Heathkit AA-151 User manual

STEREO APLIFIER
MODEL AA-15
1

RESISTOR AND CAPACITOR COLOR CODES
RESISTORS
The colored bands around the body of acolor coded resistor rep-
resent its value in ohms. These colored bands are grouped
toward one end of the resistor body. Starting with this end
of the resistor, the first band represents the first digit of
the resistance value; the second band represents the second
digit; the third band represents the number by which the first
two digits are multiplied. Afourth band of gold or silver rep-
resents atolerance of ±5% or ±10% respectively. The absence
of afourth band indicates atolerance of ±20%.
The physical size of acomposition resistor is related to its
wattage rating. Size increases progressively as the wattage
rating is increased. The diameters of 1/2 watt, 1watt and
2watt resistors are approximately 1/8”, 1/4” and 5/16",
respectively.
The color code chart and examples which follow provide the
information required to identify color coded resistors.
COLOR
BLACK -
BROWN -
RED
ORANGE
YELLOW
GREEN -
BLUE
VIOLET -
GRAY —
WHITE -
GOLD —
SILVER -
CODE
ST DIGIT 2nd DIGIT MULTIPLIER
0
l
z
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
I
10
100
1.000
10000
100.000
KOOO,000
—10.000.000
100.000.000
1000.000.000
.1
.01
TOLERANCE
GOLD ±5°7.
SILVER ±IO°7o
NO BAND ±20 °7
0
VIOLET-7
EXAMPLES
YELLOW- 447 x|,000
ORANGE-1,000-J (0R 47KO)
SILVER =TOLERANCE
±10 °70
RED-2
RED —
2
)22 x100,000
GREEN-100,000 J(oR 2.2 MEG.)
riTlwr^NO BAND TOLERANCE
±20 %
CAPACITORS
Generally, only mica and tubular ceramic capacitors, used
in modern equipment, are color coded. The color codes differ
somewhat among capacitor manufacturers, however the codes
shown below apply to practically all of the mica and tubular
ceramic capacitors that are in common use. These codes com-
ply with EIA (Electronics Industries Association) Standards.
MICA
COLOR CODE
IstPIGIT 2ndDIGIT MULTIPLIER TOLER °7o
BLACK—
BROWN —
RED
ORANGE-
YELLOW-
GREEN —
BLUE
VIOLET-
GRAY
—
WHITE —
GOLD
SILVER
~
0-
1-
2-
3-
4-
5-
6-
7-
6-
9-
0
1
2
3
4
5
6
7
6
9
I
10
-100
1000
10.000
-.01
±20
±2
±3
±5
±10
OBSERVE
DIRECTION OF
ARROW
WHT. OR
BLK. DOT
INDICATES
MICA
CHARACTERISTIC-
SEE NOTE IBELOW
(VALUE IN mjf— SEE NOTE 3BELOW)
EXAMPLE
27 X 100
\\I
RED VIOL RED
2,70 Ojjyf i5%
OR .0027 ufd
Place the
to right.
COLOR
TUBULAR CERAMIC
group of rings or dots to the left and read from left
CODE
1st DIGIT 2nd DIGIT MULTIPLIER
black-
brown -
RED
ORANGE-
YELLOW-
GREEN
BLUE
VIOLET
-
GRAY
WHITE —
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
I
10
—100
-1.000
10.000
TOLER.
TEMPERATURE
COEFFICIENT-
SEE NOTE 2
BELOW.
LESS OVLR 10
±20 ±20
±0.1 ±1
—
f
±2
—±2.5
±0.3 ±5
±0.25 —
±1.0 ±10
TEMPERATURE
COEFFICIENT-
SEE NOTE 2
BELOW
EXAMPLE
ORG ORG BLK GRN
14*;
33X1 ±5"X
33 uuf ±5%
(VALUE IN upf—SEE NOTE 3BELOW)
NOTES:
1. The characteristic of amica capacitor is the temper-
ature coefficient, drift capacitance and insulation resistance.
This information is not usually needed to identify acapacitor
but, if desired, it can be obtained by referring to EIA Stand-
ard, RS-153 (a Standard of Electronic Industries Association.)
2. The temperature coefficient of acapacitor is the predict-
able change in capacitance with temperature change and is
expressed in parts per million per degree centigrade. Refer
to EIA Standard, RS-198 (a Standard of Electronic Industries
Association.)
3.
The farad is the basic unit of capacitance, however cap-
acitor values are generally expressed in terms of pfd (micro-
farad, .000001 farad) and ppf (micro- micro-farad, .000001
pfd); therefore, 1,000 ppf =.001 pfd, 1,000,000 ppf =lpfd.
USING APLASTIC NUT STARTER
Aplastic nut starter offers a convenient method
of starting the most used sizes: 3/16" and 1/4”
(3-48 and 6-32). When the correct end is pushed
down over anut, the pliable tool conforms to the
shape of the nut and the nut is gently held while it
is being picked up and started on the screw. The
tool should only be used to start the nut.

TYPICAL COMPONENT TYPES
This chart is aguide to commonly used types of elec-
tronic components. The symbols and related illustra-
tions should prove helpful in identifying most parts and
reading the schematic diagrams.
RESISTOR
AVWV ^
POTENTIOMETER
(CONTROL)
—V\AM
—
t
CHASSIS GROUND NOT CONNECTED IELDED
CONNECTED 1tu

Assembly
and
Operation
of the
STEREO
AMPLIFIER
MODEL AA-151
HEATH COMPANY,
BENTON HARBOR,
MICHIGAN
TABLE OF CONTENTS
Specifications 2
Introduction 3
Circuit Description 4
Schematic 5*
Construction Notes 5
Parts List 6
Proper Soldering Techniques .8
Step-By-Step Procedure 10
Step-By-Step Assembly 11
Test And Connections 33
Final Assembly 35
Installation And Operation .35
In Case Of Difficulty 37
Service Information 38
Service 38
Replacements 39
Shipping Instructions 40
Warranty
Fold-out from page.
40
All prices are subject to change without notice. The Heath
Company reserves the right to discontinue instruments and
to change specifications at any time without incurring any
obligation to incorporate new features in instruments pre-
viously sold.
1
asubsidiary of
DAYSTROM, INCORPORATED Copyright 1961
Heath Company 10/12/62

SPECIFICATIONS
Page 2
Power Output
Rated Power (rms): ...
Peak Power:
Circuit:
Power Response:
Tone Controls
Bass:
Treble:
Maximum Harmonic Distortion (both channels at
full output).
30 cycles:. .
1kc:
15 kc:
Intermodulation Distortion (maximum):
(Using 60 cycle and 6kc signal mixed 4:1.)
Input Sensitivity
MAG. PHONO:
TUNER-AUX.:
XTAL:
Channel Separation:
Hum And Noise
MAG. PHONO:
XTAL-TUNER-AUX.:
Damping Factor:
Tube Complement:
14 watts per channel, 28 watts monophonic.
28 watts per channel, 56 watts monophonic.
Features Heath patented Ultra-Linear circuit,
U.S. Patent #2, 710, 312.
±1 db from 30 to 15,000 cps at 14 watt level.
19 db boost at 30 cps. 17 db cut at 30 cps.
13 db boost at 15,000 cps. 17dbcut at 15,000 cps.
2%.
*7%.
2%.
2%, both channels at full output.
.004 volt for 14 watts output.
Vt '*
'
.2 volt for 14 watts output.
.25 volt for 14 watts output.
Better than 35 db.
55 db or better below 14 watts.
65 db below 14 watts.
10.
2-6EU7
2-6AU6
2-6AN8
4-EL84/6BQ5
1-GZ34/5AR4

Page 3
Controls And Switches:
AC Receptacles:,
SOURCE Selector (MAG. PHONO, XTAL PHONO,
TUNER, AUX.)
VOLUME (dual-concentric with clutch).
BASS (dual-tandem).
TREBLE (dual-tandem).
MODE Selector (AMP LEFT, AMP RIGHT,
MONO LEFT SOURCE, MONO RIGHT SOURCE,
STEREO, and STEREO REV.)
POWER (ON-OFF).
SPKR. PHASE (NORM.-REV.)
FILAMENT BALANCE (LEFT CHANNEL and
RIGHT CHANNEL).
1-NORMAL (unswitched), 3amps maximum.
1-SWITCHED, 1amp maximum.
Power Supply:,
Power Requirements:
Transformer-operated full- wave rectifier.
117 volts AC, 50/60 cps, at 130 watts.
Dimensions
Overall: 5-1/4” high x15” wide x11” deep.
Clearance required for rear apron
connections: 1-1/4”.
Net Weight:, 25 lbs.
Shipping Weight:, 28 lbs.
Features patented Heath Ultra-Linear® circuit
U. S. Patent #2,710,312
INTRODUCTION
Your HEATHKIT Model AA-151 Stereo Ampli-
fier is, effectively, two high fidelity amplifiers,
two preamplifiers and apower supply, all con-
tained in asingle, attractively styled vinyl-
clad cabinet. Quality, versatility, styling, and
economy are the keynotes of the AA-151 design.
The use of two independent power amplifiers and
preamplifiers as asingle unit provides excellent
performance versatility, which could not be dup-
licated using separate amplifiers and preampli-
fiers occupying the same amount of space as the
AA-151. Either eight monophonic or four stereo
signal sources can be connected to the input jacks
of the AA-151. Each input source can then be
selected individually with the SOURCE selector
switch. The output level of the power ampli-
fiers may be set separately or simultaneously
with the clutched VOLUME control.

HEATMKIT b
Page 4DA
fiTROM
CIRCUIT DESCRIPTION
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LEFT CHANNEL PREAMPLIFIER
ai•)i*ii*MIiiiiit•»i iM11)iMivf
IUMII I1IMIHI iII l< Ml
LEFT CHANNEL POWER AMPLIFIER
h-
3
CL
z
:z
-z
:<
-i
:u
AUX
TUNER
XTAL PHONO
:“MAG. PHONO
y
t
VCW
y
6EU7
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SOURCE
SELECTOR MC
SELE'
IDE 1
CTOR |
VI B1/2 6EU7 TONE CONTROL jV6 6AN6 V7 EL 84
V3 6AU6 NETWORK !1ve EL84 LEFT
"SPEAKER
i•11•i*1111m11*»11111 1 1 1 11111111»111111111111111*
£». I I IIIIIfII II«IIII1II•III III»1II I tI»I»II«»M«I4 I IIIIt I1(ItI•IiIII*IMt
-to
tHAUX
:o.
:z
=uJ TUNER
:z
:z
-<
E5XTAL PHONO
:h
:5
:gMAG. PHONO
-0£
RIGHT CHANNEL PREAMPLIFIER
t
CW V2B 1/2 6EU7
V4 6AU6 [TONE CONTROL
NETWORK
ll lIIIill 1IIIII I*Iit I I I I II IIII IIIt 11II II) II«IM1 I 1
»
RIGHT CHANNEL POWER AMPLIFIER
L| V5 6AN8 |—»|
V9 EL84
V10 EL84 RIGHT
SPEAKER
V2A 1/2 6EU7
11i11>t11111i•111 1 ii i •1111111r111iii i•i«i11111it1 1 1ii11•1 1 ii111
1
11111i1111«) 1111 i t1111111
»
it11ai1111it11•11»iii tiin1111i»11«iia1
1
«1 1 1m1111111i1 1 1111 < 11111111
1
«i
BLOCK DIAGRAM
The Model AA-151 Stereo Amplifier has three
basic sections; acommon power supply, the
left channel preamplifier and amplifier, and the
right channel preamplifier and amplifier.
The left and right channel preamplifier and
amplifier circuits are identical, therefore, only
the left channel and power supply circuits will
be discussed. For the purpose of this description,
assume that the SOURCE switch is in the MAG.
PHONO position and that the MODE selector
switch is in the LEFT AMPposition. We suggest
that you frequently refer to the Schematic and
Block Diagrams.
The audio signal presented to the MAG. PHONO
input is applied directly to the grid of tube VIA.
VIA is ahigh-gain, low-noise preamplifier stage.
The amplified signal is coupled from the plate
of VIA through capacitor C5 to the grid of VI B.
Resistors R9 and RIO, along with capacitors
C3, C4 and C6, provide RIAA equalization for
magnetic phono cartridges. VI Bis also ahigh-
gain preamplifier. The amplified signal from its
plate is coupled by capacitor C8 and the VOL-
UME control to the grid of V3.
V3 further increases the amplitude of the sig-
nal. The amplified signal from V3 is fed through
capacitor Cll to the packaged electronic tone
control network. This network consisting of sev-
eral resistors and capacitors, encapsulated in
an insulating material, operate in conjunction
with R20 and R23 to perform the BASS and
TREBLE control functions. The output signal of
the tone control network is applied through the
MODE switch to the grid of V6A.
The signal is again amplified by V6A and is
applied to the grid of V6B, the phase inverter
V6B does not amplify the signal, but applies
the signal in proper phase, to each tube (V7
and V8) in the push-pull amplifier output stage.
The signal from the push-pull output stage is
coupled through audio output transformer T1
to the left channel speaker system.
The power supply uses a5AR4 tube as afull-
wave rectifier. The filter network, consisting
of capacitors C25, C24, C23, and C22, and re-
sistors R36, R35, and R34, removes the 120
cycle ripple from the B+ voltage.

CONSTRUCTION NOTES
Page 5
This manual is supplied to assist you in every
way to complete your kit with the least possible
chance for error. The arrangement shown is
the result of extensive experimentation and
trial. If followed carefully, the result will be a
stable instrument, operating at ahigh degree
of dependability. We suggest that you retain the
manual in your files for future reference, both
in the use of the instrument and for its main-
tenance.
UNPACK THE KIT CAREFULLY AND CHECK
EACH PART AGAINST THE PARTS LIST. In so
doing, you will become acquainted with the parts.
Refer to the charts and other information on the
inside covers of the manual to help you identify
the components. If some shortage or parts
damage is found in checking the Parts List,
please read the Replacement section and sup-
ply the information called for therein. Include
all inspection slips in your letter to us.
Resistors generally have a tolerance rating of
10% unless otherwise stated in the Parts List.
Tolerances on capacitors are generally even
greater. Limits of +100% and -20% are common
for electrolytic capacitors.
We suggest that you do the following before work
is started:
1. Lay out all parts so that they are readily
available.
2. Provide yourself with good quality tools.
Basic tool requirements consist of ascrew-
driver with a1/4” blade; asmall screw-
driver with a 1/8” blade; long-nose pliers;
wire cutters, preferably separate diagonal
cutters; apen knife or atool for stripping
insulation from wires; asoldering iron (or
gun) and rosin core solder. Aset of nut
drivers and anut starter, while not neces-
sary, will aid extensively in construction of
the kit.
Most kit builders find it helpful to separate the
various parts into convenient categories. Muffin
tins or molded egg cartons make convenient
trays for small parts. Resistors and capaci-
tors may be placed with their lead ends in-
serted in the edge of apiece of corrugated
cardboard until they are needed. Values can
be written on the cardboard next to each
component. The illustration shows one method
that may be used.

PARTS LIST
Page 6
PART PARTS DESCRIPTION PART PARTS DESCRIPTION
No. Per Kit No. Per Kit
Resistors 4Capacitors (cont’dt)
1-9 41000 ft 1/2 watt 25-42 130-30 jutfd at 350 volts twist
(brown-black- red) prong electrolytic
1-13 42700 ft 1/2 watt 25-55 250 jufd at 10 volts miniature
(red-violet- red) electrolytic
1-22 522 Kft 1/2 watt 25-85 150 /ifd at 25 volts tubular
(red-red- orange) electrolytic
1-23 227 Kft 1/2 watt 25-101 160-25 /xfd at 500-450 volts
(red-violet- orange) twist-prong electrolytic
1-24 533 Kft 1/2 watt
(orange- orange- orange) Controls-Switches
1-88 436 Kft 1/2 watt 10-61 2200 ft tab- mount control
(orange-blue-orange) 12-34 11megohm dual-concentric
1-25 247 Kft 1/2 watt control
(yellow-violet- orange) 12-35 21megohm dual-tandem con-
1-26 5100 Kft 1/2 watt trol
(brown-black-yellow) 60-2 1DPDT slide switch
1-27 3150 Kft 1/2 watt 63-249 1AC switch
(brown-green-yellow) 63-258 14-position, single- section
1-29 4220 Kft 1/2 watt rotary switch
(red-red-yellow) 63-259 16-position, single- section
1-30 2270 Kft 1/2 watt rotary switch
(red-violet- yellow)
1-33 10 470 Kft 1/2 watt Transformers
(yellow-violet- yellow) 51-29 2Audio output
1-34 2680 Kft 1/2 watt 54-93 1
*r
Power
(blue -gray-yellow)
1-35 21megohm 1/2 watt
(brown-black-green) Terminal Strips-Sockets
1-37 22.2 megohm 1/2 watt 431-1 6Dual 1-lug terminal strip
(red- red-green) 431-2 22-lug terminal strip
4-2 2100 Kft 1/2 watt LOW-NOISE 431-3 33- lug terminal strip
(brown-black-yellow) 431-5 6 4- lug terminal strip
1A-2 11000 ft 1watt 431-13 14- lug screw type terminal
(brown-black-red) strip
IB-2 14700 ft 2watt 431-17 15- lug screw type terminal
(yellow-violet- red) strip
3G-9 1100 ft 7watt wire-wound 431-27 33-lug terminal strip
Capacitors 434-15 27-pin wafer tube socket
21-3 210 disc ceramic 434-16 49-pin wafer tube socket
21-7 633 jitjLLf disc ceramic 434-20 2AC socket
21-85 256 /Ltjuf disc ceramic 434-58 1Octal tube socket
21-39 2.0035 /ifd disc ceramic 434-68 49-pin molded tube socket
21-42 1.01 jufd disc ceramic 1.6 kv 434-76 2Triple phono socket
21-47 2.01 /ifd disc ceramic 434-82 1Double phono socket
21-82 1.02 /ifd disc ceramic
23-50 2.022 /ifd tubular Tubes- Lamp-Fuses
23-52 .2.047 /ifd tubular 411-11 26AU6 tube
23-61 4.05 /ifd tubular 411-68 26AN8 tube
23-28 8.1 /ifd tubular 411-108 4EL84 tube

PART
No. PARTS
Per Kit DESCRIPTION
Tubes-Lamps-Fuse (cont’d.)
411-136 1GZ34/5AR4
411-143 26EU7 tube
412-13 1Red neon pilot lamp
421-3 12-amp slow-blow fuse
Hardware
250-8 '16 #6 x3/8” sheet metal screw
250-10 46-32 x1/2” truss head ma-
chine screw
250-49 20 3-48 x1/4” screw
250-56 40 6-32 x1/4” screw
250-89 22 6-32 x3/8" screw
250-106 26-32 x3/8" self-tapping
screw
252-1 20 3-48 nut
252-3 64 6-32 nut
252-4 12 8-32 nut
252-7 6Control nut
252-32 1Push-on speednut
254-1 72 #6 lockwasher
254-2 12 #8 lockwasher
254-4 10 Control lockwasher
254-7 20 #3 lockwasher
255-1 21/8" spacer
259-11 1Spade lug
Wire-Knobs
89-1 1Line cord
340-1 1Length bus wire
341-1 1Length heavy black wire
343-6 1Length shielded audio cable
344-1 2Length hookup wire (light and
dark color)
346-1 1Length sleeving
347-9 1Length 3- conductor shielded
cable
462-117 1Small black knob 3/4" x5/8"
462-118 1Clear plastic knob l-i3/16”
x13/32"
PART PARTS
No. Per Kit DESCRIPTION
Wire- Knobs (cont’d.)
462-119 1Small black knob 3/4" x5/8"
for .187 diameter shaft
462-124 4Black and clear plastic
cascaded knob
Sheet Metal
90-M166 1
200-M296F469-470 Cabinet
1
203-M234F467 Chassis
1
203-M235F468-498 Control panel
1Front panel
203-M236 1Subpanel
204-M366 1Left front panel support
bracket
204-M367 1Right front panel support
bracket
205-
M296 1
206-
M176F471 Bottom plate
1Center shield
210-14 1Front bezel
Miscellaneous
75-20 1Insulated plate for double
phono socket
75-24 1Line cord strain relief
75-41 2Insulator for triple phono
socket
84-23 2Packaged Electronic Circuit
(P.E.C.) tone control net-
work
206-3 2Tube shield
206-55 2Tube base shield
261-17 4Plastic foot
391-11 1Nameplate
423-1 1Fuse holder
481-1 1Metal capacitor mounting
wafer
481-4 1Fiber capacitor mounting
wafer
331-6 Solder
595-421 1Manual