andrew wrote:

Whilst clearing out the loft at my mother's old house I have come across
some records. These were made in America in 1942 by her brother who was
training as RAF bomber crew. He died shortly after.

I think they are directly scribed into the plastic which is in poor nick,
possibly some mould growth. The discs are "Zenith Universal Recorder" and
probably done in some sort of booth.

I shall try and record them directly to wav files but before I attempt that
what precautions need I take? I have a problem in that my record deck only
has 33 and 45 rpm. Was mono 78 simply an amplitude modulation by depth of
the needle?

These are fragile disks, playing them can cause damage so you need to be
fairly sure that you have things set up properly before you start. As
others have said, the stylus needs to be specifically designed for 78s.
Don't try using the 33/45 rpm stylus because it will go to the bottom of
the groove and cause damage or scrape up the muck.

Those Ion turntables are absolute rubbish, a waste of money in almost
very respect. If you could get hold of a 78 turntable + cartridge and
stylus with a pre-amp and feed that into the line input on your Mac you
would do much better. OTOH if you were familiar with audio equipment I
guess you would have worked this out for yourself.

A new 78rpm cartridge and stylus will cost about £150. A decent
turntable could be as low as £40 with tonearm, if you're lucky you might
get a cartridge with it.