Heathkit GP 11 Schematic Manual

Page 1

CIRCUIT DESCRIPTION

To better understand how the Power Supply works, follow the
circuit on the Schematic Diagram while reading this description.

DC source voltage is applied to the INPUT terminal, and via a
hash filter network consisting of choke RFCl and capacitors C1
and C2, to the vibrator. The Power Supply can be wired to oper-
ate from either a 6-v01t or 12-v01t DC source. In either case, the
vibrator coil is Operated from 6 volts. For 12-volt operation,
resistor R1 is used in series with the vibrator coil to drop the
voltage applied to the coil to 6 volts. For 6-volt Operation, a wire
is connected across resistor R1, and 6 volts is applied directly
to the vibrator coil,

The vibrator acts as a mechanical switch, alternately con-
necting and disconnecting the voltage source to opposite ends of
the transformer primary winding at a rate of approximately 115
cps. This results in a rectangular waveform. which, due to the
step-up effect of the transformer, appears as a high AC voltage
in the secondary winding. By using different primary winding
taps for 6-volt and 12-volt operation, the step-up ratio of the
transformer can be changed so that the same secondary AC
voltage results in either case. Buffer capacitor CS is connected
directly across the secondary winding.

AC voltage is applied from the secondary winding, through ca-
pacitor C7 to silicon diodes D1 and D2. These diodes with ca-
pacitors C7 and C8 are arranged in a half-wave voltage-doubler
circuit. Choke RFCZ and capacitor C9 provide hash filtering for
the B+ voltage as it is applied to the B+ output terminal.

l2-VOLT

RED-YEL

O

.- 0 GROUND

ViBRATOR

RFCI

@ m u. I @
oil"
.5 UJ'D .0! LIFO

O Dc INPUT

SCHEMAIIC DIAGRAM

MOON. OP-II

VIBRATOR POWER SUPPlY