Teac FD-55 Series, Maintenance Manual

Page: 36 / 216

operation cannot be done) is installed, TP6 becomes HIGH level.
The voltage of TP6 should be more than 3V at masked notch and less
than 0.5V at open notch (write enable condition).
TP6 (File protect sensor)
Notch open
— 3.0V, M i n .
— — ___ 0.5V,Max.
Notch masked
(Fig.318) Typical waveform of TP6
(7) T P 7 , TP8 (Pre-amplifier)
Test: point to observe the read pre«amplifier output signals.
The pre«amplifier has two outputs of the order of several dozen to
several hundred mVp-p, and they differ in phase by 180° (opposite phase).
Both outputs are observed at TP7 and TP8 respectively.
For an accurate observation of the read waveforms, use two channels of
an oscilloscope with one channel set to Invert; mode and Add mode of
both channels. Use G (0V) test point for the oscilloscope ground.
TP7 and TP8 are used for checking various characteristics of the
read/write head and also for the check and adjustment of the head seek
mechanism such as track alignment.
TP7,TP8
(Pre-amp.)
5V,approx.
(Fig.319) Typical waveform of TP7 and TP8
(8) TP9, TP10 (Differentiation amplifier)
328