Heathkit Heathkit SG-8 Manual

ASSEMBLING
AND USING
SIGNAL
GENERATOR
MODEL 3G-8
HEATH COMPANY
BENTON HARBOR,
MICHIGAN
ASSEMBLY AND OPERATION OF THE
HEATHKIT SIGNAL GENERATOR
MODEL SG-8
SPECIFICATIONS
Frequency Range
Band А............. rennen ernennen 160 ke to 500 Кс
Band B............. ca Lo 900 ke to 1650 ke
Band с............. a nr... 1.65 mc to 6.5 me
Band D..... o Lara. а кола 0.9 me to 25 me
Band E............... Lor ooo... 29 mec to 110 me
Calibrated Harmonics...... o .........-110 mc to 220 me
Radio Frequency Output. .... Lo coo.» . М excess of 100,000 microvolts
Modulation Frequency........ Pee we eae ...... Approximately 400 cycles
Audio Output......,......... Car 220.210 3 volts
Audio Frequency Input....... Cc ....... Approximately 5 у across 1 megohm
Tubes
12AU"....... La Done aaa 2. ..RF Oscillator-Buffer
6С4......... uns rss eee eae , «Audio Oscillator or Audio Amplifier
Power Requirements.......... penses ....105-125 v, 50/60 cycles
Cabinet Size......... o o 9 1/2 wide x 6 1/2 high x 5 deep
Shipping Weight......... meee eee mtn eee 7 lbs.
— “UU OL
~ UG ROY
HAND À
ВАНО Y
FAL II
— 00D ER
Les
—
BAHR D
SELENIUM
or Wai.
A
Gl
O
|
С
iz ||
AF CHOKE
AF OUT
>
AF Ш
Page 2
INTRODUCTION
The Heathkit model SG-8 Signal Generator has been designed for simplicity of construction and
Stability of operation. A litile care taken during the process of construction will reward the kit
builder with a signal generator which will give excellent performance and will be both pleasant
and easy to use. This generator has been engineered so that it will be valuable to the radio re-
pairman, ham and experimenter over a wide range of uses, in addition to being a rugged and
highly dependable piece of test equipment. К is made with high quality parts, conservatively
rated, and will give long andefficient service. The model SG-8 Signal Generator utilizes factory
adjusted coils, thereby eliminating the necessity of having costly equipment available to cali-
brate the finished kit.
CIRCUIT DESCRIPTION
The RF portion of the SG-8 Signal Generator consists of a 12AU7 twin triode tube. One triode
section of this tube is usedas a Colpitts oscillator. The other triode section is used in a cathode
follower type circuit and acts as a buffer between the oscillator and the output of the signal gen-
erator. Four inductances wound on forms comprise the coils for bands A, B, Cand D. Theyare
switched intothe circuit by means of the band switch. The E band coil is unique in its construc-
tion insofar that the heavy buswire of which it is composed actually forms the connections be-
tween the band switch and the tuning condenser for all of the lower frequency coils. When the
band switch is placed in E band position, a short is placed across the leads of the E band coils ,
thereby making it a closed circuit inductance which is capable of tuning from 25 to 100 mega-
cycles.
In a Colpitts oscillator circuit, feedback necessary to maintain oscillations is obtained from a
capacitive reactance divider across the inductance of the frequency determining circuit. In the
model SG-8, a capacitive divider is obtained by the use of a split-stator condenser. The ad-
vantage of this will be made apparent from the following explanation. For example, take a ca.
pacitive divider composed of fixed capacities. As the frequency across the condensers is in.
creased, the reactance of the condensers is decreased. Therefore, using a fixed capacitive
divider, as the frequency is increased reactance would become lower until a point was reached
where oscillations could no longer be maintained. By the use of a split-stator condenser for
both tuning and as the divider network as the frequency is increased, the capacity of the con-
denser dividing network is decreased. The reactance of a condenser for any given frequency is
inversely proportional tothe capacity. This tendsto maintain the reactance of the network fair-
ly constant, thereby permitting oscillation over a wide range of frequency.
The use of the cathode follower as a buffer stage has the following advantage: The characteris-
ties of a “cathode follower" are very low output impedance with an extremely high input imped-
ance, The extremely high input impedance produces little or no loading onthe oscillator circuit .
The very low output impedance provides a very stable output from the signal generator. The
effect is such that a varying load on the output of the signal generator will produce little or no
frequency instability of the oscillator. The signal generator incorporates a step attenuator for
coarse control of radio frequency output afid a continuously variable attenuation circuit for fine
control of the radio frequency output.
The audio oscillator is also a Colpitts circuit. By the use of the large inductance of an iron-
core choke and relatively high capacity in the capacitive divider, it is made to oscillate at ар-
proximately 400 cycles. This type of oscillator was again chosen for its stability and purity of
waveiorm. With the modulation switch in the INT. position, 400 cycles audio voltage is ap-
plied through a resistance network to the grid of the cathode follower stage. This audio voltage
iS impressed as an amplitude modulated signal upon the RF output from the cathode follower .
At the same time the audio voltage is also applied to the external audio connector marked OUT ,
and may be used as an audio signal source for testing amplifiers, etc. With the modulation
switch in the EXT, position, any external audio source of any frequency may be used to modu-
late the RF output of the signal generator. The 6C4 audio oscillator tube then becomes an am-
plifier stage for the external signal.
Page 3
The power supply consists of a transformer which furnishes filament voltage to the 6C4 and
12AU7 tubes, and effectively isolates the instrument from the AC line. A selenium rectifier is
connected to one winding of the transformer producing half-wave rectification. An RC filter
network changes the pulsed output from the rectifier to fairly pure DC. The 110 volt input has
both sides bypassed to minimize the Signal feeding back through the power lines.
A unique design feature is the convenient AF IN-OUT controi, which adjusts audio input if ex-
ternal modulation is employed and likewise adjusts the AF output level when using the generator
as a source of audio output.
PRELIMINARY INSTRUCTIONS AND NOTES
the Heathkit model SG-8 Signal Generator when constructed in accordance with the instructions
in this manual, is a high-quality piece of test equipment, capable of years of trouble-free sery-
ice, We therefore urge you to take the necessary time to assemble and wire the kit carefully .
You will be rewarded with a neat appearing, well-built and dependable test oscillator.
This manual is supplied to assist you in every way to complete the signal generator with the
least possible chance for error. We suggest that you take a few minutes now and read the en-
tire manual through before any work is begun. This will enable you to proceed with the work
much faster when construction is started. The large, fold-in pictorials are handy to attach to
the wall above your work space. Their use will greatly Simplify the construction of the kit.
These diagrams are repeated in smaller form within the manual. We suggest that you retain
the manual in your files for future reference, both in the use of the Signal generator and for its
maintenance,
UNPACK THE KIT CAREFULLY AND CHECK EACH PART AGAINST THE PARTS LIST. In
so doing, you will become acquainted with each part. Refer to the charts and other information
shown on the inside covers of the manual to help you identify any paris about which there may be
a question. [some shortage is found inchecking the parts, please notify us promptly and return
the inspection slip with your letter to us. Hardware items are counted by weight, and if a few
are missing, please obtain them locally if at all possible.
Read the note on soldering on the inside of the backcover. Crimp all leads lightly to the termi-
nal before soldering. Be sure both the lead and the terminal are free of wax, corrosion, or
other foreign substances. Use only the best rosin core solder, preferably a type containing the
new activated fluxes, such as Kester "Resin-Five," Ersin "Multicore," or similar types.
NOT REPAIR OR SERVICE |
INSTRUMENTS IN WHICH ACID CORE SOLDER OR PASTE FLUXES HAVE BEEN |
| USED. WHEN IN DOUBT ABOUT SOLDER, IT IS RECOMMENDED THAT A NEW |
|| ROLL PLAINLY MARKED "ROSIN CORE RADIO SOLDER” BE PURCHASED.
the parts list, Therefore a 100 KQ resistor may test anywhere from 80 КО to120KQ. (The let-
ter K is commonly used to designate a multiplier of 1000.) Tolerances on condensers are wen-
erally even greater. Limits of +100% and -50% are common for electrolytic condensers. The
parts furnished with your Heathkit have been specified so they may not adversely affect the Op-
eration of the finished signal generator.
In order to expedite delivery to you, we are occasionally forced to make minor substitutions of
parts. Such substitutions are carefully checked before they are approved, and the parts sup-
plied will work satisfactorily. By checking the parts list for resistors, for example, you may
find that a 2.2 megohm resistor has been supplied in place of a 2 megohm as shown in the parts
‚list, These changes are self-evident and are mentioned here only to prevent confusion in check-
ing the contents of your kit.
We strongly urge that you follow the wiring and parts layout shown in the manual. The position
Page 4
of wires and parts is extremely critical in circuits operating at high frequencies, and changes
may seriously affect the characteristics or calibration of the signal generator.
STEP-BY-STEP ASSEMBLY INSTRUCTIONS
The following instructions are presented in a simple, logical, step-by-step sequence to enable
you to complete your kit with the least possible confusion.
Be sure to read each step all the way through before starting. When a step is completed, check
it off in the space provided. This makes it easy to resume construction after your work has
been interrupted.
Leads on condensers, transformers, and resistors are generally much longer than they need
be to make the indicated connections. In these cases, the excess leads shouid be cut off as the
parts are added to the chassis. Not only does this make the wiring much neater but in radio
frequency work, the excess length of leads may actually create tuned parasitic circuits at un-
desired frequencies.
NOTE: We suggest that you execute the following preparations before any work is started:
1. Select from the large fold-in pictorials included with the manual the diagram showing the
phase of construction you are engaged in at thetime. Attach this diagram to the wall above
your work space. |
2. After identifying the parts from the parts list, lay them out in a large shallow box so that
they are readily accessible. This will save considerable time in construction.
3. Read thoroughly the assembly and wiring instructions on the inside rear cover of the manual
and refer tothe general information on both inside covers of the manual to identify the parts.
NOTE: In assembling the kit, use lockwashers under all nuts unless a solder lug is used. The
3-48 screws and nuts used in mounting the miniature tube sockets are the only exception to this
rule,
Unless otherwise stated, 6-32 screws, iockwashers and nuts are used in mounting of parts.
Wire is to be insulated unless otherwise specified. Insulated sleeving is to be used on bare
wires when called for.
ASSEMBLY OF SUB-CHAESIS
"El
E
a AE FE
G =
Figure 2
Расе 5
( /) Mount two 6-32 spade bolts onthe sub-chas- os
515 aprons as shown in Figure 2. Method of
mounting is shown in Figure 3.
(М) Mount a 9-pin miniature socket R on the sub-
chassis, using 3-48 screws and nuts. Posi-
tion as shown in Figures 1 and 2.
| Fipure 3
(=) Mount the tuning condenser as shown in Figures1 and 4, using 3/16 6-32 screws with lock-
washers under the heads.
r
(/) Mount the band switch В, using a control lockwasher and control nut. Omit-the flat washer.
Position as shown in Figure 2. See Figure Y for method of mounting controls.
@
©
N Figure 4
Cy ) Referring to Figure 4 for coil identification, and Figure 1 for coil position, mount the coils |
A, В, С and D. Referring to Figure 2, note that coil С has a 3-lug terminal strip mounted
eT pane on its lower mounting screw, and coil A has
кн " a solder lug on its upper mounting screw.
como caps | Use lockwashers on all coil mounting screws
€. (3) y ml \ except the one having the solder lug.
© mS
( ) Mount a cable clamp on the bottom mounting
I screw of coil A as shown in Figure 2, using
HOW TO MOUNT CONTROLS в SMITCHES an additional 6-32 nut to secure it.
Figure 5 WIRING THE SUB-CHASSIS
NOTE: Before beginning the wiring, refer again to the notes on wiring and soldering on the in-
side rear cover of the manual. We cannot stress too strongly the importance of careful wiring
and soldering when applied to radio frequency circuits. In building this signal generator you
will use a considerable amount of bare wire. Care should be taken to avoid possible shorts to
the chassis or other components. The leads should be kept short and straight when possible.
soidering should be done with a great deal of care, so that fluxes will not run over onto adjacent
insulation, thus causing leakage and a possible source of trouble.
Components are given code designations so that the identification of parts on both the diagrams
and on written matter is easily defined. The switch terminals are numbered in such a manner
that if the switch were viewed from thefront, the numbering system would progress in a clock-
wise direction around the switch. The band switch sections arereferred to as BF or BR, corre-
sponding to the front and rear sections of the switch when viewed from the shaft end. The tube
sockets are also numbered in a clockwise direction, as viewed from the bottom, starting from
the gap between the socket terminals. Thus a reference to R4 refers to the number 4 terminal
- On socket В, counted from the first terminal to the left of the open Space between terminals 1
and Y on that particular socket. In wiring the sub-chassis, reference to Pictorials 1 and 2 will
illustrate the placement of all parts and leads.
Page 6
` TO PILOT LIGHT
PICTORIAL 2
PICTORIAL 1
Page 7
(S) means solder. (NS) means do not solder yet.
(\/) Co meet a 33 КЯ resistor from TA1 (NS) to ТА? (NS).
(Y) Connect a 470 KQ resistor from TA2 (NS) to R2 (NS).
(Vv) Connect a 150 uuf ceramic condenser from ТА? (NS) to R2 (NS).
(4) Connect a 10 puf ceramic condenser from R2 (S) to R6 (NS).
(1) Connect a 1 КЯ resistor from R3 ($) to ТАЗ (NS).
(/ } Connect a 6" length of wire to ТАЗ ($). Leave the other end free.
e
(/) Connect а 100 КО resistor from ТА? ($) (use sleeving) to the solder lug (NS).
( A Connect a wire about 9" 1опе to TA1 (S). Run wire as shown in Pictorial 2 through the cable
clamp. Leave the other end free.
:
Е
( Л Connect а wire about 9" long to В4 (NS). Run wire аз shownthrough thecableclamp. Leave
the other end free. |
d ) Connect a short bare wire from R4 (S) to RS (NS).
( 4 Connect a wire about 4" long to R5 (S). Leave the other end free.
( J Connect a bare wire from R6 {S) to CC2 ($).
(7) Connect a 33 uuf ceramic condenser from CC1 (S) to R7 (NS).
( À Connect а 15 KQ resistor from R7 (5) to the solder lug (NS).
(./) Connect a short bare wire from R8 (S} to the solder lug (NS).
(Y) Connect a short bare wire from R9 ($) to the solder lug ($).
( Connect a bare wire to В1 (3). Cover with a 2 1/2" length of sleeving. Run wire through
hole S to CI (NS).
(A Connect a piece of bare wire 7 1/2" long to Al (S). Slip a 1 7/16" length of sleeving over
this wire and run through Bl ($), add a 4 1/2" length of sleeving and run through € 1(S), add
a 1 1/8" length of sleeving and connect to Di (NS).
A Connect a short bare wire from BR12 on the band switch (S) to BF12 (S}.
( 4 Connect a bare wire from ВЕТ (S) to A2 (5).
(.) Connect a bare wire from BF2 (S) to B2 (8).
(Y) Connect a bare wire from BF3 (8) to C2 ($).
ch Connect a bare wire from BF4 (5) to D2 (8).
| КА Connect a bare wire from BRI {8) to АЗ (8).
( /) Connect а bare wire from BR2 (5) to B3 (5).
Page $
{ „3 Connect a bare wire from BR3 {S) to C3 ($).
(Y) Connect a bare wire from BRé (S) to D3 (8).
(7) Connect coil E3 from ВЕБ ($) to BR5 (S).
(4) Cover one bare lead from coil E3 with a 3 1/2" length of sleeving, and connect to Dl (3).
Leave the other end free,
(Y) Connect coil El from BF6 (8) to ССЗ ($).
=
(SÍ) Connect coil E2 from BR6 (5) to CCA (S).
This completes the sub-chassis wiring.
ASSEMBLY OF CHASSIS
NOTE: Refer to Figure 6. Figure 6
(Y Install 3/8 rubber grommets in holes A. C, D, Е Fand P.
u Mount a 7-pin miniature socket in hole G, using 3-48 screws and nuts, Position as shown
in Figure 6.
(Y) Mount the selenium rectifier with the side having the plus or cathode marking facing out.
ward from the back of the chassis. Use a i'' 6-32 screw through the dimpled hole in the
rear apron of the chassis. Fasten with a tockwasher and nut. Position as shown in Figure
G.
Page 9
(J) Mountthe audio choke on top of the chassis to the rear of the tube socket. Use 3/8 6-32
screws, placing a solder lug under the nut nearest the tube socket and the lockwasher under
the other nut. Position the solder lug as shown in Figure 6.
E
(4) Mount the power transformer on top of the chassis opposite the audio choke. Position the
transformer in such a manner that the red and yellow leads pass through the grommet near -
est the chassis edge.
(} On the back mounting screw of the transformer, place a solder lug on the under side of the
chassis. Position as shown in Figure 6.
( ) On the front mounting screw, mount a 2-lug terminal strip TC. Position as shown in Figure
6. Use a lockwasher under the nut. |
(4 Using 3/8 6-32 screws, mount a solder lug at hole H and a 3-lug terminal strip TB at hole
J, using a lockwasher on the latter. Position as shown in Figure 6.
A Mount the sub-chassis to the chassis by inserting the sub-chassis spade boits through the
small holes on either side of the large chassis cutout. Care must be taken to prevent dam-
age to the E band coils at this time. Lower the sub-chassis through the hole at a slight
angle to clear the E band coiis, and at the same time permit the band switch shaft to drop
down into the slotted hole in the front of the chassis.
|
a ry
7
O-
SOCKET
YELLOW
20-20
a MED
I30%Y
ote
PICTORIAL 3
Page 10
,
(./) Referring to Pictorial 3, place а solder lug on the right hand spade bolt as viewed from the
bottom, add a 6-32 nut and tighten.
( /) On the left hand spade bolt, place a 2-lue terminal Strip TD, a lockwasher and nut. Posi-
tion as shown in Pictorial 3.
(A solder a 1 3/4" length of shield braid directly on the chassis and sub-chassis as shown in
Pictorial 3.
{ A Mount the pilot light in the upper right panel hole, as viewed from the front. See Figure 7
for method of mounting,
{ A Mount the three shielded connectors in the holes marked AF IN, AF OUT, and RF OUT.
See Figure 8 for method of mounting.
NOTE: The controls are mounted through both the chassis and panel and hold the panel to the
chassis. Refer to Figure 5 for method of mounting controls, The controls are lettered the
Same as the hole markings on Figure 6.
( у Mount the two position EXT-INT modulation switch in ное К. Position terminals as shown
in Pictorial 3.
( “4 Mount the 1 megohm potentiometer L in hole L, and position terminals as shown in Picto-
rial 3.
( À Mount the 1 KQ control M in hole M, and position terminals as shown in Pictorial 3.
v2 Mount the three position attenuator switch N in hole N, and position terminals as shown in
Pictorial 3.
гс
À GR ÜLEH D
Figure 7 Figure 8
WIRING OF CHASSIS
NOTE: Exercise care when wiring chassis to avoid damage to E band coils.
(“ } Twist the two black wires from the power transformer together and connect either wire to
TB3 {NS).
(4 Connect the other black wire to TB1 (NS).
© Connect a .01 ufd ceramic condenser from TB3 (NS) to the solder lug on the opposite side
of hole F (NS).
(A Connect a ‚Ol 44 ceramic condenser from ТВ? (NS) to the same solder lug (S).
(A Connect either red wire from the transformer to the negative selenium rectifier terminal.
(The terminal nearest the chassis. ) (S).
Page 11
(у) Connect the other red wire to the solder lug directly below the rectifier (NS).
(vJ Connect elther yellow wire from the transformer to this solder lug (NS).
(A Run the other yellow lead as shown in Pictorial 3, through the grommet P. Leave the other
end free.
(Y) The 20-20 uid 150 volt filter condenser has two leads on the end marked "positive," and
one lead on the other end. The condenser is mounted between the solder lug and the ter-
minal strip TC as shown in Pictorial 3.
(+9 Connect the single negative wire to the solder lug (S).
( À Connect the two positive wires of the condenser to TC1 and TC? (NS).
(“) Connect а wire from the positive rectifier terminal (S} to TC2 (NS).
(v) Connect a 3.3 KQ 1 watt resistor from TC? (S) to TC1 (NS).
( À Connect a .005 ufd disc ceramic condenser from TC1 (NS) to the adjacent solder lug (NS).
(LY Twist two wires about 10" long together. Connect one pair of wire ends to the two switch
terminals on the back of control M (S).
(—) Run the wires as shown in Pictorial 3 to the terminal strip TB. Connect one wire to ТВ!
(S).
Page 12
(/) Connect the other wire to TB2 (NS).
(J Connect a bare wire to М1 (S). Run the wire through N11 (NS) to the solder lug adjacent to
the large panel cutout (S).
(v} Connect a 47 © resistor from N11 (NS) to № (NS).
(+) Connect a 47 Я resistor from Nil ($) to № (NS).
(+9) Connect a 680 2 resistor from N3 (S) to № (NS).
(14 Connect a 680 © resistor from N5 (S) to NT (NS).
(7) Connect a bare wire toN7(S). Cover with al 1/2" length of spaghetti and connect to M2 (3).
(I Connect the free end of the wire coming from TA3 (see Pictorial 2) to M3(S). Run wire as
shown in Pictorial 3.
(3 Connect a bare wire to № (S). Cover wire with a 2 1/2" length of spaghetti. Run wire
through grommet P and connect to the center terminal of the RF OUT connection (S). See
Pictorial 4,
(A Connect a short bare wire from the lug on the RF OUT connector (8) to the pilot light ter-
minal nearest the panel ($).
vA Connect the free end of the yellow transformer wire to the rear pilot light terminal (NS).
(+) Connect the free end of the wire coming from R5 (see Pictorial 2) to the same pilot light
terminal (8).
(Y Connect the remaining bare wire of coil E3 to TC1 (NS). (Use sleeving. )
(4 Connect a wire to ТС1 ($}. Run wire along rear of chassis as shown in Pictorial 3, to ТО
(NS).
(.) Connect a short bare wire from G1 (S) to K12 (S).
(„I Connect the free end of the wire coming from R4 (see Pictorial 2) to СЗ (8).
( -) Connect the free end of the wire coming from TAI (see Pictorial 2) to TD2 (NS).
(4 Connect a short bare wire from G4 (5) to the solder lug adjacent to the tube socket (NS).
(A Connect a .01 wid ceramic condenser from G5 (NS) to TD2 (S).
(A) Connect a 5600 & resistor from G5 ($) to TDI (3).
(x) Connect a 100 KQ resistor from G6 (NS) to the solder lug (NS).
(„) Connect a .01 uid ceramic condenser from G6 (S) to K2 ($). (Use sleeving. )
(4) Connect a 330 Q resistor from G7 (S) to the solder lug (NS).
() Connect а 390 КО resistor from K8 (NS) to K10 (S)..
( Y Slip a 7/8" length of spaghetti over each lead of the .01 ufd ceramic condenser, and connect
the condenser from K8 (5) to L3 (NS).
Page 13
( A Connect a wire to LS (8). Run the wire through the grommet A to the center terminal of the
AF IN connector (3). See Pictorial 4.
(x) Connect either lead from the audio choke to K11 (NS).
NS Connect the outside foil lead of a .1 ufd condenser to the solder lug (NS),
ce Connect the other lead of this condenser to K11 (S). Position condenser as shown in Picto-
rial 3,
(+) Slip a 3/4" length of sleeving over each lead of a .01 Ша ceramic condenser. Connect one
lead of the condenser to Ki ($5). Connect the other lead to L2 (NS).
( va Connect a wire to L2(S). Run the wire through the grommet А to the center terminal of the
AF OUT connector (3).
(у Connect a wire from Ll (S) to the solder lug (NS). See Pictorial 3.
г
Y Connect the remaining lead from the audio choke to K3 (NS).
A
) Cut the lead opposite the outside foil end of a .02 ша condenser to 3/4" in length. Connect
this lead to КЗ {$}.
(.Х Connect the outside foil lead of this condenser to the solider lug ($).
(У Insert the line cord through the grommet Е in the rear of the chassis. Tie a knot in the
cord about 1 1/2” from the end. Connect one lead to ТВ? ($).
.
{ Connect the other lead to TBS ($).
4 Mount pointer knobs on the five controls at
the bottom of the panel. If the pointers do
not line up properly with the markings on
the panel, remove the knob, loosen the con-
. troi nut and turn the control slightly until
Figure 9 they do line up.
(À See Figure 9 for details of mounting the tun-
ing controls. The pointer should be adjusted
to cover the entire scale whenthe condenser
is rotated.
b
iA) Install the 12AU7 tube in the 9-pin socket on the sub-chassis.
| Figure 10
(A Install the 6C4 tube in the 7-pin socket on the chassis.
( y Assemble the handle to the cabinet using two 10x24 screws.
y Ä n Fi
( ) Instali the rubber feet on the cabinet as shown in Figure 10. INSTALL FEET
i | HOWN
A Slide the chassis into the cabinet with the line cord through AS SHO
the hole in the back of the cabinet. = (|
“4 Y) Fasten the unit to the cabinet with two #6 sheet metal screws
through the back of the cabinet.
This completes the assembly and wiring of your Heathkit model SG-8 Signal Generator.
Page 14
TEST LEAD ASSEMBLY
|
>
| À .
— т re =. =. — = o a в. L
Figure 11
The test lead is assembled as shown in Figure 11. One end of the shielded cable is connected to
the shielded plug; the other end has alligator clips mounted on it for connection to the equipment
under test. First, remove the spring cable guard from the connector plug by loosening the
screw in the side of the plug. Slide this spring over the shielded cable, with the small end of
the spring toward the end that is tobe connected tothe plug. The outside insulation onthe cable
is then cut back for a length of about 3/4", then flare the shield braiding at the end of the cable
so that it may be pushed back over the small end of the spring cable guard. The inner connector
is then stripped for a length of approximately1/8". The assembly at this point is slid back into
the connector so that the inner coaxial wire passes through the rivet in the insulated end of the
connector, the cable guard with the shielded braid flared over the end is pushed back into the
connector and the screw tightened to hold it in place. Solder the inner connector.
Slab lever nag isa
Th
ег cul oy
F
Send sharply and
ит a чение яме инь
= АНИ WUT ГЕ e
driver or knife
nlade. Pull in-
shielden test Ted eds
Wir ranpeniar.
тет ice oul ob
Shia ld jeg.
Figure 12
METHOD OF PREPARING SHIFLDET [- Ab
27
thy”
IÓ
ме By
--
On the other end of the shield cable, the outer insulation is cut back about 4'' and the cable pre-
pared as shown in Figure 12. Solder alligator clips to both the inner conductor and the shield
braid.
ACCURACY
Any signal generator is designed as a convenient andcontrollable source of modulated or unmod..
uiated signals. No signal generator is designed as a irequency standard. Expensive standard
signal generators have fairly accurate (3 to 20%) attenuators which control the output voltage
‚ and the calibration accuracy is rarely closer than 1%. The Heathkit signal Generator may be
expected to fail within 2 to 3% of the frequency calibration, which is quite satisfactory for ser-
vice work and alignment. In receiver adjustment, the frequency at which the particular adjust-
ment 15 made is rarely critical but the adjustment itself for maximum signal output from the
Page 15
receiver is frequently quite critical. For accurate calibration of home built receivers or equip-
ment, proceed as follows. Make a rough calibration with the signal generator. Then, with a
receiver, tune in WWY (Bureau ol Standards) at 2.5, 5, or 10 mc. Set the signal generator toa
suitable sub-harmonie, such as 300 or 1000 kc, and adjust the generator for zero beat. Now
harmonics of the signal generator occur every 000 ke or 1 megacycie, and these harmonics may
be used to give accurate calibrations at points 500 or 1000 ke apart, such as 2900 ke, 3000 kc,
9000 ke, 4000 kc, etc. These known frequency points can be marked on the dialof the equipment
being calibrated. The object of the rough calibration is merely tofurnish a means of identifying
for example, the 3000 ke point from the 2000 ke or 3500 ke points. For calibration of higher
irequency equipment, a choice of higher sub-harmonic wiil reduce the confusion between the
muilitude of harmonics and will also insure adequate signal strength. When checking the cali-
bration accuracy of the Heathkit Signal Generator, the most convenient standards of comparison
of sufficient accuracy are broadcast stations of known frequency. Crystal oscillators of standard
frequency when zero beat against WWV, are also convenient to use if available. The use ol re-
ceiver dial calibrations is frequently not of sufficient accuracy to warrant consideration. |
USE OF THE ВЕ SIGNAL GENERATOR
This signal generator can be used to align radio receivers. It furnishes a source of radio Íre-
quency or modulated radio frequency by means of signal generator fundamental frequencies be-
tween 160 ke and 100 megacycles (1 megacycle equals 1000 kilocycles) and useful harmonics of
the signal generator may be used to over 200 megacycles.
Wherever possible, the recommendations of the manufacturer of the radio being aligned should
be used. When this information is not available, the following procedure can be used.
Output Indications: With the new types of receivers, especially those using AVC (automatic vol-
ume control}a visual means of indicating resonance is desirable. If convenient, in all receiver
alignments the AVC should be disabled during the process of alignment, otherwise the output of
the signal generator should be sufficiently attenuated to prevent AVC operation in the receiver.
IF Alignment: Connect the signal generator shield to chassis (ground clip). Clip the hot lead
from the signal generator to the control grid terminal on the converter or mixer tube socket.
Set the signal generator to the IF frequency required. RMA standard is 495 ke but other Ire-
quencies like 262 and 175 Кс are sometimes used. Adjust the generator output for a minimum
readable output indication. Adjust IF transformers starting with the one nearest the second de-
tector and working forward. The adjustment mechanism consists generally of two screws which
operate trimmer condensers or iron cores inside the coils. They may be located on top, on the
side, or on the top and bottom of the IF transformer, Turn the adjusting screw for maximum
output, reducing the signal generator output if necessary to keep the output indicator from going
off scale.
Oscillator Alignment: With the generator connected as above, set the generator dial to the high-
est frequency marked on the receiver dial. (1600 or1720kc.) Set the receiver dial to this same
frequency. Adjust the receiver oscillator trimmer to bring in the signal, An additionai adjust-
ment is often provided in the form of a padding condenser or iron core. This is generally ad-
justed at 600 ke and its final adjustment is made later.
ВЕ Alienment: Using a 200 uuf condenser between generator and antenna post, set receiver
and generator to 1400 Кс, Adjust antenna and RF trimmer (if used), (frequently located on the
tuning condenser) for maximum output. Set generator to 600 ke and "rock" tuning condenser
through the signal while adjusting the oscillator padder for maximum output at resonance.
For receivers with a loop antenna, couple the signal through a single turn loop connected to the
‘generator output. Tuned radio frequency receivers are aligned as shown under "RF Alignment,”
The AF output source can be used to test audio amplifiers. To make such tests, connect the
test lead tothe AF OUT jack and throw the modulation switch to INT position. Connect the alli-
gator clip on the ground lead from the generator to the chassis of the amplifier under test. The
Page 16
alligator clip on the hot lead from the generator is then touched to the grid (through a .05 ufd
condenser) of the audio Stage under test, This should produce an audible output of approximately
400 cycles if the stage is operating correctly and is connected to a good speaker.
Output Voltage: The RF signal strength going into the output control depends upon the strength
of oscillation of the 12AU7 oscillator. In all variable frequency oscillators the amplitude will
vary with the tuning condenser setting. With careful design the variation may be minimized.
In the Heathkit Signal Generator, the variation is kept down to a ratio of about 2 1 /2 to Lon each
band except band E, where the L/C (inductance to capacitance) ratio becomes sufficiently un-
favorable that oscillation may drop off rapidly in strength when the condenser is near maxi-
mum Capacity. However, even on this band, the output of the SG-8 is in excess of 100,000 mi-
prove’ which is more than sufficient for the average application in which this generator will
e used. |
IN CASE OF DIFFICULTY
I, Recheck the entire wiring. Follow each lead and color it on the pictorial with a colored
pencil, H possible, have a friend recheck the wiring for you. Most cases of difficulty re-
sult from wrong or reversed connections. In this unit, there is alsothe possibility of shorts
to the chassis occurring on some of the bare wire connections from the coils. These wires
should be carefully spaced away from the chassis when the instrument is assembled.
2. Check the test lead with an ohmmeter to be sure there are no shorts between the inner and
cuter conductor caused by overheating during the soldering process.
3. If the wiringis found tobe correct and the signal generator still refuses to work, try chang-
ing tubes. It 1$ possible that one of the tubes is defective.
4. Check the voltages. A voltage chart is included showing the normal voltage to be expected
at the pins of the tube sockets. These voltages were measured with an 11 megohm input
vacuum tube voltmeter. A normal variation of +15% is to be expected. With regular volt-
meters, readings may be very much lower. All voltages are DC unless otherwise indicated.
о. If only one band onthe signal generator is inoperative, it is very likely that the coil associ-
ated with that band has become damaged. Anohmmeter connected between the terminals of
the coil should show continuity. If it does not, one section of the winding is open.
VOLTAGE CHART
TUBE Pint | Pin2 | Pin3 | Pina | Pind | Ping | Pin? | Pins | Ping
6C4 65 NC |63 АС; 0 65 | -6.5
. | A _ +—— —
L2AU7 || 65 -2 2.5 | 6.3 АС | 6.3 АС | 85 *3to-30 0 | 0
*Dependent upon band.
NC - No connection.
Page 17
o eee ee ee nn nn ини ee
REPLACEMENTS
Material supplied with Heathkits has been carefully selected to meet design requirements and
ordinarily will fulfill its function without difficulty. Occasionally improper instrument opera-
tion can be traced to a faulty tube or component. Should inspection reveal the necessity for re-
piacement, write to the Heath Company and supply all of the following information:
A. Thoroughly identify the part in question by using the part number and description found in
the manual parts List.
B. Identity the type and model number of kit in which ii is used.
C. Mention the order number and date of purchase.
D. Describe the nature of defect or reason for requesting repiacement,
The Heath Company will promptly supply the necessary replacement. Please do not return the
original component until specifically requested to do so. Do not dismantle the component in
question as this will void the guarantee. If tubes are to be returned, pack them carefully to
prevent breakage in shipment as broken tubes are not eligible for replacement. This replace-
ment policy does not cover the free replacement of parts that may have been broken or damaged
through carelessness on the part of the kit builder.
SERVICE
In event continued operational difficulties of the completed instrument are experienced, the fa-
cilities of the Heath Company Service Department are at your disposal. Your instrument may
be returned for inspection and repair for a service charge of $3.00 plus the cost of any addi-
tional material that may be required. THIS SERVICE POLICY APPLIES ONLY TO COM-
PLETED INSTRUMENTS CONSTRUCTED IN ACCORDANCE WITH THE INSTRUCTIONS AS
STATED IN THE MANUAL. Instruments that are not entirely completed or instruments that
are modified in design will not be accepted for repair. Instruments showing evidence of acid
core solder or paste tluxes will be returned not repaired.
The Heath Company is willing to offer its full cooperation to assist you in obtaining the proper
Operation of your instrument and therefore this factory repair service is available for a period
of One year from the date of purchase.
SHIPPING INSTRUCTIONS
Before returning a unit for service, be sure that all parts are securely mounted. Attach a tag
to the instrument giving name, address and trouble experienced. Pack in a rugged container,
preterably wood, using at least three inches oí shredded newspaper or excelsior on ail sides.
DO NOT SHIP IN THE ORIGINAL KIT CARTON AS THIS CARTON IS NOT CONSIDERED
ADEQUATE FOR SAFE SHIPMENT OF THE COMPLETED INSTRUMENT. Ship by prepaid
express if possible. Return shipment will be made by express collect. Note that a carrier
cannot be heid liable for damage in transit ii packing, in HIS OPINION, is insufficient.
SPECIFICATIONS
All prices are subject to change without notice. The Heath Company reserves the right to dis-
continue instruments and to change specifications at any time without incurring any obligation
to incorporate new features in instruments previously sold.
WARRANTY
The Heath Company limits its warranty of paits supplied with any kit (except tubes, meters and
rectifiers, where the original manufacturer's guarantee only applies) to a period of three (3}
months from the date of purchase. Replacement will be made only when said part is returned
postpaid, with prior permission and in the Judgment of the Heath Company was defective at the
time ol sale. This warranty does not extend to any Heathkits which have been subjected to mis-
use, neglect, accident and improper installation or applications. Material supplied with a kit
Shall not be considered as defective, even though not in exact accordance with specifications, if
"it substantially fulfills performance requirements. This warranty is not transferable and ap-
plies only to the original purchaser. This warranty is in lieu of ail other warranties and the
Heath Company neither assumes nor authorizes any other person to assume for them any other
liability in connection with the sale of Heathkits.
Page 18
sos MES NN EEE ee USE
The assembler is urged to follow the instructions exactly as provided. The Heath Company
assumes no responsibility for the operation of the completed instrument, nor Liability for any
damages or injuries sustained in the assembly or operation of the device.
HEATH COMPANY
Benton Harbor, Michigan
Page 19
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Page 20
DESCRIPTION
Indicator assembly
Shielded connector
7-pin miniature socket
9-pin miniature socket
Pilot light nut
Piiot light jewel
Pilot light socket
Pilot light bushing
Knob
Pointer knob
3-48 x 1/4 screw
6-32 x 3/16 screw
#6 x 3/8 sheet metal screw
6-32 x 3/8 screw
6-32 x Е screw
8.32 x 1/8 set screw
10-24 x 3/8 handle screw
Set screw
6-32 spade bolt
3-46 nut
6-32 nut
Control nut
Control nickel washer
3/4 flat washer
#6 lockwasher
Control lockwasner
#6 Solder iug
Line cord
1/8" cable clamp
Alligator clip
length #20 bare wire
length Shielded test lead
roll Hookup wire
length Shield braid
length Spaghetti |
Shielded plug
Chassis-Panel- Manual
Cabinet
Chassis
Sub-chassis
Panel
Handle
Instruction Manual
PARTS LIST
PART PARTE DESCRIPTION PART PARTS
No. Per Kit No. Per Kit
Resistors Sockets-Knobs-Jacks
1-1 2 47 2 100-M10 1
1-4 1 330 £ 432.3 3
1-7 2 680 2 434-15 1
1-9 1 1 Kg 434-16 1
1-3A 1 3.3 KQ 1 watt 252-12 1
1-18 1 5600 £ 413-1 1
1-21 1 15 КО 434-22 1
1-24 1 33 КО 455-1 1
1-26 2 100 K& 462-6 1
1-32 1 390 ES 462-M11 5
1-33 1 470 KR
Condensers Hardware
21-3 1 10 вы 200-2 4
21-7 1 33 Lu 250-7 3
21-11 ] 150 ци 250-8 2
21-15 6 OL pid 250-9 8
21-27 1 ‚005 wid 250-13 1
23-8 1 ‚02 ufd 250-15 1
23-11 1 .1 pfd 250-19 2
25-7 1 20-20 ufd 150 y 250.22 5
26-17 1 450 пы! dual tuning 251-1 2
252-1 4
Controls-Switches 252-3 20
10-32 1 1 megohm control 292-7 5
19-18 1 1 KR control with switch 293-10 4
63-67 1 5 position band switch 253-20 3
63-69 i 2 position modulation switch 2024-1 17
63-70 1 3 position attenuator switch 294-4 y
259-1 5
Coils-Chokes-Transformers
40-47A 1 Oscillator coil band A Clips-Plugs-Wire
49-476 H Oscillator coil band B 89-1 1
40-47С 1 Oscillator coil band С 207-3 1
40-470 1 Oscillator coil band D 260-1 2
40-47E 1 Oscillator coil band Е 340-2 1
46-1 1 AF choke 343-1 1
54-2 1 Power transformer 344.1 1
345-1 1
Tubes-Lamps-Rettifiers 346-1 1
57-2 1 Selenium rectifier 432-] 1
411-4 || 6C4 tube
411-25 1 12AU7 tube
412-1 1 #47 pilot light 90-14 i
200-M54 1
Grommets-Feet-Terminal Strips 200-M55 1
73-1 6 3/8 grommet 203-26F67 1
261-1 4 Rubber feet 211-1 1
: 431-2 2 2-lug terminal strip 595-713 1
431-3 2 3-lug terminal strip