Re: 1540/2031 schematic error?

Thinking twice about this, it *might* be just irrelevant since that
counter always counts up to 7, so how the MSB is initialized doesn't
change anything (since the MSB output or carry output aren't used). I
am still curious however if someone can check on an actual PCB if that
pin 9 was just left floating or connected anywhere else. I still don't
understand why they didn't use just another LS193 (there're already a
few used on these drives so it would make sense for inventory
reduction) but opted instead for an LS191 that does something
apparently perfectly possible with the LS193. The 4040 uses an LS190
in the corresponding place, but that's a bit different because of the
external hardware GCR decoder.
Any ideas are welcome, if my considerations make sense :)
Frank

On Tue, Feb 20, 2024 at 10:12 AM Francesco Messineo
<francesco.messineo_at_gmail.com> wrote:
>
> Hi all,
> I think there's an error on both the 1540 (1541 long board) and the
> 2031 (both HP and LP).
> Input pin 9 of 74LS191 U5L (on the HP schematic, 1540/LP is a
> different position) isn't shown.
> I *think* it should be grounded but I don't have any long board or
> 2031 to confirm. Can anyone check on the real hardware?
> I was curious to understand why they used this LS191 instead of the
> LS193 (that's already present in different circuit parts) and  pin 9
> could be why, if it's not grounded.
> Any help is welcome.
> Frank IZ8DWF