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."
Substitutes for the 7400 family....
Started by ●October 19, 2023
Reply by ●October 19, 20232023-10-19
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
Reply by ●October 19, 20232023-10-19
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 :-#)#
Reply by ●October 19, 20232023-10-19
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 :-#)#
Reply by ●October 19, 20232023-10-19
On 10/19/2023 1:49 PM, 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'd be more worried that moving to faster logic will reveal hazzards in the (ahem) "designs". A lot of that logic was really more of "Oh, it SEEMS to work" than "Yes, it WILL work". E.g., gating clocks, etc. You may find some hold times violated or "glitches" introduced as some signals propagate through the logic faster than others/expected. A static analysis should be sufficient to verify the worst case conditions of signals propagating through whatever combination of devices in a signal path will give you the desired signals and timings.> 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.F is a marketing ploy for what everyone else calls AS. (I recall a disti equating it to "Fairchild And Schweber Together") So, it's got much shorter propagation delays and higher fanouts. Watch *total* power consumption for designs that used a lot of parts.> Suggestions welcome!HCT is often a good choice. Again, recheck the designs as you may find intermittent behavior (e.g., if a glitch gets through the logic and triggers a latch at the wrong time)
Reply by ●October 20, 20232023-10-20
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.
Reply by ●October 20, 20232023-10-20
On Friday, 20 October 2023 at 13:31:29 UTC+1, 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 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.You might like to look at 74HCS devices. There are not a lot of them, but they do all have Schmitt trigger inputs. If you need DIL packages that might be a problem unless you make adapter boards. John
Reply by ●October 20, 20232023-10-20
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>>>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 :-#)#
Reply by ●October 20, 20232023-10-20
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.> > 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."
Reply by ●October 20, 20232023-10-20
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: > > > >>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.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 :-#)#
