Akai AP-002 - Page 10

2. INOPERATIVE PITCH
As can be seen by the JIS specification summary
above, record sizes entail 3 kinds of specifications, and
these are classified into 2 categories which are directly
related to automatic return. These are 17 cm and
25/30 cm dimensions. For perception of return position
of there two kinds of records, in the case of in-
operative part of gear (less than 1 mm) the operating
principle of the perception equipment is as follows:
On a 17 cm record the last sound groove trace is in
the vicinity of 110%.
However, on a 30 cm record the sound groove has
already ended at the vicinity of 110% and the stylus
has passed the lead-out groove and is moving to the
last groove (concentric circle) at about this time
(1.8 mm radius).
Therefore, when the pick up arm comes to this vicinity,
if it is a 30 cm record, return operation must com-
mence, and if it is a 17 cm record, the last trace
must yet be effected. The difference in circumstances
of these two records lie in the volume of movement of
the stylus advancement within one single revolution.
In the case of a 17 cm record, because this pitch is
very limited (less than 1 mm), it is satisfactory if the
CLUTCH ASSY is kicked back by the protruding part
of the TABLE SHAFT ASSY as shown in Fig. 10
each time the record makes one revolution.
For details of this kicked back condition, refer to
Fig. 11. The gamma (y) (kick back volume) is about
0.6 m/m and on a 17 cm record even with a transport
pitch of 1 mm, the CLUTCH ASSY cannot retrieve
this kicked back portion.
Regardless of how many times the record rotates,
the transport pitch is less than 1 mm and the clutch
assembly continues to be kicked back. (Fig. 12) (Even
if the record is traced to about 97% vicinity (outside
of specifications), if the transport pitch is less than
1 mm, return will definitely not be effected during
the performance), (this occurs only when the TRIP
is pushed).
However, because practically all marketed records are
JIS ox equivalent, when the stylus advances to about
106% vicinity and moves to the lead-out groove, the
transport pitch suddenly increases (4 to 9 mm). When
this happens, the CLUTCH ASSY movement which
to now could not retrieve the 0.6 mm kick back
volume suddenly is increased (over 1.2 mm), and on
the next revolution when the protruding part ap-
proaches, meshing takes place and return begins.
In this manner the “speed displacement type return
mechanism utilizes the operating pitch and regardless
of whether the record is 17 cm or 30 cm, return is
effected at the end of record performance.
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3. FORCE (MANUAL) CUT
When listening to a record and you wish to stop in
the middle of a performance, or when playing a record
not according to specifications, and the stylus tip has
advanced to the last groove, simply bring the cut
lever forward. This moves PLATE REJECT 2 which
pushes PLATE JOINT (13), then POLE REJECT (15)
and ultimately CLUTCH ASSY (4) is pushed as shown
in Fig. 13. (= mark). Then return operation commences
and the power source is turned OFF (Refer to Item
1 above and Fig. 5).