diode rectifiers which are mounted on heat
On germanium transistors, this voltage should
sinks, use the proper grade of silicon grease
be close to one-fourth volt. On silicon transis-
on mica insulators to insure proper heat trans-
tors, the voltage should be close to one-half
fer to the sink from the transistor body.
volt. In replacing power transistors or silicon-
Figure 4-2. Power
supply
PP-3940/G,
simplified
schematic
diagram.
voltage changes the base emitter voltage of
Detailed Function of Main Control
Q14 and Q15. If the output tries to rise, be-
Amplifier
cause of line or load change, the base of Q14
tends to rise and thus causes more current to
flow in this transistor. The emitters of Q14
A bridge circuit, consisting of R21-R25 and
and Q15 go to a higher potential. Since the
CR4, sensing in the output of the unit, con-
base of Q15 is held constant by reference di-
trols the first differential amplifier stage (Q14
ode CR4, this transistor tends to cut off. Less
and Q15). The base of Q14 varies with the
current will flow in Q15 and in collector resis-
output. Since the emitters of Q14 and Q15
tor R20. The collector of Q15 is now at a high-
are connected, any variation in the output
