Oxford Instruments TC948 User manual

INSTRUCTION
MANUAL
TC948
HIGH VOLTAGE
POWER SUPPLY
N94
8MOOFO1

E
E
E
[
E
E
E
E
E
1
E
E
E
E
E

WARRANTY
Oxford
lnstrumeflts
mc
warrants that
the products
or
components
manufactured
by
it
shatl
be
free
from
defects
in
material
or
workmanship
for
a
period
of
one
year
from
the date
of
deiivery to
purchaser.
If
such
product
or
component
is
determined
to
be
defective by
Oxford
instruments
mc, its
sole
warranty
obligation
shali be
imited
to either
replacing
or
repairing
such
defective product
or
component
or
allowing
credit,
at
Oxford’s
option.
Such
warranty
is
further
conditional
upon
the
purchaser
giving
prompt
notice
of
any
such
defect
and
satisfactory
proof
thereof
to
Oxford’s
Customer
Service
Manager.
Thereafter
upon
Oxford’s
approval,
the
purchaser
shali
return
such detective
product
or
component
to
Oxford’s
factory
at
Oak
Ridge,
Tennessee,
ali
transportation charges
prepaid.
Oxford
shall
be
responsibie
oniy
for
transportation
charges
incurred
in
returning
such
product
or
component
to
purchaser.
Ali customs,
brokerage
and duty
charges
shall
be
at
the
expense
of
the
purchaser.
Damage
in
transit
due to
inadequate
packaging
will
be
repaired
at
the
purchaser’s
expense.
Any repairs
or
replacements
by
the
purchaser
without
Oxford’s
approval,
any
willful
abuse
or
any
evidence
that
the
product
or
component was
not
properly used
and maintained
would automaticaHy
void
this
warranty.
Oxford
Instruments
mc
makes
no
warranty
whatsoever
in
respect
to
products
or
components
not
manufactured
by
it,
but
instead,
the
applicabie
warranties,
if
any,
of
the respective
manufacture
thereof
shali
apply.
Likewise
fuses,
batteries,
and
field effect
transistors
in
iow-noise
preamplifiers are
specifically
excluded
from
this warranty.
THIS
WARRANTY
IS
IN
LIEU
OF
ALL
OTHER
WARRANTIES, EXPRESSED
OR
IMPLIED,
STATUTORY
OR
OTHERWISE,
INCLUDING
WARRANTY
OF
MERCHANTABILITY AND
FITNESS.

r
CD
r
rrr
r
rr r r

Section
TABLE
OF CONTENTS
P
age
1.0
INTRODUCTION
2.0
SPECIFICATIONS
2.1
PERFORMANCE
2.2
CONTROLS,
CONNECTORS
AND
DISPLAYS.
2.3
GENERAL
INFOR’tATI0N
3.0
FIRST-TIME
OPERATION
4.0
CIRCUIT
DESCRIPTION
5.0 SERVICING
5.1
GENERAL
SERVICING
INSTRUCTIONS
5.2
FREQUENCY
ADJUSTMENT
5.3
OLfTPUT
VOLTAGE
CALIBRATION
.
6.0 SHIPPING
DAMAGE
7.0
WARRANTY
1 1 1 1 2 2 2 3 3 3 4 4 4
Figure
TABLE OF
FIGURES
P
age
Figure
1
TC 94$
Cal ibration
points
4

E
E
[
E
E
E
[1
E
E
E
E
E
E
E
E
E
E
E

TC 948
HIGH VOLTAGE
SUPPLY
L
TÇNNEEC
..,i
TC 948 -
HIGH
VOLTAGE
SuPPLY
OUTPUI
VOtIAGI
LI’,
300V
3’
DILI IIAOING
1
O
1 DLIII
.
41014
VOt1AGI
.
U 0
‘,lOtlAOt
ON
LRIA
044
TENNEL
EC
_______________
INC.
PHONE
615-483-8405 TWX 810-572-1018
Represented
throughout the
world, TENNELEC,
Iiic.
designs
and
manufactures
state-of-the-art
electronics
for
lhe
consumer,
medical,
research and industrial markels. Inquires about
any
of lhe
varlety of
producls
and services available
from TENNELEC should
be
addtessed
to
TENNELEC,
mc.,
601 Turnpike, Oak
Ridge, Tennessee
37830, USA.

1.0
INTRODUCTION
TENNELEC’s
TC
948
High-Voltage
Suppiy
is
designed
to
furnish
high
current
and
high-voltage
for
scintillation
detectors
in
a
minimum
of
bin
space.
The
out
put is
continously
adjustable
from 50V
to +1500V
with
a
current
of
O
to
imA.
Packaged
in
a
single
width
NIM
module,
the
TC
948
can
be
used
with
the
appro
priate
modules
to
forn
either
a
dual
isotope
counting
system
or
a
dual
detector
system
in
a
portable,
six-wide
minibin.
Automatic
fault
protection
against
overioads,
arcing
and
short
circuits
is
provided.
A
front-panel
lamp
indicates
if
the
protection
circuits
have been
activated.
The
unit
is
powered
completeiy
from
the bin.
2.0
SPECIFICATIONS
2.1
PERFORMANCE
Output:
Continuously
adjustabie
between
+50
and
+1500V
with
a
curtent
range
of
O
to
UM.
Ripple
and
Noise:
Less
than
iOmV
peak-to-peak
to 50
MHz.
Stabiiity:
Less
than
0.01%
drift
in
output
vo]tage
per hour
measured
under
constant
load,
une
voltage,
and
ambient
temperature
after
warm-up.
Resolution:
Better
than
1V.
Resettability
is
0.03%
or
3V
(whichever
is
greater).
The calibration
accuracy
is
better
than
1%
of
the
maximum
output
voltage
setting.
Temperature
Coefficient:
looppm
or
0.0l%/°C
change
in
output
voitage
after
warm-up
over the
00
to
50°C
operating
temperature
range.
2.2
CONTROLS,
CONNECTORS
AND
DISPLAYS
Voltage
Control:
Calibrated
ten-turn
dial
permits
setting
of
the
output
voltage
over
the
50
to
1500V
range.
High-Voltage
Indicator:
Front-panel
]amp
lights
when
the TC
948
is
ON.
Fault
Indicator
Lamp:
Front-panel
iamp
lights
when
the
fault
protection
circuitry
has
been
activated.
It indicates
arcing,
overload
or
short
circuiting.
OFF/ON
Switch:
Front—panei
switch
turns
supply
ON
or
0FF.
When
in
the
ON
position,
the
high-voltage
indicator
lamp
lights.
Output
Connector:
One
SHV
safety
high-voltage
receptacle
on
tear-panei.
Power:
NIM
standard
power
connector.
The TC
94$
requires
+24vdc
@
55mA;
-24vdc
@
7Oma;
+l2vdc
@
l70n;
-l2vdc
@
l6OmA.

—2—
E
2.3
GENERAL
INFORMATION
Packaging: No.
1
NIM
Standard
module.
E
Accessories:
One
instruction
manual.
Net
Weight: 2
ibs
2
ozs
(0.96
Kg).
Shipping
Weight:
5
lbs
2
ozs
(2.33
Kg).
E
Watranty:
One
year.
3.0
FIRST
TIME OPERATION
E
Every
instrument
from
TENNELEC,
mc.
is
thoroughly checked before
it
leaves
the
plant.
However, it is
possible
for
damage
to
occur
during
shipping. Visually
check
the
Model
TC 948
upon
receipt
for possible
external
damage.
If
it
appears
to
be
damaged,
proceed
with
the
instructions
given
in
the
SHIPPING
DAMAGE
section
of
this
manual.
It
is
recommended
that
the
power
supply
of
the
bin
be
0FF
when
the
module
is
inserted.
[
4.0
CIRCUIT DESCRIPTION (See Block
Diagram)
The
TC
948
is
basically
an
operational
amplifier
with
two
major
stages.
[
The
low-voltage
amplifier
is
a
conventional
operational
amplifier.
Q903
is
a
dual
FET
for
good
temperature
stability
and
drift
characteristics,
and
IC
901
is
used
for
the
second
gain
stage
for
the
sarne
reasons.
Q90l
and
Q902
are
the
output
drivers
for the positive
and
negative
outputs,
respectively.
Re
sistors
R3,
R4
and
R5,
R34
are
the
load
resistors
for
Q901
and
Q902.
Sta
bilization
is
accomplished
with
R904,
C90],
Cl,
and
C2.
Diodes
Dl
and
D2
protect
Q903.
The
variable
input
voitage
is
obtained
through
R2
(i0—turn
potentiometer)
from
013.
The
high-voltage amplifier
section
consists
of
a
transformer,
transformer
drivers,
and
voltage
doubler.
Unijunction
Q4
generates
an
approximate
50kHz
spike
which
ciocks
fiip—flop
IC
lA.
The
ouput
of
IC
1 is
two
25kHz
square
waves 180°
out of
phase.
These
square
waves
are
applied
to
Q6
and
Q7
which
drive
Q8
and
Q9
respectiveiy.
Transistors
Q8
and
Q9
drive
the
transformer
17.
Current
is
supplied
to
the
center
tap
of
Ti from
a
White
foliower
stage
consisting of
QiO
and
Qil
. This
is
a
gain-of-one
stage
with high
input
impedance
and
high
output
current
capability.
Power
is
supplied
for
the
White
follower
stage
from
the
Bin.
The
output
of
the
high-voltage
transformer
is
a square
wave
which
is
rectified
by
the
voltage
doubler
made
up
of
07,
08,
Cli,
C12,
C13,
C14,
C25,
and
C26.
The
resulting
dc
output voltage
is
filtered
by C15,
R21,
and C16
and
applied
to the
output
terminais
through
current
limiting resistor
R22.
E
E

-3-
The
high-vo]tage
OFF/0N
Switch
controls power
to
the White
follower
and
shorts
the
J-K
inputs
of
IC
lA
to
ground.
The
fault
lamp
is
driven
from
a
circuit
which
senses
the
suming
junction
of
the
amplifier.
Pin
7
of
the
A900 module
is
a
point
which
looks
at
the
surnrning
junction
after
it has
been
amplified
by
Q903.
In
addition
to the
amplification,
Pin
7
has another
important
feature:
its
voltage
always
goes positive
if
the
suming
junction
breaks
loose
in
either
direction.
This
allows
the
base
of
Qi
to sense
either
undervoltage
or
overvoltage at
the
ouput
of
the supp]y
by
looking
at
Pin
7.
This
is
an
important
feature
because
many
internal
fai]
ures
in the
power
supply
will
cause
the
output voltage
to
go
to
fuli
scale
and
this
can damage
detectors.
If
the voltage
at
the
base
of
Ql
goes
ovet
8.5V (indicating
that
the
sunnling
junction
has
broken
loose),
Q3
turns
on the
FAULT
lamp
and
shorts
the
reset
input
of
IC lA
to
ground,
turning
off IC
lA and
the
transformer
drive.
If
this
happened
as
a
result
of
a short
at
the
output,
the
voltage
will
stay
off
until
the
high-voltage
switch
is
turned
off
and
back
on.
If
the
FAULT
lamp
came
on as
a
result
of
overvoltage (QlO or
Q]1
shorted)
a feedback
loop will
be
set
up
through
Ql
and
Q2, Q3,
and
IC
lA
and the
transformer
drivers.
The
feedback
loop bypasses
the
last
half
of
the
A900
and
QlO
and
Qil
to
contro]
the output
voltage.
If
the power
supp]y
begins
to
draw
excessive
cutrent
from
the
Bin (for
any
reasons),
a
voltage
drop
wil]
be created
across
R28
and
R29.
This
will
turn
on Ql2.
When
Q12
turns
on,
jt
will
actjvate
IC lB.
This
will
turn
on Q13,
lighting
the
FAULT
lamp
and
removing
the
transformer
drive,
thus
disabling
the
module.
The
circuit
wj]l
stay
in this
condition
until
the
HIGH-VOLTAGE
switch
is
turned
0FF,
which
resets
the
IC
lB.
5.0
SERVICING
5.1
GENERAL
SERVICING
INSTRUCTIONS
In the
event of
a
component
failure,
replacement
may
be
done
in the
field
or
the
instrument
may
be
returned to
our
plant
for
repair.
There
will
be
no
charge
for
repairs
that
fail
within
the
warranty.
lHE
TC
948 PRODUCES
VÂHGEROUS
VOLTAGE.
USE
CAUT1ON
lF
YOU
ÁTTEMPT
10
SER VICE
lHE
UtJIT.
5.2
FREQUENCY
ADJUSTMENT
Turn
the
supply
ON and
bting
the
output
voltage
up
to
1.5kV.
Load
the
supply with a
1.5
megohm
2 watt
load.
Using
a
suitable
meter,
monitor
the
voltage
drop
across
P28
(see
Fig.
1).
Adjust
R12
for
the
minimum
voltage
across
R28.

L
E
E
E
E
E
[
E
[
lhe
following
instruments
are
used
at
IENNELEC
for
output
vo]tage
calibration
of
the
TC
948:
1)
An
electrostatic
voltmeter
with
0.5%
accuracy
and
1
x
1015ç2
input
impedance.
[
2)
A
d.c.
differentiai
vo]tmeter
with
an
accuracy
equal
to
±0.01%
of
input
plus
0.001%
of
range
plus
10
.iV.
[
The
high-voitage
output
control
is
ca]ibrated
by
Ri
(see
Fig.
1).
6.0
SHIPPING
DAMAGE
Upon
receipt
of
the
instrument,
examine
it
for
shipping
damage.
Damage
claims
should
be
filed
with
the
carrier.
The claims
agent
shouid
receive
a
fuil
re
port;
a
copy
of
that
report
should
be
sent
to
TENNELEC,
mc.,
P.0.
Box D,
Oak
Ridge,
Tennessee
37830.
lhe
model
number
and
serial
nuntier
of
the
in
strument
must
be
included
in
the
report.
Any
remedial
action
taken
by
TENNELEC,
mc.
will
be
based
on
the information
contained
in
this
report.
7.0
WARRANTY
In
connection
with
TENNELEC’s
warranty
(inside
front
cover),
TENNELEC
suggests
that
if
a
fault
deveiops,
the
customer
should
innediateiy notify
the TENNELEC
Nuclear
Customer
Service
Manager.
He
may
be
able
to
prescribe
repaits
and
to
send
replacement
parts
which
wiil
enable
you
to
get
the
instrument
operating
sooner
and
at
less
expense
than
if
you returned
it.
L
LI
5.3
OUIPUI
VOLIAGE
CALIBRATION
Fig.
1.
TC
948 Calibration
points

—5
Shou]d
return
prove
necessary,
the TENNELEC
Nuclear
Customer
Service
Manager
must
be
informed
either
IN WRITING,
BY CABLE
oe BY TWX
of
the
nature
of
the
fault
and
the model
number and
serial
number
of the
instrument.
Pack
the
instrument
well
and ship
PREPAID
and
INSURED
to TENNELEC,
mc.,
601
Oak
Ridge
Turnpike,
Oak Ridge,
Tennessee
37830.
As
stated in
the warranty
AMAGE
IN
TRANSIT
WILL BE
REPAIRED
AT THE
SENDER’S
EXPENSE
as
will damage
that obviously
resulted
from
abuse
or nisuse
of
the
instrument.
Quotations
for the
repair
of
such
damage
will be
sent for
your approval
before
repair
is undertaken.
5/77
- EngLvee’&i9
and
componeat
£mpn.ove.meivts
may
bc. made
a.tc
da.te
o
pnntn.