Heathkit IP 2718 Manual

Page 1

Model IP-2718

595-184006

\

' HEATH COMPANY ' BENTON HARBOR, MICHIGAN

Page 2

Heathkit® Manual

for the

TRI-POWER SUPPLY

Model IP-271 8

595484006

H EAT H C O M PA N Y Copyrlgm (e) um

HeathCompany
BENTON HARBOR, MICHIGAN 49022 AllHightsReserved

Page 12

Page 46

_HEATHKIT=

CIRCUIT DESCRIPTION

Refer to the Schematic Diagram (in the Illustration Booklet)
while you read this Circuit Description." The part numbers on
the Schematic are arranged in the following groups to help you
locate specific parts on the Schematic, Chassis, and Circuit
boards:

1- 99 Parts mounted on the chassis.

101 -1 99 Parts mounted on the circuit board, and in the
20-volt A' Supply.

201 -299 Parts mounted on the circuit board, and in the
20-volt 8' Supply.

The five principle sections of the Tri-Power Supply are the
power primary circuit, the S-volt supply, the 20-volt A' Supply,
the 20-volt 3' Supply, and the metering circuit.

PRIMARY CIRCUIT

The primary circuit of the Tri-Power Supply includes; hash-
fllter capacitor Ct across the line cord input, fuse F1, Power
switch SW1, pilot lamp PL1 and dropping resistor R1, Line
switch SW2, and transformer T1. The purpose of the Line
switch is to allow you to switch from 120-VAC operation to
240~VAC operation without rewiring the primary circuit of
power transformer T1 . To change from 120-VAC operation to

240-VAC operation, for example, you need only to push the
slide of switch SW2 to indicate the voltage that agrees with the
local AC service. CAUTION: Be sure never to have switch
SW2 at 120" during 240-volt operation; this could damage
the Power Supply. Three transformer secondary windings
provide separate voltage sources for the three voltage reg-
ulators of the 5-volt supply and the two 20-volt supplies.

5-VOLT SUPPLY

One secondary winding on transformer T1 provides a voltage
to rectifier diodes D1 and Dz. The rectified DC voltage is
filtered by capacitor 02. Resistor R4 is a current shunt for the
metering circuit. Resistor R2 is a bleeder resistor.

Regulation in the 5-volt circuit is accomplished in integrated
circuit lC1. The output voltage is fixed at 5 volts. The IC

provides internal overload, short-Circuit, and high temperature
protection. Capacitor C3 stabilizes the IC-regulator, and
capacitor 04 lowers the high-frequency output impedance.
Capacitor C5 provides an AC path to Chassis ground for vol-
tages induced when the 5-volt supply is used in the floating
mode of operation.