Fostex B-16 - Page 14

UB-I
J1Q-1
REC hec rec Fig. 4.2
is output from J10-2.
When the REC button is depressed, "L" level is input to Ul-0 and ul-10 goes
to "H" level. D flip-flop U6 is inverted by this output, U6-2 goes to "L"
level, Q13 switches off and an ENCODE signal is output from J10-2.
When the REC button is depressed again, D flip-flop will invert again and Q13
switches on and a DECODE signal is output from J10-2 . When the ENCODE signal
is output and the INPUT MON switch is at INDIV (not depressed) , the
INPUT MON LED will blink and the input signal of the channel whose RECORD
SELECTOR switch is depressed, will be monitored.
4.4 Capstan motor drive circuit
When the transport is in other than the PLAY and REC modes, Q25 will be ON,
and therefore Q27 will also be ON, Q20 is then switched OFF and U13-3 will go
to approximately OV. Therefore, the capstan motor will not be driven, when the
transport enters the PLAY or REC mode, Q25 switches OFF, Q28 switches ON, a
high voltage will be applied to J24-3 and the capstan motor will be driven.
A tach generator output of about 2400Hz is applied to U13-12 and output from
U12-14 as a square wave. This square wave is differentiated by C32 and R132,
and Q26 is switched ON by the rising edge of this waveform.
As Q21 and Q22 are constantly in the ON state, the integration circuits of
R309, R136 and C331, C34 are always functioning. Therefore, the saw tooth
wave generated by this integration circuit and by the on/off of Q26, is applied