360 ohms is way too little resistance for *any* sort of TTL pullup resistor! That apparently got confused with the standard *pull down* resistor used to keep an unattended TTL input *low*. 360 ohms for a TTL pulldown is just right.
2.2k ohms is the standard value to use as a TTL pullup. That goes for regular old 7400 series TTL, as well as 74LS series. The old military practice was to always use 1k ohm as the standard TTL pullup resistor value. Note that even when using that 1k pullup resistance, that all we are asking of any TTL gate which is pulled up by this, is to be able to provide 5 milliamperes in order for for the output to go low. Even that value of 1k ohm would work ok with either plain 7400 or 74LS. 2.2k is much more like it, however. At that value, all we are asking is 2.3 mA, and that works fine. 360 ohms is just simply too close to being a piece of wire!! (This is all explained in great detail on page 12 of Don Lancaster's famous TTL Cookbook) ---- Original Message ---- From: [email protected] To: [email protected] Subject: [neonixie-l] Re: Taylor Edge Nixie Clock Kit Date: Thu, 30 Mar 2017 19:38:26 -0700 (PDT) > > > >I'm a little late to the party, and the discussion between old 74xx >versus >74LSxx caught my attention. In most cases, I'd favor the newer 74LS >over >the original 74xx. But the resistor values (360 ohm) paint you into >using >the older series, because 5V / 360ohms gives you 13.9mA. The value >seems to >have been chosen because of the set switch resistor values.Of course >as the >OP mentioned, removing all the 360 ohm resistors lets the unit >operate >properly. The set switches may work adequately, too. > ><https://lh3.googleusercontent.com/-k_4j6X4xaEs/WN3AZVxQbgI/AAAAAAAAY >lU/Wcu3xmkZidsfPKYgHCTU5VlWEi_nSXiWACLcB/s1600/Taylor_Clock.jpg> > >Personally, I prefer 4000 series CMOS, for this kind of thing. > > >Good to see that the OP, and his buddy, figured it out. > >-- >You received this message because you are subscribed to the Google >Groups "neonixie-l" group. >To unsubscribe from this group and stop receiving emails from it, >send an email to [email protected]. >To post to this group, send an email to [email protected]. >To view this discussion on the web, visit >https://groups.google.com/d/msgid/neonixie-l/6d9e738a-b183-4284-846e- >d1e2091fefa1%40googlegroups.com. >For more options, visit https://groups.google.com/d/optout. $4.95/mo. National Dialup, Anti-Spam, Anti-Virus, 5mb personal web space. 5x faster dialup for only $9.95/mo. No contracts, No fees, No Kidding! See http://www.All2Easy.net for more details! -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send an email to [email protected]. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/380-220173531114249955%40all2easy.net. For more options, visit https://groups.google.com/d/optout.
