It looks like an 8881 is bad on the STATUS module.
Pins 5 and 6 are inputs, and pin 4 is the output of a NAND gate on the 8881. That sure looks like a bad part to me.
I’ve ordered a few spare Signetics N8881’s off of eBay, but… I have to admit, I’m really down and disheartened about the project tonight. I didn’t get more than an hour of debugging in tonight before I found this chip, and now I’ll be high and dry for another week until my chips come in. And what will I find next?
I really think this might be a lost cause. I hate to think about giving up after all the time and money I’ve poured into this so far. There are other projects I’d like to be working on, but I’ve had this PDP-11/35 occupying my entire workbench for a month now and I don’t feel like I’ve actually accomplished very much.
Well, maybe the feeling will pass. I’ll give it one more go. If I continue to find as many dead parts after getting past the 8881, I’ll reconsider whether it’s worth it to continue.