Yep, those old plain 7400 series TTL ics are little juice-hogs! Changing that whole thing over to 74LS is a good idea. The plain old 7400 series TTL works ok, but it hogs a lot more current, and it's also much more susceptible to noise and transient spikes. 74LS series is a vast improvement!
But, you are correct in your observation that when changing from plain 74XX to 74LSXX, that particular attention must be paid to current availability. Swapping out those resistors sounds reasonable. > > >---- Original Message ---- >From: dave.do...@comcast.net >To: neonixie-l@googlegroups.com >Subject: RE: [neonixie-l] Re: Taylor Edge Nixie Clock Kit >Date: Thu, 30 Mar 2017 18:25:39 -0700 (PDT) > >>Sorry that it took me so long to get back about this clock problem. >We have >>the clock work perfectly now. I have to give my friend Mike all the >credit >>for figuring this out. It appears that the original clock design >schematic >>calls for 7400 series ICs but the BOM calls for 74LSXX. Mike has a >IC spec. >>book and after comparing the differences in the ICs we found that >the >>74LSXX have an output of 8ma and the 7400 series have an output of >16ma. We >>believe that the original design was for 7400 but in shopping for >them >>found that there are very few suppliers anymore. We think that this >is why >>they changed the BOM to 74LSXX. With the smaller output from the >74LSXX IC >>and the amount of resistance in that circuit the current was >marginal and >>not enough current to drive the other ICs correctly in the circuit. >We >>ended up removing R1 and R3 (360 ohm) and leaving everything else >the way >>it was. It works perfect now and all of the setting switches work >fine >>also. Thanks for all the feedback from everyone >> >>Dave >> >>On Tuesday, March 7, 2017 at 6:37:54 PM UTC-6, dave....@comcast.net >wrote: >>> >>> I'm hoping that someone out there can help me with a problem that >I am >>> having with a Taylor Edge clock kit that I built. After completing >the kit >>> and plugging it in it seemed to be working fine. Then I noticed >that the >>> 10s second display tube and the 10s minute display tube were not >counting >>> correctly. They would count from 2 to 3 to 4 to 5 but then it >would go back >>> to 3 then 4 then back to 2 and then start the sequence over again. >The 1s >>> second and 10s minute tubes would count fine. I asked a friend of >mine that >>> knows a lot more about this stuff than I do and he recommended >that I try >>> disconnecting resistors R13 and R15 (both 240 ohm) from the time >setting >>> circuit to see what would happen. This fixed the counting problem >but now I >>> cannot set the time. I can't believe that I am the only person >that has had >>> this problem and am hoping someone out there knows the answer. I >am >>> attaching the schematic. >>> >>> Thanks >>> Dave >>> >> >>-- >>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 neonixie-l+unsubscr...@googlegroups.com. >>To post to this group, send an email to neonixie-l@googlegroups.com. >>To view this discussion on the web, visit >https://groups.google.com/d/msgid/neonixie-l/51ff2297-8b93-4126-a14c- >6a31687c11a1%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 neonixie-l+unsubscr...@googlegroups.com. To post to this group, send an email to neonixie-l@googlegroups.com. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/380-220173531111822423%40all2easy.net. For more options, visit https://groups.google.com/d/optout.
