Teac FD-55 Series, Maintenance Manual

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4-4-11. Check of Read Level
(A) Equipment
(1) Level disk
(2) SKA or userfs system
(3) Oscilloscope (not required when the SKA is used)
(B) Check procedure
(1) General method
(a) Use two channels of an oscilloscope and connect them to ^TP9 and TP10
(Differentiation amp.) on the PCBA MFD control.
Oscilloscope range 48tpi: AC mode, 0.5V
96tpi: AC mode, 0.2V
Set both channels, 1 and 2 to the above range. Set either of the
channels to Invert mode and ADD both channels.
(b) Start the spindle motor and install a level disk.
(c) Make the head move to the innermost track.
(d) Execute head loading.
(e) Execute 2F write operation for one rotation of the disk (250KHZ of
WRITE DATA frequency for DD-55A
a
, T, 500KHZ for FD-55G).
(f) Measure the average amplitude (Vp-p) of the read waveform as in
Fig.428.
(g) Calculate the read level by substituting the following expression
with the measured value in item (f ) and READ LEVEL calibration
value (see level disk label).
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