Bias Osc Control Circuit; Record Control Circuit - Teac C-1 Service Manual

26
AMPLIFIER SECTION
6. OSC P.C.B.
6-1 BIAS OSC CONTROL CIRCUIT
Refer to Fig. 6.
Q833 is the OSC start-stop control transistor. Even if the
OSC is under power, the oscillator circuit does not operate
unless Q833 is on. R854, R855 and C807 of the base
circuit of Q833 determine ON/OFF times of OSC. (Refer
to Fig. 8)
The bias OSC circuit is powered from the constant voltage
+B
a
REC SAFE SAFETY Sw
sé69
ENABLE oo +10v
circuit Q830 to Q832. The OSC output level can be
changed by varing the supply voltage.
When the REC safety switch is set to the DISABLE posi-
tion, Q829 goes on, the constant voltage circuit does not
operate and OSC does not operate.
When the BIAS switch is set to the CrO2 (OPTION) posi-
tion, the bias can be adjusted from the front side of the
deck by R7 on the BIAS/EQ card.
BIAS
OUTPUT
osc PCB
T1317
Fig. 6 Bias OSC Control Circuit
6-2 RECORD CONTROL CIRCUIT
The record control circuit receives a REC signal and a REC
MUTE signal from the control PCB, and controls start-
stop of the BIAS OSC as well as turning on and off the
muting circuit of the recording amplifier. Refer to Fig. 7
and Fig. 8.
R362
INPUT—+4
+8
REC SIGNAL
R377 R378
OUTPUT
7
o
POWER MUTE
REC MUTE SIGNAL
T-1318
Fig. 7 Record Control Circuit