Here is a picture of an early vintage 1700 Series unit the 1700:
Here is another picture of the 1700:
Here is a picture of an early vintage 1700 Series unit the 1721L:
Here is a picture of an early vintage 1700 Series unit the 1722:
Here is a picture of an early vintage 1700 Series unit the 1722W:
Here are pictures of early 4 Channel Surround Sound Quad machines, most
in the 1700 Series, also the 202D-ss, not sure why the break with the numbering
tradition on that one... three pictures of the 1730D-ss:
Next is the Model 202D-ss, which reminds me of the GX-210D, but it is Quad.
It obviously has autoreverse, and works in 2 Channel or 4 Channel modes.
Here is a picture of an early vintage 1800 Series unit the 1800:
The early sets, in the "M" series, the "X" series, and the four
number series, like the 1710, 1722W, 1731, and 1800-SD, used the soft
metal permalloy type of heads, some with the 1 Micron Gap, which
showed extended frequency response. Some sets had moving head
assemblies, the "M" and the "X" series used the Crossfield Head concept
which Tandburg had made popular in Europe, which uses an additional head
applied on the reverse side of the tape, to supply just the "Bias Signal".
While the Crossfield technique was also used by others, it posed
certain alignment problems over the life of the unit, and I suspect
was largely abandoned by the late 1960's / early 1970's.
Some early Akai's had "Compute-O-Matic" a sort of motorized
compression feature, that turned down excessive recording levels
automatically. Still other sets, like the X-1800D had a cassette
recorder, or the X-1810D which had an 8 track tucked away in the
side of the set.
Here is a picture of an early vintage X-1810D unit:
The AKAI X-1810D is a Crossfield design, with three motors, but
still used the two function knobs as found in the 4000 Series.
Also note on the "X" knob, choice of tracks (3-2 Track, Stereo,
and 1-4 Track), it was a three speed design, (7 1/2, 3 3/4, 1 7/8),
with the SRT and an 8 Track Recorder in the right side. It weighed
in at almost 50 pounds.