Heathkit IM 4180 Manual

Page 1

HEATHKIT®
MANUAL

HEATH COMPANY - BENTON HARBOR, MICHIGAN

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HEATH COMPANY PHONE DIRECTORY
The following telephone numbers are direct lines to the departments listed:
Kit orders and delivery information . ..................... (616) 982-3411

Credit .............. . . (616) 982-3561
Replacement Parts . . . . . (616) 982-3571

Technical Assistance Phone Numbers
8:00 AM. to 12 RM. and 1:00 PM. to 4:30 PM EST, Weekdays Only
Fl/C, Audio, and Electronic Organs . . (616) 962-3310

Amateur Radio . . (616) 982-3296
Test Ewipment, Weather Instruments and

Home Clocks ....................................... (616) 982~3315
Television ............................................ (616) 9824307

Aircraft, Marine, Security, Scanners, Automotive,
Appliances and General Products .
Computers .........................

c . . (616) 982-3496
. (618) 982-3309

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YOUR'HEATHKIT 90 DAY LIMITED WARRANTY

If you are not satisfied with our service . warranty or otherwise - or with our products, write directly to our Director of Customer
Services, Heath Company, Benton Harbor, Michigan 49022. He will make mrlain your problems receive immediate, personal
attention.

Our attorney, who happens to be quite a kitbuilder himself, insists that We describe our warranty using all the necessary legal
phrases in order to comply with the new warranty regulations. Fine. Here they are:

For a period of ninety {90) days after purchase, Heath Company will replace or repair free of charge any parts that are defective
either in materials or workmanship. You can obtain parts directly from Heath Company by writing us at the address below or by
telephoning us at (616) 932-3571. And well pay shipping charges to get those parts to you - anywhere in the world

We warrant that during the first ninety [90] days after purchase. our products, when correctly assembled, calibrated, adjusted
and used in accordance with our printed instructions, will meet published specifications.

If a defective part or error in design has causad your Heathlrit product to inaliunction during the warranty period through no
fault of yours, we will service it free upon proof of purchase and delivery at your expense to the Heath factory, any Heathkit
Electronic Center (units of Schlumberger Products Corporation), or any of our authorized overseas distributors.

You will receive free consultation on any problem you might encounter in the assembly or use of your Heathkit product. Just
drop us a line or give us a call. Sorry. we cannot accept collect calls.

Our warranty does not cover and we are not responsible for damage caused by the use of corrosive solder, defective tools.
incorrect assembly, misuse. fire. or by unauthorized modifications to or uses of our products for purposes other than as
advertised. Our warranty does not include reimbursem-t for customer assembly or set-up time.

This warranty covers only Heathkit products and is not extended to allied equipment or components used in conjunction with
our products. We are not responsible for incidental or consequential damages. Some states do not allow the exclusion or
limitation of incidental or consequential damages, so the above limitation or exclusion may not apply to you. This warranty
gives you specific legal rights, and you may also have other rights which vary from state to state.

HEATH COMPANY
BENTON HARBOR, Ml. 49022

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Prices and specifications subject to change without notice.

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Page 41

INITIAL TESTS

RED WIRE

CIRCUIT BOARD
PIN

PICTORIAL 5-1
Refer to Pictorial 5-1 for the following steps.
( V5 Prepare both ends of the remaining red wire.

' K
( 4] Push a male circuit board pin onto one end of
the wire as shown. Solder the connector to the
wire. The wire will be used for tests in the
following steps.

NOTE: In any of the following steps in this section, or
in Calibration or in the Alignment" sections,
when a jumper wire is referred to, for example, a
blue jumper wire or a red jumper wire," it means
you should locate and connect one of the jumper
wires (with a female connector] to a male connector
pin on the circuit board.

Refer to Pictorials 5-2 and 5-3 (Illustration Booklet,
Page 9] for the following steps.

('\/{ Connect the male pin on the end of the red test
wire into the female connector on the end of the
green jumper wire.

0/) Connect the battery clip on the main circuit
board to the battery case if you are using bat-
teries; if you are going to use the Battery
Charger/Eliminator Accessory, connect the
small plug on that unit into 1101 on the main
circuit board. Make sure the AC line cord is
plugged into an AC outlet.

If you have installed rechargeable batteries, set
switch SW102 at CHARGE; the switch position,
otherwise. must be set to NO CHARGE.

( V On the front panel, press the RED ON-OFF

switch to its OFF position (out).
,

V) Check the position of the meter pointer. If the
pointer is not exactly over the scale 0, turn
the mechanical adjust screw [directly under the
center of the meter] until it is one pointer width
below 0."

[ ) On the main circuit board connect the five re-
maining jumper wires as follows:

Yellow jumper wire to NORM.

Orange jumper wire to NORM.

Blue jumper wire to NORM.

Violet jumper wire to NORM.

Red jumper wire to NORM.
NOTE: In the following tests, if you fail to obtain the
desired results, push the ON-OFF PUSHBUTION to
OFF (out) and refer to the In Case of Difficulty
section on Page 51.

(IV/l; Set the front panel controls as follows:

0 AUDIO LEVEL: Counterclockwise,
but not OFF.

v" ON-OFF switch: ON (In).
BATT switch: Pushed in.

( Vj Touch the end of the red test wire to the 15V pin
near U108. Check the meter lower scale for a
reading between 10 and 15.

[ W Touch the red test wire to the 8V pin near U108.
Check the meter for an upscale reading. As you
hold the wire on the 8V pin, adjust 8V ADI
control R186 to obtain a reading of approxi-
mately 7.5 on the lower meter scale.

( ) Push the ON-OFF switch to OFF.

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Detail 5- 3A-

(I/) U107: Refer to Detail 5~3A and identify the pin 1
end of the TBABZDL (#442-610) integrated
circuit. Be sure the pins are straight on the IC;
then match the pin 1 end of the IC with the
index mark on the circuit board and carefully
push the 1C into socket U107 as shown.

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Page 57

CIRCUIT DESCRIPTION

A number series has been assigned to the circuit com-
ponents mounted on the chassis and on the circuit
boards. These numbers are referred to throughout the
sections of the Manual to help you locate and identify
the components. These components are grouped as
follows:

1-99 Parts mounted on the chassis.
101-199 Parts mounted on the main
circuit board.
201-299 Parts mounted on the converter

circuit board.

Refer to the Block Diagram (Illustration Booklet, Page
10) and to the fold-in Schematic Diagram as you read
this Circuit Description.

GENERAL

RF signals from a signal generator or a transmitter are
coupled to the RF Input jack on the FM Deviation
Meter by shielded cable, a wire, or through an acces-
sory antenna. The RF signals are routed into the con-
verter assembly where they are mixed with a local
oscillator signal, the frequency of which is .2 MHz
above or below the incoming signal. The two signals
are mixed with the output of a harmonic generator
and are coupled through a preamplifier and an IF
amplifier.

The amplified IF signal is then coupled through a
limiter and a waveshaper circuit in which the signal
is formed into a square wave to drive a trigger circuit.
The trigger output feeds into a monostable multivib-
rator whose duty cycle varies according to the devia-
tion frequency. The output of the multivibrator passes
through two stages of low-pass filters to produce a
demodulated audio signal. The audio signal is then
routed in two directions. In one direction, the signal
goes through a switch attenuator network, a peak
detector, and is coupled to the output meter. Routed
in the other direction, the audio signal is passed
through a de-emphasis network, across a level con-
trol. and into an audio amplifier. The output of the
audio amplifier is coupled directly to a speaker [or
head-phone] jack on the front panel.

Power is supplied to the Meter circuits from ten
NEDA Type 15 (AA) batteries or from a Battery
Charger/Eliminator Accessory. Fifteen-volt power is
taken directly from the power source. Eight-volt
power for the integrated circuits is obtained from an
integrated circuit regulator and a filter.

CONVERTER CIRCUITS

A dual-gate MOSFET, 0202, is a variable frequency
oscillator. Coil LZOZB resonates with tuning capacitor
C212 to determine the oscillator frequency. Coil
LZOZB provides positive feedback to 0202 gate 1 [G1].
Fine tuning is provided by control R3 and variable
capacitance diode D201.

Transistor 0201 is a harmonic generator. The oscil-
lator signal from the drain [D] of 0202 is DC coupled
into the base [B] of 0201. Capacitor C201 in the emit-
ter [E] circuit of 0201 stores a charge to keep the
transistor turned off the greater part of each cycle. 0n
negative excursions of the signal at the base of 0201,
the collector conducts short, high-harmonic current
pulses.

A hot-carrier diode, D202, is a frequency converting
mixer. The current pulses from the collector of 0201
are coupled to the anode of D202 and the incoming RF
signals are coupled to its cathode. The derived inter-
mediate frequency (IF) signal is created in a low-pass
filter consisting of coil L201, resistor R201, and
capacitor C202.

IF CIRCUITS

IF signals are coupled from the output of the conver«
ter circuit to the (IF) Gain control. The attenuated IF
signal is then routed into the base of preamplifier
transistor 0101 on the main circuit board. Transistor
0101 is a low-noise preamplifier with a gain of 10. Its
collector output is coupled through capacitor C104
and into pin 3 of operational IF amplifier integrated

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circuit U101. U101 is a wideband amplifier with a
gain of 80. The IF signal, as it is coupled from output
pin 6 of U101 to the input of U102, is routed across a
limiter network consisting mainly of diodes D101 and
D102. This limiter circuit removes the peaks from the
IF signal and effectively creates square waves from it
for most input signal levels.

The square-wave signal is routed into operational
amplifier IC U102 pin 3 which functions as a
waveshaper and squelch circuit. Positive feedback
from C115 causes the output square wave from pin 6
to switch up and down very rapidly. An offset bias on
the input from the limiter diodes provides a squelch
action for low-level signals.

Transistor Q102 functions as a trigger circuit. Positive
current spikes are coupled into the base of Q102
through capacitor C116. The collector output is
positive-going trigger pulses; which are coupled to
integrated circuit U103 through capacitor C118 and
resistors R131 and R132. Operational amplifier IC
U103 is a monostable multivibrator whose output is
normally low. When a trigger pulse from 0102 is
present on input pin 2, its output rises. Regeneration
is provided by capacitor C121 to input pin 3 through
resistor R136. The output pulse width at U103 pin 6 is
set to approximately 1.6 us by Calibration (CAL) con-
trol R138.

Two operational amplifier ICs, U104 and U105, are
low-pass filters. The inputs to the filters are pulses of
fixed width and amplitude with spacing that varies
according to the deviation frequency,

AUDIO CIRCUITS

The pulses are integrated andldemodulated by the
low-pass filter network and, at the output, are the FM
audio signals. A resistive voltage divider consisting
of resistors R156, R157, and R158, form a range di-
vider. The demodulated signal coming from U105 pin
6 is a full-scale 7.5 kHz signal. At the junction of
resistors R156 and R157, the signal is 20 kHz full-
scale, and at the junction ofR157 and R158, the signal
is 75 kHz full-scale.

The 2 kHz range uses the same signal as the 7.5 kHz
range, but the gain of the peak detector is changed by
switching resistor R161 into the circuit, along with
low-pass filter resistor R155 and capacitor C138.

V_HEATHK1T

Operational amplifier IC U106 is a peak detector
whose input is a signal selected by the range switch
attenuator circuit. The output of U106 is rectified by
diode D107 and the signal is stored in capacitor C143.
The direct current developed at the output of U106
flows through the meter and develops a negative
feedback voltage across resistor R167. Resistor R161
shunts resistor R167 to reduce negative feedback on
the 2 kHz range.

AUDIO OUTPUT

Resistors R152 and R153 with capacitor C1 form a
de-emphasis circuit. Audio signals coming from IC
U105 are routed into both resistors and through one of
them, as determined by the setting of De-emphasis
switch SW1, and on into capacitor C1 and Audio
Level control R4.

Audio signals from the center tap of control R4 are
routed to U107 pin 7. The amplified audio output
signal is coupled from U107 pin 12 through capacitor
C149 to the primary winding of audio transformer
T101. Audio output signals are coupled from the sec-
ondary winding of T101 to the output Speaker jack 14
on the Deviation Meter front panel. Switch SW2 is
ganged onto the shaft of Audio Level control R4.
When control R4 is turned fully counterclockwise,
SW2 turns off the power to the audio amplifier circuit
to conserve battery energy.

POWER SUPPLY

Power for the FM Deviation Meter is taken from ten
Type AA (NEDA Type 15) batteries and (or) an op-
tional Battery Charger/Eliminator Accessory. Zinc-
carbon or alkaline non-rechargeable cells with a use-
ful life of approximately 80 hours may be used with-
out the Charger/Eliminator pack, or rechargeable
nickel-cadmium batteries may be used for a charged
useful period of approximately 35 hours. These bat~
teries are optional as the Deviation Meter can operate
directly from the accessory power pack with no bat-
teries at all. The 15-volt power source is taken directly
from the battery or power pack through On-Off switch
SW101A contacts. Power for the 8-volt supply also
comes from this source.