Techron 7550 User manual

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E ®
7550
POWER
SUPPLY
AMPLIFIER
Techron
Division
of
Crown
International,
Inc.,
1718
W.
Mishawaka
Road,
Elkhart,
IN
46517-4095
© 1992 Crown Intemational, inc
K80507-5

TECHRON
LIMITED ONE-YEAR WARRANTY
SUMMARY OF WARRANTY
CROWN INTERNATIONAL, INC., 1718 W. Mishawaka Road, Elkhart, Indiana 46517 (Warrantor) warrants to the ORIGINAL
COMMERCIAL PURCHASER ONLY of each NEW TECHRON product, for a period of one (1) year from the date of purchase by
the original purchaser (warranty period) that the product is free of defects in materials or workmanship and will meet or exceed all
advertised specifications for such a product. This warranty does not extend to any subsequent purchaser or user, and automatically
terminates upon your sale or other disposition of our product.
ITEMS EXCLUDED FROM WARRANTY
We are not responsible for product failure caused by misuse, accident or neglect. This warranty does not extend to any product on
which the serial number has been defaced, altered or removed. It does not cover damage to loads or any other products or accessories
resulting from Techron product failure. It does not cover defects or damage caused by your use of unauthorized modifications,
accessories, parts, or service.
WHAT WE WILL DO
We
will
remedy
any defect
in
materials
or
workmanship
by
repair,
replacement,
or
refunds.
If
a
refund
is
elected,
then
you
must
make
the
defective
or
malfunctioning
component
available
to
us
free
and
clear
of
all
liens
or
other
encumbrances.
The
refund
will
be
equal
to
the
actual
purchase
price,
not
including
interest,
insurance,
closing
costs,
and
other
finance
charges
less
a
reasonable
depreciation
on
the
product
from
the
date
of
original
purchase.
Warranty
work
can
only
be
performed
at
our
authorized
service
centers
or
at
our
factory.
Expenses
in
remedying
the
defect
will
be
borne
by
Crown,
including
one
way
surface
freight
shipping
costs
within
the
United
States.
(Purchaser
must
bear
the
expense
of
shipping
the
product
between
any
foreign
country
and
the
port
of
entry
in
the
United
States
and all taxes, duties, and other custom’s fee for such foreign shipments.)
HOW TO OBTAIN WARRANTY SERVICE
-~
You
must
notify
us
of
your
need
for
warranty
service
not
later
than
ninety
(90)
days
after
expiration
of
the
warranty
period.
We
will
give
you
an
authorization
to
retum
itto us
for
service.
All
components
must
be
shipped
in
a
factory
pack
or
equivalent
which,
ifneeded,
may
be
obtained
from
us
for
a
nominal
charge.
Corrective
actions
will
be
taken
within
a
reasonable
time
of
the
date
of
receipt
of
the
defective
product
by
us.
If
the
repairs
made
by
us
are
not
satisfactory,
notify
us
immediately.
DISCLAIMER OF CONSEQUENTIAL AND INCIDENTAL DAMAGES
YOU
ARE
NOT
ENTITLED
TO
RECOVER
FROM
US
ANY
CONSEQUENTIAL
OR
INCIDENTAL
DAMAGES
RESULTING
FROM
ANY
DEFECT
IN
OUR
PRODUCT.
THIS
INCLUDES
ANY
DAMAGE
TO
ANOTHER
PRODUCT
OR
PRODUCTS
RESULTING FROM SUCH A DEFECT.
WARRANTY ALTERATIONS
NO
PERSON
HAS
THE
AUTHORITY
TO
ENLARGE,
AMEND,
OR
MODIFY
THIS
WARRANTY.
THE
WARRANTY
IS
NOT
EXTENDED
BY
THE
LENGTH
OF
TIME
WHICH
YOU
ARE
DEPRIVED
OF
THE
USE
OF
THE
PRODUCT.
REPAIRS
AND
REPLACEMENT
PARTS
PROVIDED
UNDER
THE
TERMS
OF
THIS
WARRANTY
SHALL
CARRY
ONLY
THE
UNEX-
PIRED PORTION OF THIS WARRANTY.
DESIGN CHANGES
We
reserve
theright
to
change
the
design
of
any
product
from
time
to
time
withoutnotice
and
withno
obligation
to
make
corresponding
changes in products previously manufactured.
LEGAL REMEDIES OF PURCHASER
There
is
no
warranty
which
extends
beyond
the
terms
hereof.
This
written
warranty
is
given
in
lieu
of
any
oral
or
implied
warranties
notcontained
herein.
WE
DISCLAIM
ALL
IMPLIED
WARRANTIES,
INCLUDING
WITHOUT
LIMITATION
ANY
WARRAN-
TIES
OF
MERCHANTABILITY
OR
FITNESS
FOR
A
PARTICULAR
PURPOSE.
No
action
to
enforce
this
Warranty
shall
be
commenced
later
than
ninety
(90)
days
after
expiration
of
the
warranty
period.
TECHRON division of Crown International, Inc.
_
1718
W.
Mishawaka
Road,
Elkhart,
IN
46517-4095
Downloaded from www.Manualslib.com manuals search engine

TECHRON. 7550 Power Supply Amplifier Rev. 0
aon
List of Effected Pages
Revision 0 November, 1992
Page Revision Page Revision
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Warranty
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TECHRONs 7550 Power Supply Amplifier Rev. 0
-
Table
of
Contents
Section
1.
Introduction
.........
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1-1
1.1.
General
Description
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1-1
1.2.
Mechanlcs
........
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1-1
1.3.
Citcultry
2.0...
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1-2
1.4.
Service
Policies
.......6
2...
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1-2
1.5.
About
this
Manual...
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ences
1-2
Section
2.
Installation...
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2-1
2.1.
Unpacking
......
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2-1
2.2.
Mounting
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2-1
2.3.
HOOKUP
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2-3
2.3.1.
Dual
Channel
Hookup
«2...
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2-3
2.3.2.
Mono
Hookup
..............
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25
2.3.3.
INPUTS
2.
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2-5
2.3.4.
Outputs
................00.
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2.3.4.1.
Load
Wires
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2-7
2.3.4.2.
Load
Protection
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2-7
2.3.5.
AC
Power.
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2-8
Section
3.
Operation...
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2...
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3-1
3.1.
Operating
Precautions
.........
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3.2.
FUNCHONS
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Protection
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3.4.
Fuse
Replacement
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3-5
Section
4.
Specifications
and
Performance
..................ecc0
4-1
4.1.
General
Specifications
..........
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4-1
4.2.
Dual
Channel
Specifications
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4-2
4.3.
Mono
Specifications
....
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42
4.4,
Performance
2...
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43
Section
5.
Theory
of
Operation
............
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5-1
5.1.
General
Concepts
...........
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Circuit
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5-1
Section
6.
Applications.............
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6-1
6.1.
Introduction
to
the
Applications
Section
...........2..-cccceuuaace
6-1
6.2.
Special
Operation
Modes
for
Increased
Output
..............0.00005
6-1
6.2.1.
Push-Pull
Operation
for
Increased
Voltage
....................000006,
6-1
6.2.2.
Paralleling
Channels
for
Increased
Current
.....
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6.3.
Input
Modifications
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6-2
6.3.1.
Low
Frequency
Interrupt
..............
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6-2
6.3.2.
Balanced
Active
Input
(Module
75A06)......................0.
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6-2
6.3.3.
Balanced
Transformer
Input
(75A07)
..
0.000.000
00
cece
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6-2
6.4.
Constant
Current
Operation
for
Special
Needs
(75A08)
...............
6-2
6.5.
AC
Power
Conversion
.......
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6-3
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TECHRONs
7550
Power
Supply
Amplifier
Rev.
0
Illustrations
INustration
1-1
Model
7550
2.0...
cece
cee
tee
re
eee
e
een
tneenene
1-1
Illustration
2-1
Mounting
Demensions
....
0.2.2.0...
0.
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ete
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etter
ees
2-1
Illustration
2-2
Dual
Channel
Hookup
.........
20.
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cree
nee
e
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eaten
2-2
illustration
2-3
Mono
Hookup
.........-
cc
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reece
nee
eet
eee
ee
enees
2-4
Wustration
2-4
Input
Capacitor
Chart
..
0.2.00...
cece
cee
teen
etree
ene
neens
2-5
Iustration
2-5
RF
input
Filters...
2.0...
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teaes
2-6
Illustration
2~6
Wire
SlzeNomograph
...........---
Lec
ceeceecceneevnsvaueeeees
2-7
Iilustration
2-7
Inductive
Load
Protectlon
...
2.2.0.2...
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27
lilustration
2~8
Fuse
Selector
Nomograph
.........-
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2-8
Ilustration
3-1
Front
Panel
Functions
............05002-e
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3-2
Hlustration
3-2
Back
Panel
Functlons
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3-3
Illustration
3-3
Fuse
Selectlon
Table
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35
Illustration
41
Power
Matrix
.......
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4-3
Itustration
4-2.
Nominal
Frequency
Response
..........0.
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44
Iustration
4-3.
Nominal
Phase
Response
.......
0.2.
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illustration
4-4
Power
Output
Response
............0esseees
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45
Illustration
4-5
Nominal
Crosstalk
2.0.0...
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4-5
Illustration
4-6
Low
Frequency
Interrupt
Actlon
........
06.
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46
illustration
4-7
Nomimal
Output
Impedance
........
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illustration
4-8
Nomimal
Nolse
Spectrum
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INustration9-9
Typical
IM
Distortion
.........
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48
Iustration
5-1
Circuit
Block
Diagram
2.0...
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5-3
Illustration
6-1
Internal
AC
Connections
......
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6-3
Illustration
6-2
Schematic
JO004—2
Power
Supply
.......0..
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64
Illustration
6-3
Schematic
JOOOSAS
Display
Module
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6-5
Illustration
64
Schematic
JOOO3A2
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TECHRON, 7550 Power Supply Ampilfier
Rev. 0
Illustration 1-1 Model 7550
Section 1. Introduction
1.1. General Description
The TECHRONs* 7550 (shown above) is a high-
powered, industrial power supply amplifier,
single or dual channel. Read this manual com-
pletely to familiarize yourself with the details
of this amplifier.
Model 7550 provides precision amplification of
electrical signals with frequencies from zero
(de) to 20 kHz. It accomplishes this with ex-
tremely low harmonic and intermodulation dis-
tortion and low noise.
The continuous average power output is 90
watts minimum per channel into an 8 ohm
load. Bridge the amplifier and operate it as a
mono unit with 180 watts minimum power out-
put into a 16 chm load.
The rugged aluminum chassis measures five
and a quarter inches high, nineteen inches
wide, and almost twelve inches deep.
1.2. Mechanics
. On the front panel, the push button power
switch activates an amber ON indicator. Green
SIGNAL PRESENCE indicators confirm signal
path
from
input
to
output.
Directly
above
these
are red JOC® indicators which indicate clipping
and STANDBY conditions.
Use the front panel output monitor jack with a
high
impedance
load
to
monitor
the
output.
Ad-
just the output level with the two controls on
the front panel.
On the back panel are alternate means of input
and
output
connection.
Connect
an
unbalanced
input to either BNC jacks or barrier strip
screws,
and
a
balanced
input
to
an
optional
in-
put
module.
Connect
output
to
banana
jack
binding posts or barrier strip screws.
Other
features
on
the
back
panel
include
a
mono/dual
switch,
a
grounding
barrier
strip,
and
a
three-wire
AC
line
cord
with
fuse.
*
TECHRONe
is
a
division
of
Crown
International,
Inc.
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—_
Introduction

TECHRONs 7550 Power Supply Amplifier
Rev. 0
1.3. Circuitry
The output transistors operate in the Techron-
designed Multi-Mode® AB + B configuration in
which
quiescent
current
is
carried
by
the
driver
stages
until
the
output
transistors
are
sum-
moned by a large current demand.
Techron
tests
each
of
the
16
rugged
150
watt
output
transistors
to
verify
the
safe
operating
area
of
each
device
which
enhances
the
amplifi-
er’s
overall
reliability.
Massive
black-anodized
heat
sinks
thermally
joined
with
the
chassis
enable
the
entire
ampli-
fier
to
function
as
a
heat
sink.
In
the
event
of
overheating,
the
thermal
sensing
circuit
will
place
the
amplifier
in
the
STANDBY
mode.
After
cooling,
the
unit
will
return
to
normal
operation.
Frequent
overheating
may
indicate
the
need
for
the
optional
forced
air
cooling
sys-
tem.
See
Section
NO
TAG
V-I
current
limiting
provides
protection
against
damage
from
shorted
and
low
impedance
loads,
overloaded
power
supplies,
input
overload,
and
high
frequency
overloads.
A
four-second
turn-
on
delay
provides
initial
load
protection.
1.4. Service Policies
Due
to
the
sophisticated
circuitry
of
Model
7550,
have
only
qualified
and
fully
trained
technicians
perform
service
work.
Return
to
the
factory
in
original
packing
for
service.
Re-
placement
packing
is
available
from
Techron.
When
returning
Model
7550,
enclose
a
brief
letter
explaining
as
completely
as
possible
all
problems.
Include
your
address
and
telephone
number.
Ship
“UPS™
ground”
to:
TECHRON
Customer
Service
Department
57620 C.R. 105
Elkhart, Indiana 46517
Phone: [phone]
FAX: [phone]
1.5. About this Manual
Special instructions (Danger, Warning, Cau-
tion,
and
Note)
appear
throughout
this
manual.
Examples of each follow:
A
ve
Danger
is
used
before
instructions
that
|
expose
the
reader
to
a
hazard
that
will
|
cause
Injury
or
death.
The
hazard
will
be
explained
and
Instructions
to
avoid
the
hazard
will
be
Included
In
the
warning.
|
A Warning is used before Instructions
|
that
expose
the
reader
to
a
hazard
that
may cause Injury or death. The hazard
will be explalned and instructions to
avold
the
hazard
will
be
Included
In
the
warning.
ae
en
ZN CAUTION
A
Caution
is
used
before
Instructions
that
if
not
performed
properly,
could
cause
equipment
damage.
The
condition
will
be
explained
and
instructions
to
avold
the
conditlon
will
be
Included
In
|
the
warning.
Note:
A
note
is
used
when
information
needs
special
emphasis
that
does
not
call
attention
to
a
hazard.
The
rest
of
this
manual
contains
complete
in-
formation
on
installation,
operation,
specifica-
tions,
performance,
theory,
and
applications.
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1-2
Introduction

TECHRON,» 7550 Power Supply Amplifier Rev. 0
Section 2. Installation
sme qe —
To
reduce
the
risk
of
ELECTRIC
SHOCK
Do
not
Install
Model
7550
Into
a
smail
or
FIRE
HAZARD,
do
NOT
expose
Model
sealed
chamber
of
any
kind.
Improper
7550
to
rain
or
molsture.
operation
and
overheating
will
result.
2.1. Unpacking Provide a source of cooling air for the fan in-
take. A vent tube to the outside of the rack may
be necessary if the rack ventilation is poor and/
or the amplifier heat output is high. NEVER
Every Techron Model 7550 is thoroughly in-
spected and tested prior to leaving the factory.
Carefully
unpack
and
inspect
the
unit
for
dam-
block
the
air
vents
in
the
sides,
front,
and
back
of
the
amplifier.
Allow
a
clearance
of
1.75
inches
(4.5
cm)
above
the
unit
for
hot
air
dis-
charge,
if
at
all
possible.
age in shipment. If damage is found, notify the
transportation company immediately. Save the
shipping carton and packing materials as evi-
ae dence of damage for the shipper’s inspection.
Techron will cooperate fully in the case of any
shipping damage investigation. In any event,
save the packing materials for later use in
transporting or shipping the unit. Replacement
packing materials are available from Techron.
Always ship this amplifier in proper and appro-
priate packing material.
2.2. Mounting
The PSA-2X amplifier is designed for standard
19-inch (48.3 em) rack mounting as well as
stack mounting without a cabinet. When rack
mounting, take care to support the heavy am-
plifier from behind. Use end supporting angles
joined to the sides of the rack to support the
amplifier from beneath.
If chassis slides are used, care should be taken
to avoid toppling the rack when the slides are
extended. The center of gravity of the amplifier
is approximately 5.4 inches (13.7 em) behind
the front panel.
k
14.75in
2.125 In-~|
5S
Sacm
If
a
number
of
units
are
being
racked
on
electri-
cally
common
rails,
remove
the
strap
from
the
~
rear-panel
ground-terminal
strip
to
maintain
a
very
high
signal/noise
ratio.
This
will
reduce
the
possibility
of
ground
loop
hum.
Illustration
2-1
Mounting
Dimensions
2-1
installation
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TECHRONe 7550 Power Supply Amplifier
Rev. 0
CHANGE THE DUAL-MONO SWITCH
ONLY WITH THE AMP TURNED OFF
INPUT
SOURCES
«
CHANNEL 2
IN
CHANNEL 1
IN
ovaL—! L_e mono
Model 7550
CHANNEL 1 |
OUT +
DUAL
MODE
LOADS
CHANNEL 2
OUT -
Illustration
2-2
Dual
Channel
Hookup
2-2
Installation
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TECHRONe 7550 Power Supply Amplifier
Rev. 0
2.3. Hookup
Before beginning the installation of your ampli-
fier, please note the following:
e Remove all power from the unit. Do not
have the AC cord plugged in.
© Turn input level controls down (fully
counter clockwise).
The input and output jacks are located on the
rear panel. Use care in making connections,
selecting signal sources, and matching loads.
During hookup take the following precautions:
1. Use only shielded cable on inputs. The
higher the density of the shield (the
outer conductor), the better the cable.
Spiral wrapped shield is not recom-
mended.
2. The output wire and connectors should
be heavy enough to carry the intended
current to the load.
3. Use good quality connectors with proper
strain relief.
* Do not use connectors that have any
tendency to short circuit.
¢ Do not use connectors that can be
plugged into AC power receptacles,
¢ Do not use 1/4-inch phone plugs that
short the high level outputs.
4. Keep unbalanced input cables as short
as possible—avoid lengths greater than
10 feet.
5.
Do
not
run
signal
(input)
cables
together
with high
level
wiring
such
as
load
(out-
put)
wires
or
AC
cords
(this
helps avoid
most
hum
and
noise).
6.
Do
not
short
the
ground
lead
of
an
out-
put
cable
to
the
input
signal
ground.
Oscillations
may
result.
For important considerations about hooking up
Inputs, Outputs, and AC power, see sections
2.3.3., 2.3.4., and 2.3.5.
The Model 7550 may be operated in either
DUAL
(two-channel)
or
MONO
(single-channel)
mode.
Your
hookup
will
depend
on
which
mode
you decide to use. There are very important
wiring differences between these two modes.
2.3.1. Dual Channel Hookup
To
put
the
amplifier
in
Dual
mode,
slide
the
Dual-Mono
switch
at
the
back
of
the
amplifier
(See
Illustration
2-2)
to
the
DUAL
position.
Be
very
careful
not
to
short
the
two
outputs
to-
gether
while
in
Dual
mode
and
observe
correct
polarity.
The
installation
is
very
intuitive
in
DUAL
mode.
The
input
of
Channel
1
feeds
the
output
of
the
same
channel
as
does
the
input
of
Chan-
nel
2.
LN CAUTION
Never
parallel
the
two
outputs
to-
gether
or
parallel
them
with
the
out-
put
of
any
other
amplifier
without
Techron
approved
modifications.
See
|
Section
6.2.2,
ae
Paralleling
the
outputs
does
not
safely
increase
power
output
and
can
cause
the
unit
to
prema-
turely
go
into
Standby
mode
to
prevent
over-
heating.
Note:
The
two
channels
of
Model
7550
may
be
operated
in
parallel
under
certain
specific
conditions.
See
Section
6.2.2.
“Par-
alleling
Channels
for
Increased
Current”.
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2-3
installation

TECHRONs
7550
Power
Supply
Amplifier
Rev.
0
CHANGE
THE
DUAL-MONO
SWITCH
ONLY
WITH
THE
AMP
TURNED
OFF
DO NOT
Modal 7550
rrtleae
"KO C
DO NOT USE BLACK
BANANA JACKS
pe
MONO
MODE
+
LOAD
Illustration
2-3
Mono
Hookup
2-4
installation
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TECHRONs 7550 Power Supply Amplifier
Rev. 0
2.3.2. Mono Hookup
To
put
the
amplifier
in
Mono
mode,
slide
the
Dual-Mono
switch
at
the
back
of
the
amplifier
(see
Ilustration
2-3)
to
the
MONO
position.
Mono mode is quite different from Dual mode.
Switching
to
the
Mono
position
alters
input
cir-
cuitry of Model 7550 so that the two internal
amplifiers
work
as
a
push-pull
team
for
single
channel output.
In this mode use only the Channel 1 input. DO
NOT
USE
THE
CHANNEL
2
INPUT.
Signal
level and quality may be greatly degraded.
Keep
the
level
control
of
Channel
2
turned
com-
pletely down (counter clockwise).
Note:
The
input
jack
and
level
control
of
Channel
2
are
not
defeated
in
MONO
mode.
Any
signal
fed
into
Channel
2
will
combine
with
the
signal
in
Channel
1
and
result
in
distortion.
Channel
2
input
alone
will
result
in
low
power
output.
The
output
wiring
is
very
different
too.
The
polarity
of
the
output
of
Channel
2
is
inverted
so
it
can
be
bridged
with
the
output
of
Channel
1.
The
outputs
of
both
channels
receive
the
same
signal
from
the
input
of
Channel
1.
The
most
common
hookup
(see
Illustration
2~3)
connects
the
positive
lead
from
the
load
to
the
red
post
or
positive
terminal
of
Channel
1
and
the
negative
lead
to
the
red
post
or
positive
ter-
minal
of
Channel
2.
The
inner
black
posts
are
not
used.
Note:
Mono
output
is
balanced
and
is
iso-
lated
from
the
chassis
and
from
the
input
grounds.
Thus,
both
output
leads
are
con-
nected
to
the
red
or
“hot”
connectors
only.
A\ CAUTION
Be
certain
that
all
equipment
(meters,
switches,
etc.)
connected
to
the
MONO
OUTPUT
LINES
Is
not
grounded.
Both
sides
of
the
line
must
be
totally
isolated
from
the
Input
grounds
to
Model
7550.
Failure
to
observe
this
precaution
will
result
in
severe
oscillation.
Note: Use of ungrounded test equipment
may violate local codes.
2.3.3. Inputs
The
inputs
are
unbalanced,
have
a
nominal
im-
pedance
of
25
k
ohms
and
will
accept
most
line-
level
outputs.
There
are
three
precautions
to
take
when
connecting
to
the
inputs:
1)
Keep
undesirable
signals
off
the
inputs;
2)
Avoid
ground
loops,
and;
3)
Avoid
feedback
between
an
output
and
an
input.
Low
frequencies
are
sometimes
present
in
the
input
signal
and
can
overload,
overheat
or
oth-
erwise
damage
loads.
To
remove
such
frequen-
cies
as
well
as
any
DC
that
may
also
be
present,
place
a
capacitor
in
series
with
the
in-
put
signal
line.
The
graph
in
Illustration
2—4
shows
how
the
value
of
the
capacitor
affects
the
frequency
response.
Use
only
a
low-leakage
paper,
mylar
or
tantalum
capacitor.
Illustration
2-4
Input
Capacitor
Chart
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2-5
Installation

TECHRON,
7550
Power
Supply
Amplifier
Rev. 0
If
large
amounts
of
ultrasonic
or
RF
(radio
fre-
quency)
are
found
on
the
input,
place
a
low-
pass
filter
on
the
input.
While
high
RF
levels
may
not
damage
the
amplifier,
they
can
burn
out
sensitive
loads,
and
activate
the
amplifier’s
protection
system.
The
following
filters
are
rec-
ommended
for
such
situations:
bom
RO ml ire
— wl T wo
Wat: ALed Mg con be rarenead w
RO by an eppranate resiotet.
Illustration
2-5
RFI
Input
Filters
Improper
grounding
allows
feedback
oscillation
to
occur.
DO
NOT
CONNECT
INPUT
&
OUT-
PUT
GROUNDS
TOGETHER.
In
some
cases,
even
the
AC
power
line
may
provide
this
feed-
back
path.
Isolation
of
input
grounds
and
com-
mon
AC-line
devices
may
be
necessary.
2.3.4. Outputs
A
WARNING
ELECTRIC
SHOCK
HAZARD.
Output
potentials
can
be
lethal.
Make
con-
nections
only
with
AC
power
OFF
and
Input
signals
removed.
ns
When
connecting
outputs,
consider
the
follow-
ing
precautions:
—_
e¢
Use
quality
output
connectors.
If
banana
plugs
are
used,
be
sure
to
keep
connectors
snug
fitting.
Frequent
misuse
damages
and
loosens
these
connectors.
¢
Use
proper
output
wire
gauge
and
length.
See
nomograph,
Illustration
2-6
for
proper
wire
selection.
«
To
prevent
spurious
oscillations
and
un-
desired
feedback,
carefully
lace
output
cables
together.
Never
route
output
ca-
bles
with
input
cables.
*
Donot
join
amplifier
input
and
output
grounds
externally
to
the
unit.
¢
Never
connect
the
output
to
a
power
sup-
ply
output,
battery,
or
AC
power
main.
«
Consider
the
power
handling
capacity
of
your
load
before
connecting
it
to
the
am-
plifier.
Techron
is
not
liable
for
damage
to
any
Load
due
to
overpowering.
*
The
use
of
load
protection
fuses
is
highly
recommended
(see
section
2.3.4.2.).
Downloaded from www.Manualslib.com manuals search engine
2-6
installation

TECHRONs: 7550 Power Supply Amplifier
Rev. 0
2.3.4.1. Load Wires
Use cables of sufficient gauge (thickness) for
the length used. Otherwise, power is lost
through cable heating and resistance. Refer to
the nomograph (Illustration 2-6) below for rec-
ommended wire sizes.
Example Shown:
AL - Sota Ag - 0.16 obs,
Cable Length = 50%; anewer: #12 wire
Illustration 2-6 Wire Size Nomograph
Use the nomograph as follows:
1. Note the load resistance connected to
each channel of the amplifier. Mark this
value on the nomograph “Load Resis-
tance” line.
2. Note the “Reference Point” on the
nomograph.
3. Draw a pencil line through these two
points, intersecting the “Source Resis-
tance” line.
4. On the “2-Cond. Cable” line, mark the
length of cable run.
5. Draw a pencil line from the intersection
point on the “Source Resistance” line
through the mark on the “2-Cond. Ca-
ble” line.
6.
Where
the
pencil
line
intersects
the
“An-
nealed Copper Wire” line indicates the
wire gauge required.
2.3.4.2. Load Protection
Loads that are primarily inductive such as
transformers require special attention. To pre-
vent large low-frequency currents from damag-
ing the transformer (and prevent the Model
7550 from unnecessarily activating its protec-
tion system) it may be necessary to install a
capacitor in series with the load. If you are un-
sure whether this is necessary, measure the DC
resistance across the terminals of each load
with an ohmmeter. If the resistance you meas-
ure is less than 3 ohms either add the following
parts as shown in Illustration 2-7 or add an
appropriate high-pass filter or contact Techron
Engineering for further information.
Place an external non-polarized capacitor of
590
to
708
mfd
and
a
4
ohm
power
resistor
in
series
with
the
positive
(+)
lead
as
shown
be-
low:
dorm, 2W
FROM
AMP
INDUCTIVE
Load
OOOO GNO
Mlustration
2-7
Inductive
Load
Protection
We
recommend
that
you
protect
your
loads
from
damage
resulting
from
excessive
power.
A
common
way
to
do
this
is
to
put
a
fuse
in
se-
ries
with
the
load.
Fuses
help
prevent
damage
due
to
prolonged
overload,
but
provide
essentially
no
protection
against
damage
from
large
transients.
To
minimize
this
problem,
use
high-speed
instru-
ment
fuses
such
as
the
Littlefuse™
361000
series.
If,
on
the
other
hand,
the
load
is
only
suscepti-
ble
to
damage
caused
by
overheating,
use
a
fuse
or
circuit
breaker
having
the
same
slow
thermal
response
as
the
load
itself
such
as
a
slow-blow
fuse.
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Se ee
2-7
Installation

TECHRON, 7550 Power Supply Amplifier
Rev. 0
Illustration 2-8 is a nomograph showing what
size fuse to use according to the impedance and
peak power rating of the load.
«
{
rrr
ryy
t
! y
” 4
}
Mut
HHH
Liy
i
Example: Z = 3 ohms,
Peak Power = 750
|
Anwar. Fuse = 1.54 ’
{yt
v
1
1
TPT
]
rTrt
LOAD
IMPEDANCE
(Z)
in
ohms
|
T
| 1
FUSE
in
ampe
(A)
Voi
yg
®
|
|
T
r 1
J q
}
my
Illustration
2-8
Fuse
Selector
Nomograph
2.3.5. AC Power
Connect
Model
7550
to
proper
AC
current.
Supply
voltage
must
be
50
to
60Hz
and
no
more
than
10%
above
or
below
the
selected
line
volt-
age.
Failure
to
comply
with
these
frequency
limits
may
damage
the
unit
and
will
result
in
unreliable
operation.
Model
7550
may
be
operated
at
various
line
voltages.
The
serial
plate
indicates
factory
volt-
age
wiring.
The
tag
attached
to
the
line
cord
also
indicates
the
voltage
for
which
the
ampli-
fier
is
connected.
Five
standard
line-voltage
connections
are
of-
fered:
100,
120,
200,
220
and
240
VAC.
To
con-
vert
from
one
voltage
to
another,
see
Section
6.5.
Only
a
competent
technician
should
at-
tempt
to
convert
from
one
voltage
to
another.
Replace
the
FUSES
whenever
AC
voltage
con-
version
is
made
or
when
they
have
blown.
See
Section
3.4.
for
fuse
values
and
replacement
procedure.
The
amplifier
is
furnished
with
a
standard
three-wire
(grounded)
AC
plug.
Use
third
wire
ground
with
caution,
as
this
may
introduce
a
ground
loop
into
the
system.
If
a
ground
loop
is
present,
remove
ground
shorting
strap
on
the
back
panel.
See
[Illustration
3-2.
Three-to-two
wire
AC
plug
adapters
are
com-
mercially
available
for
adapting
to
a
two-wire
system
if
necessary.
Techron
assumes
no
Hlablility
whatsoever
for
ungrounded
operation
which
may
violate
UL
or
local
electrical
codes.
At
this
point,
installation
is
complete.
Read
the
next
section
to
familiarize
yourself
with
the
operation
and
functions
of
Model
7550.
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2-8
installation

TECHRONs, 7550 Power Supply Amplifier
Rev. 0
Section 3. Operation
A. WARNING
Never operate Model 7550 with
cover panels removed because
you could be ELECTROCUTED. |
Refer servicing to qualified
personnel.
3.1. Operating Precautions
Although your amplifier is well protected from
any external faults, we recommend the follow-
ing precautions be taken for safe operation:
1. Operate the amplifier from AC mains of
not more than 10% above or below the
_
selected
line
voltage
and
within
the
specified line frequency (50-60 Hz). Fail-
ure to comply with these limits will in-
validate the warranty.
2. When using input sources of uncertain
level or any components which have not
previously been used with your ampli-
fier, always begin with the level controls
at a minimum and gradually increase
them while monitoring the output.
3. Operate the amplifier with the correct
fuses (F1I&F2 = 20 A, F3 = V2 A for 100
or
120
VAC;
F1&F2=10A,F3=
V/4A
for
200,
220
or
240
VAC).
Turn
the
am-
plifier off i i
before replacing the fuses.
4.
Do
not
expose
the
amplifier
to
corrosive
chemicals
such
as
soft
drinks,
lye,
salt
water, etc.
5.
Do
not
tamper
with
the
circuitry.
Circuit
changes
made
by
unauthorized
person-
nel, or unauthorized circuit modifica-
tions, will invalidate the warranty.
AN CAUTION
Do not operate Model 7550 In a
small sealed chamber of any
kind. Improper operation and
overheating will result.
3.2. Functions
The
operating
functions
of
Model
7550
are
shown
and
explained
with
captioned
call-outs
on
the
following
two
pages
(Illustrations
3-1
and
3-2).
A
two-position
power
switch
and
an
amber
LED
power-on
indicator
are
located
on
the
front
panel.
Independent
level
controls
are
located
on
the
front
panel.
Both
level
controls
are
used
in
DUAL
mode,
but
only
the
Channel
1
control
should
be
used
in
MONO
mode.
They
are
used
to
adjust
the
desired
output
level.
There
are
red
JOC
(Input/Output
Comparator)
indicator
LEDs
located
in
the
middle
of
the
front
panel.
They
will
illuminate
whenever
the
distortion
specifications
of
the
amplifier
are
being
exceeded.
The
green
Signal
Presence
LEDs
are
located
on
the
front
panel
just
below
the
JOC
LEDs.
They
illuminate
any
time
there
is
more
than
0.6
Vrms
at
the
output
of
the
amplifier.
There
are
yellow
LEDs
just
below
the
green
LEDs.
They
illuminate
anytime
either
channel
is
in
the
standby
state.
(Continued on page 3-4)
3-1
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a
Operation

TECHRON, 7550 Power Supply Amplifler
Rev. 0
Illustration 3—1 Front Panel Functions
A. Level!
The
volume
of
each
channel
is
independently
controlled
by
these
level
controls.
Each
con-
trol
has
thirty-one
detents
for
accurate
in-
crementation.
The
control
for
Channel
2
should
be
turned
down
(fully
counter
eloek-
wise)
and
not
used
when
operating
in
MONO
mode.
B. 10C®
Ared
Input/Output
Comparator
LED
is
pro-
vided
for
each
channel.
It
illuminates
when
distortion
of
any
kind
exceeds
0.05%.
It
also
acts
as
a
standby
indicator,
illuminating
when
in
STANDBY
mode.
It
is
normal
for
the
JOC
indicators
to
illuminate
briefly
when
the
amplifier
is
turned
on
or
off.
C. Signal Presence
Agreen
LED
is
provided
for
each
channel
to
indicate
when
a
signal
is
present.
Normally
they
will
either
flash
or
stay
illuminated
(de-
pending
on
the
signal
level).
If
the
level
is
very
low
they
may
not
illuminate
at
all.
D. Standby Indicators
Yellow
LEDs
illuminate
when
either
chan-
nel
is
in
the
standby
state.
This
will
occur
when
using
the
DELAY
feature.
E. Power Indicator
An
amber
LED
will
illuminate
whenever
the
Model
7550
is
switched
on.
F. Power
This
two-position
switch
turns
the
amplifier
ON
or
OFF.
At
turn-on,
the
output
is
muted
(placed
in
STANDBY
mode)
for
about
four
seconds
to
protect
your
load
from
start-up
transients.
(This
feature
can
be
disabled
with
the
Delay
Switch
on
the
back
panel.)
G. Fan Intake
The
7550
has
a
dust
filter
on
the
air
intake
to
the
cooling
system.
The
filter
may
be
re-
moved
for
cleaning.
3-2
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Operation

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Illustration 3-2 Back Panel Functions
H. Ground Barrier Strip
Isolation of chassis ground from signal ground
is easily accomplished by removing the shorting
strap from this terminal strip. This may help
remove any hum problems caused by “ground
loops.” (The grounds are always connected in-
ternally with a resistance of 2.7 ohms.)
I. Power Cord
A standard three-wire (grounded) AC cord is
provided. Plug into the specified AC power (see
Section 2.3.5.).
J. input BNC Jacks
An unbalanced BNC jack is provided at the in-
put of each channel. Do not use the input jack
for Channel 2 when in MONO mode.
K. Dual-Mono Switch
Slide this switch left for DUAL mode and right
for MONO mode. In MONO mode the input and
level control for Channel 2 should not be used.
> Only balanced (ungrounded) loads should be
connected to the output jacks. (See Section 2.3.)
L. Low Frequency Protect Switch
Engaging this switch causes the unit to cy-
cle
through
the
“STANDBY”
mode
if
low
fre-
quency (DC-10 Hz) appears at the output.
M. Delay Switch
This
switch
activates
a
four-second
delay
in
the
transition
state
from
“turn-on”
to
high-
voltage
power
supplies
on.
N. Output Connectors
Banana
jacks
are
provided
at
the
output
of
each
channel.
Only
the
two
top
jacks
(red)
are
used
in
MONO
mode
since
both
chan-
nels
are
bridged.
O.
Balanced
Input
Module
Socket
This
11-pin
radial
socket
is
provided
for
one
of
two
optional
balanced
input
modules
(75A06
or
75A07).
The
75A07
uses
a
trans-
former
to
balance
the
inputs
while
the
75A06
uses
active
circuitry.
If
one
of
these
modules
is
used,
the
unbalanced
inputs
should
not
be
used.
3-3
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Operation

TECHRONz 7550 Power Supply Amplifier
Rev.0
On the back panel the Model 7550 has a dust
filter on the air intake to the cooling system.
The filter may be removed for cleaning.
To isolate chassis ground from signal ground,
you can use the back panel Ground Barrier
Strip by removing the shorting strap. Grounds
are always connected internally with the resis-
tance of 2.7 ohms.
The two BNC connectors on the back panel pro-
vide
for
easy
connection
and
disconnection
of
input signals.
Switch
between
DUAL
and
MONO
mode
with
the
Dual/Mono
switch
located
on
the
back
panel.
Below
this
switch,
is
the
Low
Frequency
Pro-
tect
Switch.
Engaging
it
causes
the
unit
to
cy-
cle
through
the
“STANDBY”
mode
when
low
frequency
(DC-10
Hz)
appears
at
the
output.
The
next
switch
is
the
Delay
Switch.
This
switch
activates
a
four-second
delay
in
the
transition
state
from
“turn-on”
to
high-voltage
power
supplies
on.
Model
7550
includes
two
standard
MDP
“dual
banana’
type
output
jacks
on
the
back
panel.
In
DUAL
channel
operation,
use
two
dual
banana
plugs
connected
vertically.
Use
one
dual
ba-
nana
plug
connected
horizontally
to
both
“hot”
(+)
terminals
in
MONO
operation.
The
back
panel
also
includes
an
11-pin
acces-
sory
socket.
Some
accessories
are
described
in
Section
6.
Contact
Techron
engineering
for
any
other
accessories
available.
Each
accessory
comes
with
its
own
documentation
for
installa-
tion
and
use.
Also
located
on
the
back
panel
is
a
heavy
duty
three-wire
(grounded)
AC
line
cord.
3.3. Protection
Techron power amplifiers are widely known for ~
their quality construction, high reliability and
extensive internal protection circuitry. The
Model 7550 is no exception. It is protected
against all the common hazards which plague
high-powered amplifiers such as:
e input overload damage;
e shorted, open and mismatched loads
(oad impedance too low);
chain destruction phenomena;
high frequency overload blowups;
excessive temperature; and,
overloaded power supplies.
eeee
The input stage is protected against excessive
input
signal
level
(overdrive)
by
a
series-limit-
ing resistor.
Protection
against
shorted
and
low
impedance
loads
is
provided
by
a
fast-acting
limiter
circuit
which
instantaneously
limits
the
output
power
to
a
maximum
safe
stress
value.
It
functions
automatically
as
a
current
limiter
at
audio
frequencies
whose
current
limiting
threshold
is
dependent
on
the
history
of
the
output
signal.
Increased
output
current
causes
the
threshold
to
increase,
however,
the
no-signal
threshold
is
high
enough
to
allow
tone
bursting
(even
into
4
ohms)
without
premature
limiting.
Since
the
limiter
has
no
instantaneous
re-
sponse
to
output
voltage,
“flyback”
transients
do
not
appear
in
the
output
when
limiting
oc-
curs
on
inductive
loads.
(“Flyback”
transients
are
a
normal
by-product
of
VI
limiting
with
an
inductive
load.)
Because
the
current
limiter
of
the
Model
7550
will
not yield
to
the
constant
current
demands
of
an
inductive
load,
it
is
immune
to
“flyback”
distortion.
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Operation