I _know_ there are problems on the TU58. It should detect the BOT and EOT markers and not let the tape run off the spool. It should never produce the waveform I am seeing at the output of the read comparator. No matter what else works and doesn't work that is a fault I have to trace and fix. So I might as well fix that first rather than spending time setting up an emulator that I am not going to use in the end anyway and which will not help with the problem I am seeing. I've not had a chance to do much more on it today, but I have been reading the schematics time and again. Looks like the tape speed doesn't matter too much at least for reading, so even if my new rollers are not quite the right size t should work. What I haven't analysed yet is how the read comparator (labelled 'peak det' on the schematic) behaves if the input signal is very low amplitude. It may do odd things, and of course poor tape (or heads) would cause this, Time to investigate that further I think. -tony