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If the power supply is loaded too heavily, so as to possibly damage 01
,
the
voltage drop across R2 causes a potential difference to occur across the base and
emitter of 04.
However, this is only after the drop across R2 is sufficient to
exceed the contact potential of CR5, and CR5 becomes conductive.
Thus, this
circuit is inactive until a definite load is exceeded.
When 04 becomes conductive,
it takes control of the regulator circuit and causes the output voltage to drop with
increasing load. thus protecting the control transistor 01.
Resistors Rll, R12, and R13 are part of the A-B transfer circuit, other
components of which are wired into the main assembly.
NAI Era.e Coupler (3N)
(See Figure 31)
This is a very simple board which connects the eraSe power amplifier on
board 1 to the erase head and permits monitOring erase current.
120 kHz power
from the erase amplifier is supplied to terminal 20.
Cl forms a resonant circuit
with the erase head to provide maximum head cur rent.
Ll and C2 form a resonant
circuit at 240 kHz to shunt the second harmonic of the erase waveform around the
erase head.
Terminal 17 is connected to the head return which is isolated from
ground by 10 ohms in the erase amplifier chassis.
This point and the test point
connected to it becomes a monitoring point for 120 kHz current.
R3 permits erase
meter calibration.
M64 PAR 2-71
95/96
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