Use REPLY rather than QUICK REPLY and it has an attachment facility, so you can post your sketch, files as an attachment.
I wish you would not encourage people to use attachments.
What affects me is that many of my computers cannot access the attachments due to the (apparently deliberate) way the forum software now obfuscates them (since the so-called “update” ).
And as it affects most people, ".pdf"s as attachments require a separate viewer, and ".ino"s require you to start up the IDE just to view them.
If images are lodged somewhere reputable (including previously on the Arduino.cc server), they can be linked into the text so they are immediately visible, and code posted in the correct tags is immediately usable.
74LS chips cannot really tolerate 5V on the inputs since even a small amount of rail noise will take them over the abs max or 5.5V.
No that would take 0.5V noise on the rail and that is not small is it? Never ever had any problems with connecting LS TTL to 5V, have you?
Whether the noise exceeded the “Absolute Maximum” rating is neither probably nor particularly significant. I fancy LS logic did include parasitic diodes which would clip this. I thought there was some other reason related to parasitics whereby actually tying to the Vcc rail resulted in a leakage current.
But the point is - the series is obsolete. If you have a heap of them lying around, maybe you would use them for a lurk, but the performance - notably quiescent current and speed - of CMOS is so much superior that you should never use them in a new design.
Some time back (it was!) I made a point of replacing the 7490s and such in our KYOKUTO FM144-10SXRII with LS chips - that radio has a bad reputation for unreliability and the heat build-up in the synthesiser section (as well as dodgy soldering apparently) was a clear contributor, so it was completely worthwhile to do all the de-soldering and replacement. It subsequently would make yet again more sense to replace it with HCMOS which I intend to do with another one that I came across. (Easier to operate than current models with lots of buttons and menus!) The later model had a chip with a Ni-Cd battery backup which needed to be replaced with a supercap. Were I to work on it now, I would of course replace the whole microcontroller with an ATMega328 using its EEPROM instead.