While working on the OPL-2 project, I had some trouble with my prototyping plug block. It's a wishboard, and I discovered, eventually that the two power rails are actually split in two. I wasn't getting any power to the chip because I was powering one end of the rails, but the chip was connected to the other ends, with a split in between.
No problem, sorted it out, everything works great.
But then I thought to myself, I'm sure I didn't do that when I built my digisnap.
I went and checked. It's built on exactly the same model wishboard, and it's true, I didn't connect the two halves of the power rails. It's been working perfectly for me for the past two years, despite the fact that the tri-state flip-flops which act as latches have NO POWER.