The TD8E and TU56 DECtape on the PDP-8/E is now working, mostly.
This morning it failed diagnostics when they it to write and then read back the Data Register. It took me a few hours to find a 7474 flip-flop IC, E03 for the UTS signal, that had both the 0 and the 1 outputs high. This was sending extra CLK signals to the 8271 ICs that make up the Data Register and corrupting the data. We have found lots of bad 7474 ICs, so I replaced the chip but it didn't change anything. I then found that both the SET and PRESET signals on the 7474 were low making both the 0 and the 1 outputs high. Eventually I found that the WTM switch was in the ON position, and should not be for normal use. That was a dumb mistake.
Even after setting the WTM switch to the correct position, the TD8E still fails diags when it is waiting for a quad-line flag. I need to investigate that further.
I was able to use David Gesswein's resttd8e program to make a bootable OS/8 DECtape from an image on my laptop. There is something not quite right about the DECtape that I made because when I boot OS/8 from the DECtape it halts when I try to do a directory listing. Listing, reading, and writing the DECtape from OS/8 booted from Kyle Owen's serial disk emulator works fine. Maybe the OS/8 image on the DECtape doesn't match the hardware configuration that I have? I have several TU56 DECtape images, so I will try the others.
I still need to look for the possible AC clearing glitch when executing the SDLD instruction.