is terminated in resistive load R44.
When an extension speaker is
connected to J3 audio is coupled to the external speaker and contacts
of J3 open to disconnect the internal speaker.
Drive from Q10, Q11 and Q8, Q9 halves of the power amplifier
may be slightly unbalanced due to transistor parameters and difference:
in other circuit parameters.
C27, C26, R36, and R34 establish the
operating point of Q10, Q11 with respect to Q8 and Q9.
trol R36 adjusts the operating point so that equal drive is obtained
from each half of the power amplifier.
Input amplifier Q7 is operative only during playback when
reverse bias is removed by contacts of RECORD switch S6 to R41 and
This forward biases the amplifier into normal operation. In
RECORD, B+ is applied to reverse bias the stage and disable the
Primary power is applied through plug P1, POWER OFF switch
S1, and fuses F1 and F2 to power transformer T1 and to the tape drive
Ac voltages induced in the two secondaries of T1 are recti-
The dc output of A2 is filtered
by C41 and applied to dynamic brake section of the tape drive circuit.
The dc output of rectifier Al is filtered by C39 and is applied to
series regulator Q12.
The base voltage of Q12 is clamped to a reference
If, the output voltage tends to
voltage of 30 volts by zener diode VR1.
decrease, the emitter of Q12 tends to become less positive with respect
The emitter to collector
to the base, increasing the forward bias.
impedance then decreases, increasing the output voltage.