Dynaco FMA 2 Service Manual

Page 1

SERIAL NUMBER

This number must be men-

F MA_2 I NS E RT iioned in all tommunica-
tions concerning Dynakii.
AM PLI FIE R

ASSEMBLY INSTRUCTIONS

Price 50¢

DYNA COMPANY EJJWJAMJ :2::A::"::.1°1f:::

Page 2

FHA-2 INSERT AMPLIFIER

DESCRIP'IION

The Dynakit FMA-2 is a semi-selfpowered 10 watt
amplifier designed to fit inside the FM-l Dynatuner. It
occupies the chassis cutout presently provided for the
Dynaeo multiplex adapter. This amplifier provides full
high fidelity performance within its power rating. convert-
ing the Dynatuner into a complete FM radio (less loud-
speaker). At the same time. the tuner can still function
independently as an ultra sensitive, low distortion, wide
band tuner.

The performance of the FMA 2 is on a quality level not
normally found in amplifiers of low power rating. lt pro-
vides 10 watts at less than 1% distortion within 1 db from
30 cycles to 15,000 cycles. Its frequency response is 1
db from 12 cycles to 35.000 cycles. Transient response is
excellent, permitting clean transfer of 10.000 cycle square
waves and critically damped low frequencies.

A unique power supply configuration borrows power
from the present Dynntnner power supply. Using additional
silicon diodes to obtain a negative voltage. Operating volt-
ages in the Dynatimcr are unaffected by operation of the
FMA 2 because the power supply of the FM-l tuner was
designed with extra load capacity. The GBQ5/El.84 output
tubes operate with the inverted power supply. A .l2AX7
voltage amplifier and phase inverter stage, uses the FM-I
power supply, an arrangement which completely eliminairst
undesired coupling betwem low and high level amplifier
stages. :he use of a miniaturized high quality output trans-
former ot' patented Uynaeo design permits a high feedback
factor and low distortion over a wide band.

The FMA-Z can be used with its own loudspeaker while
audio signals may be taken from the A output socket to
feed an amplifier I'with or without preamplifier) and
another loudspeaker. It is also practical to use the Wynn-
tuner to furnish signal to an external multiplex adaptor
(see the Appendix of the FM-l instruction manual) inde-
pendently of the use of the FMAQ. There is no harm in
removing the loudspeaker connected to the FMA»2 and
using the Dynatuner in normal fashion. The amplifier is
designed so that it can operate without a speaker
connected.

ASSEMBLY

You will first assemble the etched circuit board, and
then mount it and the other components on the chassis of
your Dynatuner and complete the wiring. Note that the
top of the etched circuit board diagrams the position of
each component The identification symbol for each part is
marked between the holes into which its leads will be
inserted. Resistors may be identified by comparing them
with the color code provided on the parts list. The first
color is nearest the end of the resistor, and any fourth color
band should be ignored. Capacitors will be individually
identified. Other special components will be identified as
they are called for in the assembly process.

It is important that all components be mounted close to
the board. Refer to the FM 1 instruction manual for
detailed instmctions on proper wiring and soldering tech-
niques. A GOOD SOLDERING eOB IS ESSENTIAL
TO THE PROPER PERFORMANCE OF YOUR RE-
CEIVER. ALL SOLDERENG MUST BF. DONE WIT}:
ROSIN CORE SOLDER. Whenever soldering is required,
the instructions indicate it by "(S l If this symbol is not
shown after a connection is specified, it indicates that
further connections will be made at that point before
soldering.

When soldering a part to the etched circuit board. (low
the solder from the lead onto the board so that no ball of
solder is evident, but rather a smooth transition from sol
der to component lead. and to the board. The solder must
completely surround the component lead. Do not apply
excessive solder. but do not hesitate to apply sufficient.
heat to assure a smooth flow of solder all around the lead
and onto the board. Be sure that all terminals are soldered
to the copper on the board, as well as to the lead. Cut ofi
all leads as close to the bottom of the board as pomihle,
alter soldering. This is essential. since the clear continua cf
the tuner allow only 1/," clearance from the board to the
EMA-2 chassis.

PC-9 Etched Circuit Board Assembly

U. ) Mount all of the one-hall wutt resistors. RF? through
R62. onto the board. Keep them flush against the
board. Solder all leads and cut off the excess close
to the board.

21' 1 Mount the one-watt resistor R63 and the threwwutt
resistor R64. Solder each lead and cut ofi the excess
close to the board.

3. 5 Mount the small capacitors CSl. C56 and C57. Keep
them right against the board. Solder each lead and
cut off the excess.

44 l Mount the rectangular capacitors C52. C53, CS4.
055 and (158. Solder each lead and cut off the
excess. The direction in which these capacitors face
is not important.

5( l Mount the connecting terminals #51 through #64.
When the small end is inserted in the hole, they
snap lightly into place. Solder each, and cut the
excess ed on the bottom (copper side) of the board.

6( ) Mount the three 9 pin sockets on top of the board.
Note the orientation of the flat side of each socket.
Make sure each lab penetrates the board, and bend
the tips over for a secure mechanical connection.
Solder each pin carefully. Note that in use, the
tubes will plug into the bottom of the sockets, on the
side of the board opposite to that on which other
components are mounted.

Page 5

PARTS LIST

Parts of similar type which do not change performance
may sometimes be included as a matter of expediency. This
will account for slight variations in value and appearance.

V, wan refiners

R 51 27 .000 ohms
R 52 1 50,000 ohms
R 53 220.000 ohms
R 54 1,500 ohms brown-green-red

R 55 470.000 ohms yellow-violct-yellow
R 56 470.000 ohms yellow-violetvyellow
R 57 47.000 ohms yellow-violct-orange
R 58 47,000 ohms yellow-violet-orange
R 59 470.000 ohms yellow-violet-yellow
R 60 470,000 ohms yellow-violet-yellow
R 61 470,000 ohms yellow-violet-yellow
R 62 10.000 ohms brown-blackorange

red-violet-orange
brown-green-yel low
red-red-yellow

1 wall resistor

R 63 33 ohms orangeorange-black

3 we" rod-tor

R64 1800hms

Capacitors

C 51 10 mmfd disc
C 52 .0068 mid

C 53 .02 mfd

C 54 .02 mid

C 55 .1 mid

C 56 10 mmld disc

C 57 220 mmfd

C 58 .068 mid

C 59 40/40 mfd @ 350 volts electrolytic

l2AX7/ECC83 - V5]
63Q5/EL84 - V52 and V53
PC-9 etched circuit board

9 pin socket for etched circuit board
silicon diode- D51 and D52
chassis plate

F-561 filament translormer
2-499 output transformer

3 screw terminal strip

Fuse, 2 amp

piece hookup wire
Instruction Manual
Warranty Card

HO-I-ll-HHPFNWHMH

Hardware

6 #6/32 x V, machine screws
14 #6 lockwashers
18 (6/32 nuts

2 l sleeves for 86 screw

2 l6/32 x 2%" machine screws

VOLTAGE CHECK POINTS

All voltages are measured between the point indicated and the chassis. using a vacuum tube voltmeter. All voltages are
measured with the volume control at minimum. Voltages indicated by (it) must be measured only between the points indi-

cated, as these points are -300 volts.

PIN!
TUBE 1 2 3 5 6 7 8 9
V 51 12AX7/ECO33 180 48 49 6.3 AC 6.3 AC 90 0 7 0
V 52 63Q5/EL84 ~305 -305 -295 3.3 M? -2 -5.5 0 0
V 53 68Q5/EL84 -305 -305 -295 6350* -2 -5.5 0 0
Terminal #52 6.3 AC Terminal #58 Terminal #61 -5.5
Terminal #55 -5.5 to 6.3 Acl' Terminal #62 245 AC
Terminal 459 -300 Terminal #59 Terminal #63 245
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