tracked it to a dead 1820-0732 on the option board. what is an 1820-0732? since i don't have a manual for the k20 and can't find the pin outs for the IC on the interweb.....who the fuck knows what it really is?
I really hate this, when this happens. I did a search in some HP cross references and found this:
![](https://i.imgur.com/ASz0Y7c.jpg)
The damn thing is sitting on your bench, evil grinning at you but the corresponding place in the list is empty.
![Confused :-//](https://www.eevblog.com/forum/Smileys/default/confused0024.gif)
Edit:
added the SN74190N datasheet from TI
The only explanation I have is: probably your IC is a SN74190N with the HP no. 1820-0734, so, some kind of typo in the list.
Edit 2:
Should have checked your schematic more carefully
![Face Palm :palm:](https://www.eevblog.com/forum/Smileys/default/facepalm.gif)
74190 doesn't fit. Probably HP has used a 74190 with some additional logic around, similar the way you did.
![Banging Head |O](https://www.eevblog.com/forum/Smileys/default/bangheadonwall.gif)