TU58 problems

[tony duell]

> 
> Yeah, but if the emulator doesn't work,
> then you have another important clue.

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