HOM rev. new! Heathkit of the Month #26 - HP-23 AC Power Supply
Heathkit of the Month #26:
by Bob Eckweiler, AF6C
Heathkit HP-23A/B/C/E
AC Power Supply Family.
Introduction:
Many of the Heathkit HF and six-meter transceivers and twin radios were designed to run
either mobile or in a fixed location. Since these
are tube radios they require high voltage
power, and Heath decided to make the power
supply for these radios separate from the radio.
The savings in size and weight benefits its use
in mobile service. Two types of power supplies
were manufactured to support the Heath radio
line. The first type runs off household standard
AC power for home stations, and the second
runs off the car electric system, or other 13.8
volt DC auxiliary power system.
The UT-1 Power Supply:
Manufactured for only one year - 1960, this
power supply was introduced to power the
Heathkit Cheyenne MT-1 90 watt mobile AM
transmitter and Comanche MR-1 mobile receiver. It provides 300 volts for the receiver
and transmitter stages and 600 volts for the
final. By a simple change in wiring either 6.3
VAC at 8 amps or 12.6 VAC at 4 amps filament
power can be chosen. No negative bias voltage
is provided. The 600 volt output can supply up
to 200 ma and the 300 volt output can supply
up to 100 ma provided the total continuous
power drawn from those two outputs is 120
watts or less. The high voltage supply utilizes a
voltage doubler circuit with the half voltage tap
providing the low voltage output. Power output
is provided by a six blade Jones plug. The AC
line is well filtered with a pi filter in each lead.
The only controls on the unit are a power
switch and a pilot light. The UT-1 was replaced
by the HP-20 in 1961.
The HP-20 Power Supply:
Heath manufactured the HP-20 from 1961
through 1963. Circuit-wise it is very similar to
the UT-1 with the addition of -130V 30 ma bias
power. This is provided by an additional winding on the power transformer. The filament, LV
and HV power specifications are the same as
the UT-1. The only other change is the Jones
plug on the UT-1 is now an octal tube socket
type connector. This was most likely done for
cost savings. The bias power requirement was
driven by the release of the HX-20 mobile SSB
Transmitter and the HR-20 mobile SSB receiver. The HP-20 could be used in place of the
UT-1.
This month we'll look at the AC power supplies
that Heath manufactured for home use of its
various transceivers and twins. The early AC
power supplies run only on 120 VAC but later
they were updated with dual primary windings
on the power transformer so they can be used
on either 120 or 240 VAC. Prior to this Heath
made a separate 240 VAC 50 Hz supply for use
in Europe.
Copyright 2011, R. Eckweiler & OCARC, Inc.! Page 1 of 4
The HP-23 Power Supply:
In 1963 Heathkit introduced three single-band
200 watt PEP SSB transceivers. The HW-12,
HW-22 and HW-32 'Singlebanders' covering
80M, 40M and 20M respectively. With the
added power required by these rigs, a new AC
power supply was needed. Heath's answer was
the HP-23. This power supply has the same 9"
x 4-3/4" footprint as the HP-20 but is 3/4"
Radio
Introduced
Last Sold
Power Supplies
MT-1 / MR-1
1959
1962
UT-1, HP-20
HX-1 / HR-1
1962
1964
HP-20, HP-23 - 23A
HW-12/22/32
1963
1966
HP-23 - 23C, PS-23
SB-100
1965
1967
HP-23 - 23C, PS-23
HW-12A/
22A/32A
1966
1974
HP-23 - 23C, PS-23
SB-101
1967
1970
HP-23 - 23C, PS-23
HW-100
1968
1971
HP-23 - 23C, PS-23
SB-102
1970
1975
HP-23 - 23C, PS-23
HW-101
1970
1975
HP-23 - 23C, PS-23
SB-110
1965
1969
HP-23 - 23C, PS-23
SB-110A
1969
1971
HP-23 - 23C, PS-23
Table 1: Radio Power - Supply Matrix
Heathkit of the Month #26 - HP-23 AC Power Supply! HOM rev. new
taller. It supplies a high voltage of 820 volts at
no load dropping to 700 volts at 250 ma. Up to
150 ma may be drawn continuously or up to
300 ma at a 50% duty cycle. The low voltage
section supplies either 350 volts or 275 volts at
no load dropping to 300 volts or 250 volts at
150 ma (with a 100 ma load concurrently on
the HV section). A choke is used in the supply
to minimize AC ripple. Maximum continuous
current from the LV supply is 175 ma. The two
voltage ranges are selected by an internal wiring change. The fixed bias supplies -130 volts
no load dropping to -100V at up to 20 ma. is
capable of continuously supplying up to 30 ma.
An adjustable bias of -80 to -40 volts at 1 ma is
also available. The voltage is set by a screwdriver adjustable pot on the rear apron of the
power supply. Filament voltage is 12VAC at
5.5A with a center-tap to allow up to 11 A at
6.3V. Controls on the front panel are a power
switch and a neon pilot light. On the rear is the
power cord with a fused wall plug, adjustable
bias potentiometer and an eleven-pin tube
socket connector for power output. This power
connector includes two wires to allow the use
of a remote ON-OFF switch on the transceiver
itself which, if used, is in series with the power
switch on the front of the power supply. The
HP23 remained in production until 1968 when
it was upgraded to the HP-23A.
age section; the bleeder resistor was increased
from 50K! to 100K! and the power switch
was replaced with a three position switch that
allows selection of either of the two low voltages without the necessity to rewire the unit.
The pilot light was also removed. The HP23A
stayed in production until 1973 when it received some new changes and was renamed the
HP-23B.
The HP-23B Power Supply:
The HP-23B is more takeaway than addition.
Gone are the adjustable bias supply and the
center tap lead of the filament transformer;
now only 12.6 VAC filament voltage (at 5.5A) is
available. The addition is a three wire grounding AC plug and cord that replaces the two-wire
AC cord on the earlier units. The HP-23B remained in production from 1973 to 1978 when
the new HP-23C was introduced.
The HP-23E Power Supply:
Heath manufactured an European version of
the HP-23 with the model number HP-23E
that was designed for 240VAC 50 Hz AC
power.
The HP-23A Power Supply:
By 1968 Heathkit had more transceivers in
production that could use the HP-23 power
supply. This included the SB-100 and HW-100.
In 1968 Heath refined the HP-23 power supply
by adding dual primaries to the power transformer so the unit could run off of either 120 or
240 VAC, obsoleting the HP-23E. At the same
time the fuses were removed from the AC plug
and a circuit breaker was added to the chassis.
Small modifications were done to the low volt-
Page 2 of 4! Copyright 2011, R. Eckweiler & OCARC, Inc.
The HP-23C Power Supply:
The HP-23C continued the takeaway changes.
It no longer had the three position power
switch. Instead the power is only controlled by
the remote switch on the transceiver. The selection of the two levels of low voltage is again selected by a wiring change. In 1979 the HP-23
was replaced by the PS-23C.
The PS-23(C) Power Supply:
Sometime in early 1980 Heathkit renamed the
HP23C to the PS-23. Other than the name
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