Ampex HS100

Back in that time long ago when television was worth watching and half-ton Quadruplex video
recorders lurked in the basement of the BBC Television Centre, there were, actually no means of
doing slow motion or still frames. This is because the very nature of the television system is based
upon a continuous and highly stable analogue signal flow. But the Quadruplex recorder 'chopped'
this signal into a number of segments, only re-constituting them as a continuous video signal on
playback.

However, in 1968 by using the concept of a 'stuck gramophone needle' Ampex built a magnetic
video disk recorder that did provide broadcast quality slow motion and still images to keep the
sports people happy. As was usual with television equipment of the time, it was big, heavy, and
very expensive. It also required a full time engineer to run it, oh, and the BBC had only one of
these machines (which lurked in what was called 'VT17', in the basement of Television Centre).

The above picture is of a spare HS100 magnetic disk still packed in its protective wooden transit
case. Mr Smith has made the last recording it contains of colour bars (naturally) visible by
'developing' it with a process that apparently included a special magnetic powder, petrol, and
gently banging the edge of the disk with a screwdriver (would you believe).

Bob Smith (who was that engineer looking after the machine) writes:

'The HS100 slow motion machine consisted of two large 15 inch diameter 3/8 inch thick
aluminium disks. The magnetic material is nickel cobalt with a thin coating of rhodium to protect
it from oxidation. These rotate at 3000rpm, so one field is recorded per revolution (3600rpm in
USA). Each head moves:- record -step-step-erase-record, in this way alternate tracks are
recorded thus when arriving at the center, the tracks in between can be recorded on the way out,
this means continuous recording is possible, if every track had been recorded on the way in then
the whole disk would have to be crossed, not possible in the time available, ( two fields 50
mS). On cessation of recording one step forward means the event 36 seconds ago (1800 fields)
is replayed, as the heads are moved by stepping motor rapid searching is possible, ideal for
sports replay.'

So now we know, many thanks Bob.

These lower two pictures are of the special record/replay head. This used a 'standard'
Quadruplex video head tip mounted in one corner of a ceramic triangle. The black cylinders
fixed to the other two corners are probably ferrite spacers that serve to stabilize the assembly.
This is not 'Winchester' technology and the head / spacers were in constant contact with the
3,000 RPM rotating disk.