DYNACO Stereo 70 Assembly instructions

SERIAL NUMBER
6701028
This number must be men-
tioned in all communica-
tions concerning Dynakit.
INPUT
DYNAKIT STEREO 70
LEFT
OJ LEFT RIGHT
MONO I ~mQ
S TfREO •
PAT. NOS. 2815407 and 2815408
BLASE. RIGHT
1. H v... ~
PREAMP POWER
()'rNA COMPANY
P""ILA-,. 'A
MAor IN U. S A
('ltCUII_Y "AnNlEP
Price $1.00

Power Output
Frequency Response
Power Response
Inte rmodulation Distortion
Hum and Noise
Sensitivity
Output Impedances
Damping Factor
Minimum Channel Separation
Power Consumption
Preamp Provision
Tube Complement
Size
Weight
Finish
SPECIFICATIONS
35
watts continuous, 80 watts peak each channel
±.5 db from 10 cps to 40 kc
20 cps to 20 kc within 1db of 35 watts at less than 1% distortion
Less than 1% at 35 watts (normally about .5%). Less than .05% at 1watt
Inaudible;
better than 90 db below rated power
1.3 volts rms input for 35 watts out
4, 8, 16
ohms each channel
15
55 db
190 watts 50/60 cps
Two power takeoffs with independent heater windings to eliminate
interaction. Each 6.3 volts 1 amp, 350 volts dc 10 mao Dynakit pre-
amplifiers plug in directly without modification.
EL-34 (4), 7199 (2), GZ-34/5AR4, selenium rectifier.
13" by 9-1/2" by 6-1/2" high
32 pounds
Chassis and bottom plate bright nickel plated. Cover finished in
charcoal brown vinyl paint.

-l:! 6 '70 70~~
INSTRUCTIONS FOR ASSEMBLING THE DYNAKIT STEREO 70
DESCRIPTION
Your Dynakit stereo 70 is a complete dual 35
watt power amplifier kit which offers the highest
possible fidelity, at low cost and in a compact
arrangement. It uses a patented circuit of out-
standing performance characteristics, along with
top quality parts, including the new Dynaco Super-
Fidelity A-470 transformers --the finest available.
The measured specifications show that the stereo
70 is an amplifier of unequalled performance, and
its lis ten in g quality is also unrivalled by any
regardless of price.
This amplifier has characteristics and power
rating ideal for either stereophonic or monophonic
use. The two non-interacting 35 watt channels
provide adequate power, in a stereophonic or two
channel system, for loudspeakers of any level of
efficiency. The channels can be paralleled for a
full 70 watts of low distortion output, suitable for
practically any monophonic use even where
several loudspeakers are in use in different areas.
The high power capability and low internal imped-
ance provide excellent damping for all types of
high
quality speaker systems without need to make
adjustments to match specific speaker installations.
The design features of your Dynakit which con-
tribute to its superior listening quality include some
which are not revealed by the customary steady-
state laboratory measurements. For example, the
stereo 70 does not exhibit bounce and flutter when
pulsed with a transient signal. Thus a sharp per-
cussive signal like a drum beat or a piano note will
be reproduced with sharpness and clarity and neit~er
overhang nor muddiness. The Stereo 70, unhke
many other amplifier circuits, has been designed to
provide its specified performance on a loudspeaker
load, not just under laboratory measuring condi-
tions. Therefore, the connection of a loudspeaker
to the amplifier does not deteriorate its perform-
ance or listening quality. In addition, due to the
high quality of the output transformers used, the
Dynakit's power handling capabilities are maintain-
ed over the entire audio band without the sharp rise
in distortion which characterizes most amplifiers
at the extremes of high and low frequencies.
The Stereo 70 uses a circuit arrangement based
on that of the Dynakits Mark n and Mark III which
has become world famous as one of superior qual-
ity while essentially simple and trouble -free. The
new 7199 tube is used as a pentode high gain voltage
amplifier directly coupled to a cathodyne phase
inverter. All parameters are adjusted for minimum
distortion. This type of phase inverter has the
unique advantage that its operation is independent
of tube aging so that no adjustments are required
in maintaining optimum performance.
An internal capacitive feedback loop balances
the phase inverter at the highest frequencies, and
the a r ran gem e n t provides accurately balanced
driving signals to the output tubes. These tubes
are type EL-34's (one pair for each channel) oper-
ating well below their maximum ratings. The out-
put tubes use a fixed bias arrangement which is
set through use of Dyna Biaset (pat pending) which
provides optimum linearity of the tubes and mini-
mizes the effects of unbalanced components. The
connection of the output tubes includes a small
percentage of screen loading which improves the
regulation of the output stage and makes it corr--
paratively uncritical of load impedance.
The imp e dan c e match and bias conditions
utilized in the output stage provide minimum dis-
tortion over a very wide dynamic range. In addi-
tion, 20 db of negative voltage feedback lowers the
distortion to an unmeasurable proportion at normal
listening levels and to less than 1% intermodulation
distortion at 35 watts output on each channel.
The use of a minimum number of phase-
shifting stages along with car e f u I transformer
design makes it practical to have unconditional
stability at both high and low frequencies. This
feature of the design means that there is no tend-
ency toward motorboating or oscillation under any
condition of use.
The inherent lin e a I' it Y of the circuit, the
complete stability, and the prefabrication of all
critical wiring on the printed circuit assembly
make construction completely non-critical. The
use of conservatively 0 per ate d, highest quality
components insures superior and de pendab I e
operation over along period of time.
GENERAL WIRING PRACTICE
Assembly of the Dynakit stereo 70 is quite
simple compared to general kit assembly require-
ments. This is true because all critical parts of
the Dynakit are factory assembled for you on the
printed circuit assembly. Other parts are put out
in
the open through a free and uncluttered layout
so there is easy accessibility for wiring or trouble
shooting purposes. Construction of your Dynakit
should not take more than about five hours because
of these simplifications.
Upon opening your kit, check the components
with the parts list. Familiarize yourself with the
components; they can be identified by comparison
with the pictorial diagram and by specified color
coding. Proper color coding will be mentioned for
each resistor as it is used.
Tools r e qui l' e d for easy assembly of your
Dynakit are soldering iron (small tip) or soldering
1

gun, long nose pliers, screwdriver, and wire
cutters. Although not essential, a low cost wire
stripper and cutter of the type which can be pur-
chased for less than $1.00 will greatly facilitate
cutting and stripping the various leads in the kit.
Good soldering technique is valuable in obtain-
ing sat i s f act 0 I' Y results from any electronic
equipment. ALL SOLDERING MUST BE DONE
WITH ROSIN CORE SOLDER.
There is no war-
ranty on any equipment in which acid core solder
has been used. Make sure that the solder used is
plainly marked "Rosin Core." If you have solder
on hand the origin of which is doubtful it is wise to
obtain new 50/50 or 60/40 l' a sin core solder.
Whenever sol del' in g is required, the assembly
instructions specify it by "(S)." If this symbol is
not shown aiter a connection is specified, it indi-
cates that further connections will be made at that
point before soldering.
Soldering is accomplished by heating the joint
with the iron until solder is hot enough to flow
when
touched to the joint. It is not desirable to
feed the solder to the iron. It should be fed to the
junction of iron and joint. After the solder flows,
the iron should be held in place for afew seconds
and removed when it is seen that the solder has
contacted both parts of the connection - the lug and
the wire to which it is connected. It should not
show a ball of solder but a smooth transition from
solder to component lead.
Before a p ply in g solder the joint should be
clean and the lead should be crimped in place so
as to have mechanical security. It is not neces-
sary to wrap leads around contacts many times. A
single turn and pinching together with long nose
pliers is suitable. After soldering, there should
be no play at the joint if the lead is wiggled with a
pair of plie rs. It is practical to do all soldering
with a pencil type iron of low wattage rating. A
small tip is extremely useful when working in a
confined space. If a solder ing gun is used, it
should be used with discretion since the amount of
heat available is far more than l' e qui red for
soldering light wires.
Component leads should be trimmed as they
are used; the length should be such that the proper
connection can be made from point to point without
strain on lugs or components. Care should be
exercised not to allow wires to touch one another
unless they are actually connected to the same
point.
The ins t I' Uc t ion swhich follow have been
arranged for simplified procedure in which the
work can be done without interference between the
various portions of the wiring. It is recommended
that the instructions be followed on a step by step
basis, checking off each stage as it is completed.
The pictorial diagrams should be used for refer-
2
ence and all connections checked against these
before going on to the next stage. If the wiring is
done methodically and each step checked carefully,
your amplifier should work without difficulty as
soon as it is completed.
MECHANICAL ASSEMBLY
PICTORIAL DIAGRAMS SHOULD BE CONSULTED
DURING
ALL PHASES OF ASSEMBLY
1("I) Mount
the seven octal sockets with 4/40
hardware (the smallest screws supplied).
Note that there is a small slot or keyway in
the center hole of each socket; be sure in
each instance that this keyway is properly
oriented as shown in the pictorial diagram.
Insert screws from the top of the chassis
and mount the sockets from the bottom.
Fasten with nuts and lockwashers.
2 (0 Place the bakelite insulator over the front
of the two socket input connector and mount
the combination from the inside of the
chassis using 4/40 hardware.
3 (II) Mount the SPDT slide switch (with three
lugs) next to the input connector. No nuts
or lockwashers are necessary since this
item has threaded holes.
4(.;) Mount the two four screw terminal strips
on the c has sis rear from the outside.
Fasten with 4/40 hardware.
5(v') Mount the two 10,000 ohm potentiometers
in the 3/8" holes near the center of the
chassis. Locate with the three connecting
lugs facing the front of th,: chassis. Put a
3/8" lockwasher on each shaft, insert from
the inside, and fasten with a 3/8" nut.
6 (0 Fasten the long 4/40 screw between the two
potentiometers with a 4/40 nut. Then place
the selenium rectifier over the screw. The
lug marked (+) should be closest to the
chassis and both lugs should face the rear
of the chassis. Fasten with 4/40 lock-
washer and nut.
7(J) Mount
the rubber grommet in the 3/8" hole
in
the cente l' of the rear fl a n g e of the
chassis.
8 (/). Mount the fuse post in the D shaped hole in
the rear of the chassis. The rubber washer
goes between the chassis outside and the
shoulder of the fuse post. Fa s ten with
special nut provided.

9(L1 Mount the SPST on-off switch (two lugs) on
the chassis rear. The con nee tin g lugs
should be located as shown in the pictorial
diagram. No lockwashers or nuts are
necessary.
WIRING PROCEDURE
EACH LENGTH OF HOOKUP WIRE SPECIFIED
SHOULD HAVE APPROXIMATELY 1/4" OF
INSULATION STRIPPED FROM EACH END
UNLESS OTHERWISE SP
ECIFIED.
13 (---) Mount both A-470 output transformers with
#8 hardware. Note that the shorter leads
come through the holes in the rear.
12 (-1 Us ing 4/40 hardware, mount the seven lug
terminal strip on the left side opposite the
choke, following the pos ition shown in the
pictorial diagram.
11 () Mount the choke, C-354, on the right side
below the c has sis. Put the #8 screws
through the chassis from the top and fasten
underneath with lockwashers and nuts. The
leads should face the front of the chassis.
3
I (V[ Connect the red-black transformer lead to
the lower (+) lug of the selenium rectifier
(S) .
2 ( '1 Twist the pair of white leads and dress
them from the power transformer to socket
VI. Connect one lead to pin #2 of VI (S).
Connect the other white lead to pin #8 of VI.
3('-) Twist the red pair of leads and dress them
to socket VI. Connect one red lead to pin
#4 of VI (S). Connect the other red lead to
pin #6 of VI (S).
4
(?1 Twist the pair of green leads together and
dress to socket V2. Connect one green
lead to pin 1/2 of V2. Connect the other
green lead to pin #7 of V2.
5 ('/1' Twist the brown pair and dress them to
socket V7. Connect one brown lead to pin
#2 of V7. Connect the other brown lead to
pin #7 of V7.
6 (
'1' Dress the brown -yellow and green -yellow
leads a I' 0 un d to the s even lug terminal
strip. Connect the brown -yellow to lug #7
and the green-yellow to lug #5.
7
(1.-1 Connect the red -yellow lead to the solder
lug near the filter capacitor.
8 (-1 Feed the red lead from the left 0u t put
transformer through both cable clamps and
the red lead from the right output trans-
former through the right clamp. Connect
both red leads to filter capacitor lug #1.
(The lead from the right output transformer
can be trimmed to the required length).
9 ('/) Feed the two choke leads through the right
cable clamp, con n e c t one lead to filter
capacitor lug #2 and the other lead to lug
4{ 1. (These leads can be trimmed as re-
qUired). Tighten the two nuts holding the
cable clamps.
10 (v') Dress the power transformer black leads
around the end bell and connect one lead to
lug Aof the fuse post (S). Connect other
black lead to lug #l of on -off switch (S).
11
('1 Connect the short black lead from the right
output transformer to lug #4 of the 4 screw
terminal strip. Connect the brown lead to
lug #3 (S). Connect the orange lead to lug
#2 (S). Connect the yellow lead to lug # 1.
Mount the quadruple section filter capacitor
in the special cutout. Fasten by twisting
each mounting tab one -quarter turn. Note
that the four connecting lugs are identified
by markings at the base of the lugs. Be
sure to orient the capacitor properly, with
the lugs positioned as in the pictorial.
Mount two solder lugs with a #4 screw and
nut next to the quad filter capacitor. This
is the main grounding point of the entire
amplifier and should be tightened securely
with the two lugs pointing as shown in the
pictorial.
10 (...y-Mount the power transformer, PA-060, in
the large center cutout. The wires should
face the front of the chassis. Fasten the
two mounting screws at the rear with #8
lockwashers and nuts. Place a cable clamp
over each of the two front mounting screws
and fasten loosely with 118 lockwashers and
nuts. The green, red, and white pairs of
wires should be threaded through the left
cable cI amp as should the green -yellow
and brown-yellow ones. Pass the brown
pair through the right clamp.
14 U)
MOST TRANSFORMER LEADS ARE PRE-CUT
TO THE PROPER LENGT HS AND DO NOT
REQUIRE CUTTING. HOWEVER, THEY CAN BE
SHORTENED WHERE DESIRED. IT IS ESSEN-
TIAL THAT THEY NOT BE CUT TOO SHORT
FOR CONNECTIONS WHEN THE LEADS ARE
POSITIONED
IN A C COR DAN C E WITH THE
PICTORIAL DIAGRAM. IN THE EVENT THAT
THE TRANSFORMERS ARE RETURNED TO THE
FACTORY FOR REPLACEMENT OR INSPEC-
TION, THE LE ADS ,MUST BE OF U SAB LE
LENGT HOR THE WARRANTY WILL BE
VOIDED.

12 ('1 Repeat step 11 for the left output trans-
former and the left screw terminal strip.
23 (v{ Connect the negative end of the other 50
MFD capacitor to lug #3 of the 7 lug strip
and the positive end to lug #1.
4
18 (v1 Repeat step 16 for connection of V2 and V3.
19 (VJ Repeat step 17 for connection of V3 to left
power takeoff socket.
14 (v) Repeat step 13 for right output transformer.
The blue lead is twisted with the green and
goes to pin #3 of V6 (8), green to pin #4,
while the blue-white and green-white, after
twisting together, are connected to pins #3
(8) and #4 (8) of V7.
32 ("'1 T rim the leads of a 6800 ohm (blue -gray-
red) resistor to 1". Connect one lead to
lug #1of the filter capacitor (8). Connect
the othe l' end to lug #4 of the filter capac itor.
30 ("1 Connect one end of a 3" wire to lug It 1of
the right s ide bias potentiometer (8). Con-
nect the other end to lug #1of the left side
potentiometer (8).
31 (t1" Connect one end of a 5-1/4" wire to lug #8
of VI (8). Connect the othe r end to lug #2
of the quad filter capacitor (8).
24 (0' Cut both leads of another 10,000 ohm (brown-
black-orange) resistor to 1". Connect one
end to lug #2 of the seven lug strip. Connect
the other end to lug It 1of the strip (8).
25 0' Connect one end of a 6" wire to lug #6 of
the 7 lug strip (8). Connect the other end
to the ground lug near the filter capacitor.
See pictorial.
26 (t..r Connect one end of a 6" wire to lug -# 3of
the 7 lug strip~, (S). Connect the other end
to lug 11 1of the left bias potentiometer.
27 ("1 Connect one end of a 6" wire to lug #4 of
the 7 lug strip (8). Connect the other end
to the negative (top) lug of the selenium
rectifie l' (8).
29 (V'j Connect one end of a 3" wire to lug #3 of
the right side bias potentiometer (8). Con-
nect the other end to lug #3of the left side
bias potentiometer (8).
28 (0' Connect one end of an 8" wire to lug #2 of
the 7 lug strip (8). Connect the other end
to lug #3 of the left bias control.
33 (.-1 Connect one end of a 15.6 ohm res istor to
the ground lug on base of V2 socket (8).
Connect the other end to pin #8 of V2.
34 (VI Strip both ends of a 5" wire 1/2". Feed
one end through pin #1 of V2 (8) and connect
it to pin #·8 of V2 (8). Feed the other end
through pin H8 of V3 (8) and connect to pin
411 of V3.
35 (0 Connect one end of a 4 -1/2" wire to pin #1
of V3 (8). Connect the othe l' end to pin #8
of the left power takeoff socket (8).
36 M Connect one end of the othe l' 15.6 ohm
resistor to the ground lug at the base of
socket V7 (8). Connect the other end to
pin #1 of V7.
Twist together a pair of 6" wires except
for 1-1/2" at each end. Connect one end of
one wire to pin #2 of V7 (8). Connect the
other wire to pin #7 of V7 (8). Connect one
of the other ends to pin #2 of V6. Connect
the remaining end to pin #7 of V6.
Twist together a pair of 7" wires except for
1-1/2" at each end. Connect one end of one
wire to pin #2 of V6 (8). Connect the other
wire to pin #7of V6 (8). Dres s the pair to
the front panel of the chassis and over tothe
right power takeoff socket. Connect one end
of the pair to pin #1 of the takeoff socket.
Connect the other of the twisted pair to pin
#2 of the takeoff socket.
20 (.q' Connect one end of a5" wire to lug #1of
the 7 lug strip. Connect the other end to
lug #6.
21 (0 Connect the negative end (-) of a50 MFD
capacitor to lug #4 of the seven lug strip.
Connect the positive (+) capacitor lead to
lug #1.
22 (t:1" Cut both leads of a 10,000 ohm (brown-black-
orange) res istor to 1". Connect one end of
the resistor to lug #4 of the 7 lug strip and
the other end to lug #3.
13 (-7 Twist the blue and green leads from the left
output transformer together and connect the
green lead to pin #4 of V3. Connect the
blue lead to pin #3 of V3 (8). Twist blue-
white and green-white together and connect
the blue-white lead to pin #3 of V2 (8).
Connect the green-white lead to pin #4 of
V2 (8).
17 (p1f
16 (0
15 (ur Connect the center (common) lead of the
double (2 x.02) disc capacitor to lug #6 of
the 7 lug terminal strip. Connect one of
the outside wires to lug #5 of the strip (8)
and the other outside wire to lug #7 of the
strip (8).

37 (-1 Strip both ends of a 5" wire 1/2". Feed
one end through pin #8 (8) and connect it to
pin #1 of V7 (8). Feed the other end
through pin #1 (8) of V6 and connect to pin
#8 of V6.
38 (v) Connect one end of a 4-1/2" wire to pin #8
of V6 (8). Connect the other end to pin #8
of the right power takeoff socket (8).
39 (I/j Connect one end of a 1000 ohm (brown-
black-red) resistor to pin #5 of V2 (8).
Connect the other end to pin #6. Repeat for
V3, V6 and V7. Keep the resistor pigtails
short (about 1/2") for all four of these
resistors.
40 (0{ Mount the printed circuit board PC -3 from
the bottom of the chassis. Note the num-
bers of the eyelets are upright when look-
ing from the rear of the chassis. Use a
4/40 screw, lockwasher and nut at each
mounting hole. The two wires from the
board s h a u Id be straightened carefully.
These are used at a later step.
In making solder connections to the printed
circuit board, all connections are made to
the numbered eyelets in the board. In this
way, there is no danger of damaging the
printed wiring or the components which are
part of the board as sembly. These eyelets
already have solder in them and it is very
easy to make sol de r connections to the
board. The lead wires should have their
ends stripped back about 1/4", and these
stripped ends should be tinned by heating
with a soldering iron and touching against
the solder. When the wire is to be soldered
to the eyelet on the board, the eyelet is
heated until the solder flows; and then the
wire end is pushed into the eyelet and held
in place until the solder sets. This type of
soldering can be done with a very small
iron, and it is preferable not to use any
more heat on the eyelet on the board than
is required to get the solder to flow.
41 (~Connect a 2-3/4" wire from eyelet #23 (8)
of the printed circuit board to pin #6 of V6
(8).
42 ('-1 Connect a 3" wire from eyelet U22 (8) to
pin tl6 of V7 (8).
43 (0 Connect a 3" wire from eyelet #19 (8) to
filter capacitor lug #3.
44 (tI) Cut the leads of a 22,000 ohm (red-red-
orange) res isto!' to 1". Connect one end of
the resistor to capacitor lug' #3 (8). Con-
nect the other end to capacitor lug 114.
45 (0 Connect a 3-1/2" wire from eyelet #20 (8)
to capacitor lug #4 (8).
46 ("1 Observe two wires extending from the
printed circuit board just under the input
socket. Connect the extended wire on the
right to the ground (short) lug of the right
input socket. Con n e c t the left extended
wire to the ground (short) lug of the left
input socket.
47 (V) Connect a 1-1/2" wire from eyelet #18 (8)
to lug #5 of the right power takeoff socket
(8).
48 (0 Twist together a pair of 3-1/4" wires.
Connect one pair of ends to eyelets # 15 (8)
and #16 (8). Connect the other ends to pins
#1 (8) and #2 (8) of the right power takeoff
socket.
49 (v') Connect one end of a 10 ohm (brown-black-
black) resistor from eyelet #10 (8) to pin
#3 of the right power takeoff socket (8).
50 ("1 Connect one end of a 2-1/2" wire to eyelet
# 21 (8). Connect the other end to lug #2of
the right potentiometer (8).
51 ('"1 Connect one end of a 5-1/2" wire to eyelet
#14 (8), and connect the other end to pin #4
of V6 (8).
52 (0 Connect a 2" wire from lug #3 of the input
switch (8) to the long lug of the right input
socket.
53 ({/) Connect one end of a 470,000 ohm (yellow-
violet-yellow) resistor to long lug of right
input socket. Connect the other end to the
ground (short) lug of the right input socket
(8).
54 (£11 Connect one end of a 470,000 ohm (yellow-
violet-yellow) resistor to lug #1of the input
switch (8). Connect the other end to the
ground short lug of the left input socket (8).
55 (0 Connect one end of a 1-3/4" wire to eyelet
#17 (8). Connect the other end to the long
lug of the right input socket (8).
56 (/.-1 Connect one end of a 3-1/2" wire to eyelet
#7 (8). Connect the other end to the long
lug of the left input socket.
57 (0 Connect a short link of wire from the left
input socket long lug (8) to lug 4i 2of the
input switch (8).
58 (0 Connect a 1-1/4" wire from eye let #3(8) to
pin 115 of the left takeoff socket (8).
5

59 (t/f" Con n e c t one end of a10 ohm, (brown-
black-black), I' e sis tor to eyelet #8 (8).
Connect the other end to pin #3 of the left
power takeoff socket (8).
60 (,;/) Twist a pair of 3-1/2" wires together and
connect one pair of ends to eyelets #4 (8)
and #5(8). Connect the other pair of ends
to pins #1 (8) and #2 (8) of the left power
takeoff socket.
61 (vj Connect one end of a 2-1/2" wire to eyelet
#2 (8), Connect the other end to pin #6 of
V3 (S).
62 (0 Connect one end of a 3-1/2" wire from
eyelet #1 (S). Connect the other end to pin
#6 of V2 (8).
63 (I/) Connect one end of a 2-1/2" wire to eyelet
#6(S). Connect the othe I' end to lug #2of
the left potentiometer (S).
64 (V) Connect one end of an 8" wire to pin #4 of
V3 (8). Connect the other end to eyelet
#11 (8). It is important to keep this wire
close to the chassis and carried around the
printed cir cui t board, as shown in the
pictorial.
65 (0 Connect one end of a 5" wire to eyelet #9
(8). Connect the other end to solder lug
near filter capacitor.
66 (r/) Connect one end of a 12" wire to lug #1of
the left screw terminal strip (S). Connect
the other end to eyelet #12 (S). See
pictorial.
67 ("1 Connect one end of a 10-1/2" wire to lug
#4 (S) of the- teft screw terminal strip.
Connect the""'other end to the solder lug
near filter capacitor.
68 «(.)) Connect one end of a 9 -1/2" wire to lug #1
of the right screw term ina 1 strip (S).
Connect the other end to eyelet # 13 (8). See
pictorial.
69 (e-j Connect one end of a 9" wire to lug #4 (8)
of the right screw terminal strip. Connect
the other end to solder lug near capacitor.
70 (v) Connect short link of wire from capacitor
ground lug (8) to solder lug near capacitor.
Solder all six wires which go to the pair of
solder lugs.
71 ( ) Insert the line cord through the grommet in
the rear of the chassis. Pull through about
five inches, tie a knot and then pull from
the outside till the knot is a g a ins t the
grommet. Separate the two conductors of
6
the line cord to the knot then strip about
1/2" of insulation from each end. Connect
one end to lug Bof the fuse post (S). Con-
neet the othe I' end to lug #2 of the on -off
switch (S). This completes the wiring of
your amplifier.
It is wise to go back and check all connec-
tions for correctness and for good solder-
ing. All hardware should also be checked
for tightness. The fuse can now be in-
stalled in the fuse post on the rear of the
chassis. The four rubber feet should then
be pushed into the four holes in the bottom
plate - from outside tow a I' d inside and
seated with a twisting motion.
INITIAL ADJUSTMENT
Plug in the EL-34 tubes V2, V3, V6 and V7.
Also plug the 7199 tubes into pI' in ted circuit
sockets. Do not plug in GZ-34 rectifier tube. If
an 0h m met e I' is available, measure resistance
from capacitor lug #2 to ground. This should be
in excess of one hundred thousand ohms. Inspect
wiring to make sure that all joints are soldered
and that no parts are shorting together. Plug line
cord into 117 volt ac line and turn on switch.
While tubes are warming up, set the bias adjusting
potentiometers to the c en tel' of their rotation.
This is approximately the correct setting and can
serve as an emergency operating adjustment if no
test instruments a I' e available. (H 0 WE V E R,
OPERATION WITHOUT CORRECT BIAS ADJUST-
MENT 18 NOT RECOMMENDED A8 IT RE8ULT8
IN POOR PERFORMANCE AND PROBABLE
DAMAGE TO COMPONENTS.)
Your D y n a kit includes Dyna Biaset (patent
pending) which greatly simplifies setting of the
bias voltage. This can now be done with the most
simple and inexpensive types of dc meters as long
as they have a rating of 1000 ohms per volt or
higher. The correct setting of the bias provides a
total cathode current for each pair of EL-34 tubes
of 100 mao This current through the precision
15.6 ohm resistors produces a voltage drop of
exactly 1. 56 volts dc, and this v0 It age can be
checked at pin #8 of each preamplifier power take-
off socket. 1. 56 volts is also the voltage which is
furnished by a "0" type flashlight dry cell .. Thus
any fresh cell of this type can be used for an
accurate reference standard for bias setting.
The procedure for setting the bias is to meas-
ure the voltage output of a "D" type dry cell and
note the meter reading. Then insert the positive
meter probe in the pin #8 hole of the left pream-
plifier power socket (note that outside the chassis
the pin n u m bel's are counted counterclockwise
from the keyway while inside the chassis they are
counted clockwise). The negative met e r probe

should touch the c has sis. P lug in the GZ -34
rectifier tube, and in about 10 seconds there will
be a current flow which will cause a meter deflec-
tion. As the rectifier warms up, the reading will
increase. The left bias potentiometer should be
adjusted until the meter reading at pin #8 is the
same as across the dry cen (this reading will be
1.56 volts if the meter is of sufficient accuracy).
This adjustment should then be made using the
right bias potentiometer and measuring the voltage
at pin 118 of the right power takeoff socket. Then
repeat the setting for the left control and left set
of tubes. There may be Some drifting of the read-
ing as the tubes heat, but this will stabilize within
15 minutes after which no further adjustment is
required. Small variations will occur with line
voltage changes. These will have no effect on
performance. A It h au gh the setting is a semi-
permanent one, at times of tube replacement or
similar repair or maintenance work, resetti.ng of
the bias will preserve peak performance and keep
distortion at an absolute minimum.
If in the course of bias setting it is found that
the control range of the potentiometer is insuffi-
cient to obtain the correct setting, do not operate
the amplifier until the cause of the difficulty has
been established. Operation with incorrect bias
can lead to damage to the output tubes and/or other
components.
Note that the use of pin #8 as directed in the
wiring instructions means that this pin cannot be
used as a connection point for preamplifiers if the
preamplifiers take power from the power takeoff
sockets of the front panel. Most preamplifiers do
not require the use of this pin. However, for those
which do, some other pin must be used as a bias
check point. If no other pin is available, the
connection from pins 1/8 of V3 and V6 to the pre-
amplifier power sockets must be omitted; and bias
measurements should be based on voltages read
directly at pin #8 of V2 or V3 for the left channel
or pin 1i8 of V6 or V7 for the right channel.
PREAMPLIFIERS
The Dynakit Stereo 70 can be used with any
conventional stereo or monophonic preamplifier,
or pair of monophonic preamplifiers. Preamp-
lifiers which con t a i n their own built-in power
supply can be used by connecting their audio cables
to the input socket. Those units which require
power from the amplifier can be readily used with
the Dynakit provided that the power sockets on the
front panel of the Dynakit are properly wired. The
preceding instructions include the proper wiring
for both Dynakit and Heathkit WA-P2 preamplifiers
so that these can be inserted without modification.
Should others requiring different socket connec-
lions be used, the socket wiring can be changed to
suit their requirements.
PROTECTIVE COVER
The protective cover which is supplied with the
Stereo 70 has been designed to be both functional
and good looking. It should be used on the amplifier
if the amplifier is located where it can be inadver-
tently to u c h e d by anybody. There is voltage
appearing above chassis on the printed circuit
board which is not lethal, but which can give an
uncomfortable shock. In addition, the tubes get
hot in normal operation, and touching them can
result in a minor burn. Therefore, the protective
cover should generally be used.
The amplifier should be located where there is
adequate ventilation - at least one foot of space
above it and afew inches all around. The amplifier
can be located away from other elements of the
high fidelity system so there should be no need to
put it in too confined a space. NEVER put anything
on top of the cover which can obstruct air flow.
Always use the amplifier with the tubes in vertical
position.
The cover and bottom plate arc affixed at the
same time. The amplifier chassis should be set
over the bottom plate, the cover lowered over the
chassis, and then the three pieces are fastened
together with the six sheet metal sc rews through
the chassis sides.
USING THE STEREO 70
The Dynakit Stereo 70 is designed to be used in
any of three different modes of operation: stereo-
phonic use in which separate stereo channels are
carried through the two sides of the amplifier;
high-low frequency amplification where one chan-
nel carries the low frequencies and the other the
high frequencies with a frequency dividing network
ahead of the amplifier; and monophonic use with
the two channels paralleled so that 70 watts of
power are available.
In stereo use, the stereo 70 provides 35 watts
per channel. A stereo preamplifier's two output
cables, or other left and right signals, are con-
nected to the input jacks of the ste reo 70. The
input switch is set to "stereo", and remains in that
pos ition whenever two input cables are connected,
allowing the preamplifier to do all the switching.
The right loudspeaker is connected to the "right"
screw terminal strip between the "c" terminal and
the terminal corresponding to the speaker's im-
pedance. The left loudspeaker is similarly con-
nected to the "left" terminal strip.
If there are two monophonic preamplifiers
which require power from the amplifier, each is
connected to the respective preamplifier power
takeoff socket. As provided, these will accom-
7

modate Dynakit monophonic preamplifiers without
modif
ication.
The stereo 70 can be turned on and off from
the back panel switch, or this switch can be left in
"on"
position, and the amplifier switched from one
of the switched ac outlets on the associated pre-
amplifier.
High-Low frequency amplification
For this type of operation the input switch on
the Stereo 70 should be put to "stereo" position.
The low frequency output of the dividing or cross-
over network should be fed to the left input, and
the "left" loudspeaker output should be connected
to the bass speaker. The high frequency output of
the diViding or cross -over network should be fed
through the right channel, and the tweeter con-
nected to the "right" loudspeaker terminal strip.
Monophonic 70 watt amplification
For monophonic operation, the two channels of
the Stereo 70 may be paralleled. For this, only
one input
cable is connected to either the left or the
right input (but not both), the input switch is set to
"mono", and the outputs are connected together.
An insulated wire jumper should be connected from
"c" to "c" on the screw terminal strips. Another
insulated wire jumper should be connected from
"8" to "8" if a 4 ohm loudspeaker is used, or from
"16" to" 16" is an 8ohm or 16 ohm loudspeaker is
used. When using the 16 ohm loudspeaker in this
fashion, the amplifier's maximum power output is
not as great because of the impedance. mismatch,
but there is no loss of power when using a 4 ohm
or 8ohm loudspeaker as specified above. The
maximum power available intoa16 ohm loudspeaker
is still 55 watts, however, and there is a compen-
sating factor. The distortion, as levels below max-
imum, will be reduced by this type of connection.
What happens
is that the operating conditions are
shifted from maximum power output to minimum
distortion. This same operation can also be
achieved, of course, by connecting an 8ohm loud-
speaker to paralleled 8ohm taps, or a 4 ohm
loudspeaker to paralleled 4ohm taps. Note that
whenever the two outputs are paralleled, only one
input
cable should be used, the other input socket
should not be used, and the switch is on "mono".
It is also practical to use the "mono" position
with a single input source with two separate loud-
speakers. In this case, each speaker is connected
to one of the screw output strips using the imped-
ance which pertains to the respective speaker. No
jumpers are required between the output strips.
Amonophonic preamplifier wh i c h requires
power from the amp 1 if ie r can be connected to
either of the two power takeoff sockets.
8
ENJOYING STEREOPHONIC SOUND
S tel' e0 ph 0n i c sound 0 if e r s an important
enhancement of enjoyment of your high fidelity
system. The proper setup and use of your stereo-
phonic system will bring considerable satisfaction.
However, stereophony introduces problems in high
fidelity reproduction which can dim in ish your
enjoyment of your hi fi system unless these prob-
lems are understood and corrected. These few
notes on the subject should assist materially in the
installation and use of a stereophonic system which
adds to your listening pleasure.
The pieces of equipment to be used should be
as similar as possible in each channel. This is
particularly true for the loudspeaker to be used.
Different types and brands of speakers have very
great differences in frequency response and other
important characteristics. If, for example, one
speaker has a peak in response at a certain fre-
quency where the other does not, the stereophonic
balance will be changed at that frequency. The
need for frequent rebalancing is due to this type
of dissimilarity.
There has been a relatively high proportion of
dissatisfaction with stereo which has arisen be-
cause of the attempt to attach an inferior second
channel to complete a system. If this channel
differs from the first channel it frequently destroys
any potential benefits of stereophonic sound.
The proper reproduction of monophonic discs
through the stereo system requires the cancella-
tion of identical signals (of opposite phase) so that
there is no unwanted vertical signal component in
the output. This requires either the parallelling
of the two sides of the cartridge or the parallelling
of the outputs of identical preamps. If the preamps
are slightly different, the vert i cal components
cannot be eliminated properly. In Dynakit pre-
amplifiers, the critical components which deter-
mine the response characteristics of the preamp-
lifier playback characteristics have a tolerance
of only 1% so that this pro b I e m cannot cause
difficulty.
Channel
phasing is a problem of stereo which
is readily solved, once understood. If, on a single
sound, one speaker cone moves inward while the
other moves out, the s y s t em is not properly
phased, and the sound area between the speakers
will lack homogeneity. All tapes and all discs are
now reproduced so that their phasing is consistent.
Therefore, once phasing of the playback equipment
is set it can be maintained for all tape and disc
sources without further change.
To check for proper phasing, playa monophonic
recording so that one signal comes through both
channels. Then move back and forth between the
speakers. If phasing is correct, there will be a

smooth transition of sound between the speakers.
If it is not correct, there will be an intermediate
area where the sound will shift -from one to the
other. If phasing is not correct, it can be rectified
by interchanging the two leads between one of the
amplifier c h ann e I s and its associated speaker.
There should be no need to change phasing once
the system is set up properly.
Proper phasing of the stereo pickup or tape
head is generally accomplished by the manufac-
turer of this item. However, this can be inverted in
installation if directions are not followed precisely.
If there is a drop in volume using amonophonic
tape or disc, this indicates probable incorrect
phasing. An interchange of ground and "hot" side
of one of the cartridge channels or of the two leads
to one channel of the tape head will remedy this
type of incorrect phasing.
Hum is another problem which the stereo disc
playback cartridge can introduce. In some cases
(particularly where independent preamps are used
for the two channels) the use of a common ground
lead on the two inputs will provoke a hum condi-
tion. For this reason, many stereo pickup manu-
facturers provide separate ground connections for
each channel by using four cartridge terminals.
The cable shields of the two channels should be
kept separated.
If a three terminal magnetic cartridge arrange-
ment is used, it is very possible that hum will be
encountered if the equipment from the two channels
has any additional interchannel connection (beside
the common shield from the pickup). Connection
of
the Stereo 70 should not give this trouble. How-
ever, dissimilar units in each channel can be a
source of hum when three terminal cartridges are
used. Crystal and ceramic cartridges which go
into high
level inputs should not normally introduce
this type of hum problem.
Positioning of loudspeakers will af fee t the
quality of stereophonic reproduction. Generally,
moderate distances of six to ten feet along the
same wall pro vi d e the best effect. If greater
spacing is required, the use of a blend control can
help to provide "fill" in the middle. However, if
extreme distance is required, a "phantom" middle
channel is useful. It has generally been established
that an L+R combination of the two channels pro-
vides the best center fill. Information on the proper
method for obtaining this signal, using either the
two regular stereo amplifiers, or a third ampli-
fieI', may be obtained on request from Dynaco,
Inc.
This arrangement will also provide a com-
bined signal for a remote monophonic extension
speaker.
In most rooms, the proper balance of the
stereo system will be different for different listen-
ing positions. If the listening positions are rela-
tively far from the s pea k e I' s, this problem is
diminished, and' optimum results are obtainable
for several listening positions simultaneously.
The most basic consideration of the installation
and use of a stereophonic system is that stereo
alone does not create realism and high quality
sound. Two low
grade stereo channels will not
give
the qua 1 it Yof one high grade monophonic
channel. There is no substitute for high quality
components, carefully installed.
IN CASE OF TROUBLE
Your Dynakit Stereo 70 has been designed to be
as free from trouble as possible. However, a
mistake in assembly or a defective component can
affect its performance or m a k e it inoperative.
Some trouble-shooting procedures are suggested
in case difficulty is encountered. Naturally the
wiring should be checked very carefully to make
sure that all con nee t ion s have been made in
accordance with instructions.
The tubes should light after afew seconds of
warmup. If they do not, it is probable that there
is no ac voltage getting into the amplifier, which
indicates a possible blown fuse.
Fuse failure
If fuses blow frequently without apparent cause,
this may sometimes be rectified by using aslow
blow type of
fuse. However, do not exceed the 3
ampere fuse rating when replacing fuses.
If fuses blow within 30 seconds of turning the
amplifier on, remove the GZ -34 rectifier tube and
see if this cures the problem. If it does, the
rectifier may be bad and another should be tried.
A5U4GB type of rectifier can be substituted for
trial purposes, although using this tube type will
cut down the maximum power rating of the ampli-
fieI'. If the GZ -34 is not at fault, the quadruple
section filter capacitor may be snorted. Generally,
shorts in this section of the amplifier will show up
in a
measurement of resistance (with the amplifier
unplugged from the 117 volt line) from capacitor
to ground. This resistance should exceed 100,000
ohms.
Fuses blowing with all tubes removed indicate
either m i s wi l' in g or a defective PA-060 power
transformer.
Tubes glowing
If one (or a pair) of the EL-34's glows a bright
red color after slight warmup, it is possible that
the tube is bad, or there may be afault in the bias
supply which supplies neg at i v e voltage to the
EL-34' s, measurable (with ahigh impedance meter
such as aVTVM) at pin #5 of each EL-34. The
9

actual value of negative voltage will depend on the
setting of the respective bias potentiometer. With
the Biaset con n e c t ion reading the proper 1.56
volts, the negative voltage at the EL-34 tubes
should be within 20% of minus 32 volts. If the two
tubes in a pair have different negative voltages
at pin #5, as measured by aVTVM, this is a clue
to a defective component or wiring. (V2 and V3
make one pair; V6 and V7 make the other pair).
A small difference in voltage indicates either a
runaway tube (which can be checked by borrowing
the pair from the other channel) or a leaking .1
mfd capacitor on the PC-3 board. If one tube has
no negative voltage, it indicates that there is an
open connection from the bias supply to this tube.
If no meter is available, it is possible to pin
down the fault with a glowing tube by switching the
two tubes of the pair. In the same socket exhibits
the glow, the fault is in the amplifier bias supply
or components. If the same tube glows in trans-
posed position, it is most like~a defective tube.
The tubes sup P lie d with the Stereo 70 are
matched and should be completely interchangeable.
When making replacements of tubes, they should
preferably (although not absolutely essential) be
replaced in pairs which are matched. There is
no need to maintain matching of all four EL-34
tubes.
In emergencies, substitution of the tubes can
be made with at her tube types. The 5881 and
KT -66 can be used in place of the EL-34's provided
the bias is readjusted to give 1.56 at the Biaset
check point. The 5U4G or 5U4GB can be used in
place of the GZ -34. There is no substitute for the
7199 tube.
No signal
If there is no signal coming through the ampli-
fier, each side should be checked separately to
see whether one channel may be working. If one
works, and the other does not, the working channel
can be used for test purposes. For example, the
tubes can be interchanged to determine whether
they will work in eithe r channel. In this way, a
defective tube can be singled out.
It is advisable to remove the input cable and
see whether insertion of the plug makes a "thump"
through the loudspeaker. Sometimes, a defective
cable or pre amp prevents signal from coming
through while the amplifier itself is operative. If
there is no signal from the preamplifier, but a
"thump" can be induced by unplugging the shielded
cable from the preamplifier or by inserting the tip
of a small screwdriver into the input socket, then
the fault is not in the amplifier but in the associated
equipment.
If a meter is available, voltages should be
checked in comparison with the voltage table in-
10
'\.~-----------
eluded in these instructions. Departures of more
than 10% from the values shown indicate possible
malfunctioning of some of the circuit components.
Hum and noise
If excessive hum or noise appear, it is neces-
sary to determine whether they occur within the
amplifier. Sometimes noise in the preamplifier is
blamed on the amplifier. The simple test is to
remOve the cables from the input socket and see
whether the same noise is present. If the noise is
removed when the cable is unplugged, it is in the
preceding equipment which should then be checked.
If not, it is probably in the amplifier.
Compare the noise in the two channels. If
both are the same, it is not likely to be tubes like
the 7199 or EL-34 which affect only the channel in
which they operate, but it could be the GZ-34 or
the quad capacitor or bias capacitors which are
common to both sides of the circuit.
Sizzling sounds coming through the loudspeaker
may come from poor can t act s between circuit
elements and chassis. Make sure that ground
connections are tight.
In some rare cases, loud pops may be heard
through the loudspeakers. These can come from
poor conditions inside the pins of the EL-34 tubes.
Touching a hot soldering iron to these pins will
rectify this. Make sure that solder is not deposited
on the pin or the tube may not fit the socket.
In the event that trouble shooting will not cor-
rect the problem, factory consultation is available
without charge, and factory service at moderate
charge.
FACTORY SERVICE AND GUARANTEE
The Dynakit Stereo 70 is designed to provide
good service over a long period of time. It is
intended to be used at the conventional 117 volt
line input found in most homes. Operation up to
125 volts will not cause any problem. Above that
voltage, it is suggested that a voltage regulating or
adjusting device be used in order to protect the
components in your amplifier. The normal guar-
antee on the equipment is not applicable if it is
used above the 125 volt rating.
All parts in the Stereo 70 are guaranteed for a
period of one year from purchase except tubes
which carry the standard EIA guarantee of 90 days.
Parts which are defective will be replaced at no
charge if they are returned prepaid to the factory
either directly or via the dealer from whom the kit
is purchased. Many Dynaco dealers carry spare
parts in stock to facilitate replacements. After
the guarantee period is past, Dynaco will supply
any non-standard parts used at net prices. Parts

which are standard dealer items can be purchased
from most electronic supply stores.
If transformers are returned for factory repair
or exchange, they should be removed from the
equipment without cutting the leads short. If leads
have been cut rather than unsoldered, so that they
are no longer usable, the guarantee on the trans-
former is voided.
In the event that the assembled kit does not
function properly or breaks down after some use,
Dyna Company will service the kit for a service
fee of $7.50 plus the cost of parts which have been
damaged by the user or are past the guarantee
period. This service facility is not available for
kits which are incompletely wired, or have been
wired with other than rosin core solder, or in
which
changes or modifications have been made
without fa c tor y authorization. In addition, NO
PARTS WILL BE REPLACED NOR WILL ANY
SERVICE
BE AVAILABLE FOR KITS WHERE
THE GUARANTEE POST CARD HAS NOT BEEN
RETURNED. THE SERIAL NUMBER ON THIS
INSTRUCTION BOOK MUST
BE MENTIONED IN
CORRESPONDENCE, PARTS RETURN, OR KITS
RETURNED
FOR FACTORY SERVICE. It is the
factory prerogative to limit the service facility to
one year from date of purchase.
When shipping the amplifier for service, a note
must be attached specifying the symptoms, the
name and address of the sender, and the serial
number of the unit. The kit should be securely
packed with stuffing inside the cover to prevent the
tubes from falling out of the sockets. It should be
placed in a rugged carton surrounded by several
inches of shredded paper or other soft packing
material. The original carton is not suitable for
shipp ing a wired amplifier.
Shipment should be made by prepaid Railway
Express, where possible; and repaired kits will be
returned by Railway Express COD for freight and
service charges unless these charges have been
prepaid. Parcel post is not a safe method for
shipment of completed kits and should not be used.
Dyna Company assumes no responsibility or
liability for dam age s or injuries sustained in
assembly or operation of the Dynakit.
STEREO 70 PARTS LIST
(Parts of similar type which do not change performance may sometimes be included as a matter of expediency).
1 - Chassis set (including cover and bottom plate)
1 - Power Transformer - PA-060
2 - Output Transformers - A-470
1 - Choke - C-354
4 - Output Tubes - EL-34
1 - Rectifier Tube -GZ -34
2 - Driver Tubes -7199
7 -
Octal sockets
1 - Printed Circuit Assembly - PC-3
1 - Filter Capacitor -Quad @525V
2 -
Capacitors -50 MFD
1 - Dual Ceramic Capacitor - 2 x .02 MFD
1 - Selenium Rectifier
2 - Four Screw Terminal Strips
1 - Fuse Post plus rubber washer and mounting nut
1 - Fuse -3A Sio-Blo
1 - Line Cord
1 - On-Off Switch (SPST)
1 -
Input Switch (SPDT)
1 -
Dual Input Socket
1 - Input Socket Insulator
2 - Potentiometers 10,000 ohm
1 - Seven Lug Terminal Strip ~
1 - Hank Wire
RESISTORS
2 -
15.6 ohms
4 - 1000 ohms (brown-black-red)
2 - 10,000 ohms (brown-black-orange)
2 - 470,000 ohms (yellow-violet-yellow)
2 - 10 ohms (brown-black-black)
1 - 6800 ohms (blue-grey-red)
1 - 22,000 ohms (red-red-orange)
4 - Rubber Feet
33 - 4/40 x 1/4" Screws
31 - 4/40 Nuts
30 -#4 Lockwashers
1 - 4/40 x 3/4" Screw
4 - #6 Sheet Metal Screws
10 - 8/32 Screws
14 - 8/32 Nuts
14 -#8 Lockwashers
1 - Rubber Grommet
2 - Solder Lugs
2 - 3/8 Lockwashers
2 - 3/8 Nuts
2 - Cable Clamps
1 - Set Instructions & Pictorials
11

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*MATCHED 1%
oPREAMP POWER TAKEOFF POINTS

*Measurements at these points vary from tube to tube and do
not indicate wbether performance is normal.
HMeasurements at these points can only be made with avacuum
tube voltmeter. The two tubes in a pair should have identical
readings.
2ol10·yolt
120·..,olt
1
-<
VIOLET ~
II WHITE
BLACK
II WHITE
VIOLET ~
SPECIAL INSTRUCTIONS FOR OPTIONAL
120.240 VOLT POWER TRANSFORMERS
BLACK
Stereo 70s supplied with power transformer PA-521 may be connec-
ted for either 120 volt
or 240 volt AC operation as follows:
For 120 Volt Operation
1 ( )
Twist together the black and black-white leads, and
connect both to lug Aof
the fuse post (5).
2Twist together the violet and violet-white leads, and
connect both to lug #1 of the on-off switch (5).
For 240 Volt Operation
1 ( ) Connect the black lead to lug Aof the fuse
post (S).
2 ( ) Connect the violet lead to lug #1 of the on-ofT switch (5).
3 ( ) Twist together the violet-white and the black-white leads,
and solder them together. Insulate this connection with
electrical tape.
When connected for 240 volt operation, a 1~ampere slow blow fuse
should be used.
Printed circuit
Eyelets
#3 and #18
370 volts dc
Selenium rectifier
Bottom (+) lug 50 ac
Top (-) lug -65 dc
VOLTAGE
TEST POINTS
Pin #Any EL-34 GZ-34
Either 7199
11.56 *
2
->
435 *
3410 *
u360 ac u
4
I'<l
415
oj 1->
5
'<!'
-32** ~->
<.0
<D
6
-32**
360 ac 1.0
7
->
0
81.56 435 *
9*
Capacitor lug
A • 305
B
'" 375
C415
D
... 435
117 V AC
PA-060
BL
+
20
10K-
+.50+.50
B~i C
-.;,
22 K6.8 K
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