who can >> use them than throw them out.
Glen
I have older games that need reliable 74## and won't work reliably with
the lower fan-out stuff.
I have a Fairchild FAST DATA BOOK, but it doesn't actually say anywhere
I've read so far about how compatible it is with the original TTL
fan-outs. They do say that the F family are more susceptible to static >> >>>than 74S or 74LS so perhaps I will look at 74S in place of the
originals if they have a similar fan-out.
Suggestions welcome!
John :-#)#
from cheap parts.
Some of the Tiny cmos parts are crazy fast.
https://www.dropbox.com/scl/fi/iugv8wzmh3ie9zzmv8vpi/NC7SV74_2.JPG?rlkey=tkdj4ire4e92wixk57omm8k2o&dl=0
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