Dynaco ST 35 Service Manual

Page 1

SERIAL NUMBER

14635013

This number must be men-
tioned in all communica-
tions concerning Dynakit.

INSTRUCTIONS FOR THE ASSEMBLY AND USE OF
DYNAKIT STEREO 35 POWER AMPLIFIER

Price $1.00

04641 4

DYNA COMPANY mama 2:1:A1°;:::*.:":::

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Description

General Wiring Practice
Mechanical Assembly
Wiring instructions

240-Volt Transformers

Installation

In Case of Trouble 1

Part List

Schematic Diagram

CONTENTS

°°OOUI#W

11

Back Cover

SPECIFICATIONS

Power Output:

Frequency Response:

Power Response:

lntermodulation Distortion:

Hum and Noise:

Sensitivity:

Input Impedance:

Output Impedance:

Damping Factor:

Minimum Channel Separation:
Power Consumption:

Tube Complements:

Size:

Shipping Weight:

35 watts continuous, 45 watts
IHFM Music Power (both channels)

ildb from 10 cps to 40,000 cps.

20 cps to 20,000 cps without
exceeding 1% distortion within
1 db of 17,5 watts each channel.

Less than 1% at 17,5 watts each
channel. Less than 0.1% at
average listening levels.

Inaudible; more than 80 db below
rated output.

1 volt input for 17.5 watts out-
put (each channel).

500,000 ohms.

8 and 16 ohms.

10 from 20 cps to 20,000 cps.
80 db.

100 watts, 50/60 cycle a.c.

7247 (2), GBQSIEL84/7l89 (4),
silicon diodes (2).

4" high, 13" wide, 5/z" deep.
16 lbs.

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If hum and noise are present to any unusual degree, first
remove the inputs plugs from the Stereo 35, and replace
them with short-circuited input plugs (or temporarily con-
nect a jumper between eyelets l and 2 on each circuit
board). If the hum and noise become virtually inaudible,
the amplifier is probably working properly, and the cause
should be sought elsewhere in the system. If plainly audible
hum or noise persist, there may be an error or defective
component in the power supply, or an open ground con-
nection. If the hum is in one channel of the amplifier only,
check to see that eyelet #2 of its circuit board is soldered
to the input ground lug. Occasionally, a bad tube will cause
this condition, which is easily determined by switching
tubes until the hum appears in opposite channel. Hum
on both channels is probably due to a power supply defect,
a bad capacitor section or defective diode.

Intermittent hum, noise or silence are usually the result
of a poor solder connection. If the trouble occurs in both
channels, check the power supply first; if in one channel
alone, examine the solder connections on that side.

Filament glow is normal, but if the plate (the large
metal area) of a tube tends to glow red, either the tube or
its associated circuitry is faulty, It all four of the output
tubes glow in this manner, there is a short circuit in either
the cathode (pin #3 of any 6BQ5) or filament (pin #4
and #5), or at lug '#4 of the filter capacitor.

The voltage chart printed alongside the schematic dia-
gram may be helpful in trouble-shooting. lf readings made
at any of the points indicated differ from those listed by
more than 10%, it is likely that a wiring error or defective
component is nearby in the circuit.

The Stereo 35 should never be operated with any of its
tubes removed from their sockets.

FACTORY SERVICE AND WARRANTY

The Stereo 35 is designed to provide reliable, trouble-
free performance for a long period of time. when properly
assembled and installed. It is intended for use with the
lZO-volt ac power supplied to most homes. Although varia-
tions of several volts above or below this figure will have no
pronounced effect upon performance or component life, the
normal guarantee on the equipment is not applicable if it
is operated with ac. inputs greater than 130 volts. If your
local power is this high or higher in voltage, it is suggested
that a voltage regulating or adjusting device be installed
to protect the amplifier.

All parts used in the Stereo 35 are guaranteed for a
period of one year from the date of purchase except tubes,
which carry the standard electronic industry (EIA) 90-day
warranty. Defective parts will be replaced at no charge if
they are returned prepaid to the factory either directly or
via the dealer from whom the kit was purchased. Many
Dynakit dealers carry parts in stock which may be used
for replacements. After the guarantee period has passed,
Dynaco, Inc. will supply any non-standard parts used at
net prices. Parts which are standard (resistors, capacitors,
tubes) can generally be purchased from a local electronics
supply store.

If it is believed that a transformer is defective, it should
be disconnected by unsoldering, never by cutting its leads
so short that it cannot be re-used.

If the kit has been completely assembled, yet cannot be
made to function properly, or if difficulty is apparent after
a short period of use, we will service the kit for a fixed
charge of $6.00, plus the cost of the parts which are outside
the warranty or have been damaged by the user.

Factory assembled amplifier include a one-year war-
ranty on labour as well as parts.

IMPORTANT: FIXED-CHARGE SERVICE AND
MAINTENANCE ARE NOT AVAILABLE FOR
KITS WHICH ARE INCOMPLETELY WIRED,
OR KITS WIRED WITH SOLDER OTHER THAN
ROSIN CORE TYPE, OR KITS PHYSICALLY
OR ELETTRICALLY MODIFIED WITHOUT
PRIOR FACTORY AUTHORIZATION. ADDI-
TIONALLY, NO PARTS WILL BE REPLACED
AND NO SERVICE MADE AVAILABLE FOR
KITS FOR WHICH THE WARRANTY POST
CARD HAS NOT BEEN RETURNED. THE
SERIAL NUMBER ON THE FRONT COVER OF
THIS INSTRUCTIONS BOOK MUST BE MEN-
TIONED IN ALL CORRESPONDENCE AND IN
ANY CASE WHERE PARTS ARE RETURNED,
OR KITS SENT OR BROUGHT TO THE FAC-
TORY FOR SERVICE.

It is the factory prerogative to limit the service facility
to one year from the date of purchase.

When shipping the amplifier to Dynaco, Inc., for service,
attach a note specifying the symptoms, the name and
address of the sender, and the serial number of the kits.
The kit should be securely packed to withstand the abuses
of handling in transit. It should be placed in a rugged car-
ton surrounded by several inches of shredded paper or
other soft packing material. The original kit carton is not
suitablefbr shipment Ufa wired amp/i ier.

Shipment should be made by prepaid EXPRESS, where
possible, repaired kits will then be returned EXPRESS
C:O:D: for freight and service charges (unless these charges
have been prepaid). Parcel post is not a safe method for
the shipment of assembled kits, and should not be used
for this purpose.

The Dyna Company assumes no liability or responsibility
for damages or injuries sustained in assembly or operation
of this Dynakit.

STEREO 35 PART LIST

_.

Chassis set
(chassis, cover and bottom plate)

1
1

1 Power Transformer PA-774 1 Line Cord with Plug

2 Output Transformers Z-565 2 Input Sockets

4 Output Tubes 6B05/EL84/7189 1 Roll Hookup Wire

2 Driver Tubes 7247 2

2 Rectifier Diodes 500 ma 1000 PIV (Silicon)

1 Quadruple Section Filter Capacitor

60/40/20 @450 v.; 100 @ 25V. RESISTORS

2 3-Screw Terminal Strips 1 50 ohms, 5 watts

1 Fuse Holder with Rubber Washer and 1 95 ohms, 5 watts

1 Circular Nut 1

5-Lug Terminal Strip
Fuse 2-Ampere SIo-Blo

PC-13 Circuit Board Assemblies 12

6,800 ohms (blue-gray-red), 1 watt 1

HARDWARE

4 Rubber Feet

1 1A" Grommet
12 8/32 x /4" Machines Screws
12 8/ 32 Nuts
#B Lockwashers

25 4/40 x /A" Machine Screws
25 4/40 Nuts

25 #4 Lockwashers

4 #6 Sheet Metal Screws

1 Instruction Manual with Pictorial Diagrams
Warranty Card

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