ORTEC 556 Service manual

Model 556
High Voltage Power Supply
Operating and Service Manual
WARNING
This equipment generates, uses and can radiate radio frequency energy, and if not
installed and used in accordance with the instruction manual, may cause interference
to radio communications. As temporarily permitted by regulation it has not been tested
for compliance with limits for Class A computing devices pursuant to Subpart J of
Part 15 of FCC Rules, which are designed to provide reasonable protection against such
interference. Operation of this equipment in a residential area is likely to cause
interference, in which case the user, at his own expense, will be required to make
whatever measures may be required to correct the interference.
Printed in U.S.A. ORTEC
®
Part No. 628430 0813
Manual Revision K

ii
Advanced Measurement Technology, Inc.
a/k/a/ ORTEC
®
, a subsidiary of AMETEK
®
, Inc.
WARRANTY
ORTEC* warrants that the items will be delivered free from defects in material or workmanship. ORTEC makes
no other warranties, express or implied, and specifically NO WARRANTY OF MERCHANTABILITY OR FITNESS
FOR A PARTICULAR PURPOSE.
ORTEC’s exclusive liability is limited to repairing or replacing at ORTEC’s option, items found by ORTEC to be
defective in workmanship or materials within one year from the date of delivery. ORTEC’s liability on any claim
of any kind, including negligence, loss, or damages arising out of, connected with, or from the performance or
breach thereof, or from the manufacture, sale, delivery, resale, repair, or use of any item or services covered by
this agreement or purchase order, shall in no case exceed the price allocable to the item or service furnished or
any part thereof that gives rise to the claim. In the event ORTEC fails to manufacture or deliver items called for
in this agreement or purchase order, ORTEC’s exclusive liability and buyer’s exclusive remedy shall be release
of the buyer from the obligation to pay the purchase price. In no event shall ORTEC be liable for special or
consequential damages.
Quality Control
Before being approved for shipment, each ORTEC instrument must pass a stringent set of quality control tests
designed to expose any flaws in materials or workmanship. Permanent records of these tests are maintained for
use in warranty repair and as a source of statistical information for design improvements.
Repair Service
If it becomes necessary to return this instrument for repair, it is essential that Customer Services be contacted
in advance of its return so that a Return Authorization Number can be assigned to the unit. Also, ORTEC must
be informed, either in writing, by telephone [[phone]] or by facsimile transmission [[phone]], of the
nature of the fault of the instrument being returned and of the model, serial, and revision ("Rev" on rear panel)
numbers. Failure to do so may cause unnecessary delays in getting the unit repaired. The ORTEC standard
procedure requires that instruments returned for repair pass the same quality control tests that are used for
new-production instruments. Instruments that are returned should be packed so that they will withstand normal
transit handling and must be shipped PREPAID via Air Parcel Post or United Parcel Service to the designated
ORTEC repair center. The address label and the package should include the Return Authorization Number
assigned. Instruments being returned that are damaged in transit due to inadequate packing will be repaired at
the sender's expense, and it will be the sender's responsibility to make claim with the shipper. Instruments not
in warranty should follow the same procedure and ORTEC will provide a quotation.
Damage in Transit
Shipments should be examined immediately upon receipt for evidence of external or concealed damage. The
carrier making delivery should be notified immediately of any such damage, since the carrier is normally liable
for damage in shipment. Packing materials, waybills, and other such documentation should be preserved in order
to establish claims. After such notification to the carrier, please notify ORTEC of the circumstances so that
assistance can be provided in making damage claims and in providing replacement equipment, if necessary.
Copyright © 2013, Advanced Measurement Technology, Inc. All rights reserved.
*ORTEC
®
is a registered trademark of Advanced Measurement Technology, Inc. All other trademarks used herein are
the property of their respective owners.

iii
CONTENTS
SAFETY INSTRUCTIONS AND SYMBOLS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iv
SAFETY WARNINGS AND CLEANING INSTRUCTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iv
1. DESCRIPTION ...................................................................... 2
2. SPECIFICATIONS ................................................................... 2
2.1. PERFORMANCE .............................................................. 2
2.2. CONTROLS .................................................................. 2
2.3. INPUTS ...................................................................... 3
2.4. OUTPUTS .................................................................... 3
2.5. INDICATOR .................................................................. 3
2.6. ELECTRICAL AND MECHANICAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.7. ACCESSORIESAVAILABLE ..................................................... 3
2.8. RELATEDEQUIPMENT ......................................................... 3
3. INSTALLATION...................................................................... 4
3.1. GENERAL ................................................................... 4
3.2. CONNECTIONTOPOWER ...................................................... 4
3.3. CONNECTING INTO A SYSTEM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.4. CONNECTING AN EXTERNAL REFERENCE INPUT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. CIRCUITDESCRIPTION .............................................................. 5
5. MAINTENANCE AND TROUBLESHOOTING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
5.1. GENERAL .................................................................... 6
5.2. TROUBLESHOOTING SUGGESTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

iv
DANGER Opening the cover of this instrument is likely to expose dangerous
voltages. Disconnect the instrument from all voltage sources while it is
being opened.
WARNING Using this instrument in a manner not specified by the manufacturer may
impair the protection provided by the instrument.
CAUTION To prevent moisture inside of the instrument during external cleaning,
use only enough liquid to dampen the cloth or applicator.
SAFETY INSTRUCTIONS AND SYMBOLS
This manual contains up to three levels of safety instructions that must be observed in order to avoid personal
injury and/or damage to equipment or other property. These are:
DANGER Indicates a hazard that could result in death or serious bodily harm if the safety instruction is
not observed.
WARNING Indicates a hazard that could result in bodily harm if the safety instruction is not observed.
CAUTION Indicates a hazard that could result in property damage if the safety instruction is not
observed.
Please read all safety instructions carefully and make sure you understand them fully before attempting to
use this product. In addition, the following symbol may appear on the product:
ATTENTION – Refer to Manual
DANGER – High Voltage
Please read all safety instructions carefully and make sure you understand them fully before attempting to
use this product.
SAFETY WARNINGS AND CLEANING INSTRUCTIONS
Cleaning Instructions
To clean the instrument exterior:
!Unplug the instrument from the ac power supply.
!Remove loose dust on the outside of the instrument with a lint-free cloth.
!Remove remaining dirt with a lint-free cloth dampened in a general-purpose detergent and water solution.
Do not use abrasive cleaners.
!Allow the instrument to dry completely before reconnecting it to the power source.

v

vi

1
THIS INSTRUMENT PRODUCES EXTREMELY HAZARDOUS VOLTAGES AT A
POTENTIALLY LETHAL CURRENT LEVEL. NEVER CONNECT OR DISCONNECT
THE HIGH VOLTAGE OUTPUT CONNECTOR WITH THE POWER SWITCH ON.
NEVER CHANGE THE OUTPUT POLARITY SWITCH WITH THE POWER SWITCH ON.
ALWAYS SWITCH POWER OFF AND WAIT AT LEAST 30 SECONDS BEFORE
CONNECTING OR DISCONNECTING CABLES AND BEFORE CHANGING THE
OUTPUT POLARITY.
ORTEC MODEL 556
HIGH VOLTAGE POWER SUPPLY
1. DESCRIPTION
The ORTEC Model 556 High Voltage Power Supply
is a standard double-width NIM module that
provides either polarity of output voltage from 50 V
to 3000 V, 0 to 10 mA. The adjusted output voltage
of the selected polarity is available simultaneously
through two SHV rear-panel connectors. A rear-
panel slide switch permits operation on either 115 V
or 230 V ac input power, furnished through a
removable power line cord and connector.
The Model 556 features a front-panel LCD meter
which can be programmed via a front-panel toggle
switch to display either output voltage or load
current. The output voltage can be programmed by
an external control via a rear-panel BNC connector.
The Model 556 provides the extremely stable, low-
noise, high voltage that is required for proper bias of
photomultiplier tubes, ionization chambers, and
semiconductor detectors.
DANGER
2. SPECIFICATIONS
2.1. PERFORMANCE
OUTPUT POLARITY Positive or negative, selected
by switch on rear panel.
OUTPUT RANGE 50 to 3000 V; minimum usable
voltage 10 V.
OUTPUT LOAD CAPACITY 0to 10 mA.
REGULATION <0.0025% variation in output
voltage for combined line and load variations within
operating range at constant ambient temperature.
TEMPERATURE INSTABILITY <±50 ppm/EC after
30 min warmup; operating range 0 to 50EC.
LONG-TERM DRIFT <0.01%/hour and <0.03% per
24 hr variation in output voltage at constant input
line voltage, load, and ambient temperature after
30 min warmup.
OUTPUT RIPPLE 15 mV peak-to-peak, 20 Hz to
20 MHZ.
OVERLOAD PROTECTION Internal circuitry
protects against overloads including short circuits.
RESETTABILITY Output voltage can be reset to
within 0.1%.
2.2. CONTROLS
POWER Front-panel switch energizes unit when
power cord is connected to appropriate source, and
an adjacent red LED lamp indicates when power is

2
applied.
OUTPUT LEVEL One 6-position switch, one
5-position switch, and one 10-turn precision
potentiometer; output level is the sum of
the 3 settings.
METER Front-panel switch selects display of output
voltage in kV or load current in mA.
POLARITY Rear-panel switch selects either
positive or negative output polarity.
CONTROL Rear-panel locking switch selects the
reference source for the output voltage.
!
!!
!lnt Selects the internal reference source; the
front-panel controls select the output amplitude.
!
!!
!Ext Selects the external reference source;
output voltage is proportional to magnitude of
reference input.
AC VOLTAGE Rear-panel slide switch selects
either 115 V or 230 V ac input voltage.
2.3. INPUTS
AC POWER 103–129 V or 206–258 V, 47–63 Hz,
70 W nominal at full output power; supplied through
international standard IEC power connector on rear
panel. Fuse rating: 1.5 A (FAST) (250V) size 3AG
for 115V or 0.75A(F) (250V) size 5×20 mm for 230V
ac operation.
EXTERNAL CONTROL Full range of output
voltage can be based on an external dc reference
level furnished through a rear-panel BNC connector;
control voltage range is 0 through ±6.9 V dc; control
voltage polarity must be the same polarity as that
selected by the rear-panel Polarity switch; this input
protected against over-voltages >±7 V. Input imped-
ance >45 kΩ.
2.4. OUTPUTS
REGULATED DC OUTPUT The adjusted and
regulated voltage, with selected polarity, is furnished
simultaneously to the two SHV connectors on the
rear panel.
2.5. INDICATOR
METER Front-panel LCD display indicates output
voltage in kV ±10 V or load current in mA ±10 µA.
Load current is sum of external load current and
internal load current. Internal load resistance is
-5 MΩ.
2.6. ELECTRICAL AND MECHANICAL
POWER REQUIREMENTS 115 or 230 V ac,
47–63 Hz, 70 W nominally.
WEIGHT
!
!!
!Net 3.6 kg (8 lb)
!
!!
!Shipping 4.5 kg (10 lb)
DIMENSIONS Standard double-width NIM module,
per DOE/ER-0457T.
2.7. ACCESSORIES AVAILABLE
Two 3.66 m (12 ft) adapter cables are available from
ORTEC for connecting to the Model 556 SHV output
connectors:
1. ORTEC C-34-12 cable assembly: RG-59 A/U
(75 Ω) cable with one C-37 SHV female plug and
one C-26 MHV male plug.
2. ORTEC C-36-12 cable assembly: RG-59 A/U
(75 Ω) cable with two C-37 SHV female plugs.
2.8. RELATED EQUIPMENT
Each of the two outputs of the Model 556 can be
used as a power source for any application that is
within the operating limits of the power supply. Both
output levels are identical and of the same polarity.
The load on the Model 556 output circuit is the sum
of the individual loads connected to the output
connectors, and the load current can be monitored
by the front panel LCD meter.
This power supply is ideal for use with either one
detector or a pair of detectors where the voltage
level requirements are the same for both detectors.
The appropriate types of detectors for which the
Model 556 is designed include photomultiplier tubes,
ionization chambers, and semiconductor detectors.

3
3. INSTALLATION
3.1. GENERAL
The Model 556 is normally used in conjunction with
other modular electronics and may be installed in a
standard NIM bin such as an ORTEC Model 4001A.
Since the bin may be rack mounted, any high
temperature equipment that may be installed in the
same rack as the bin must be sufficiently cooled by
circulating air to prevent exceeding the +50EC
(120EF) maximum operating temperature of the 556.
The ORTEC M127/N NIM Fan is available for
forced-air cooling of a rack of equipment.
3.2. CONNECTION TO POWER
The Model 556 requires a grounded ac-power
source of nominal 115 V ac or 230 V ac. A rear
panel international-standard IEC connector allows
the connection of many different types of line cords
between the ac outlet and the 556. A rear-panel
slide switch allows the choice of 115 V ac or
230 V ac input voltages. The 556 is shipped with a
choice of two fuse holder caps to accommodate
either 3AG or 5×20 mm size fuses. On 115 V ac
operation a 1.5 A (FAST) (250V) size 3AG fuse
should be used; on 230 V ac operation, a 0.75A(F)
(250V) size 5×20 mm fuse should be used.
This power supply may be operated entirely
removed from the 4001A bin if desired, since it is
totally self-contained and requires no dc-operating
power levels from the NIM bin. However,
precautions should be taken to ensure that
personnel is aware of the shock hazard at the rear
connectors, and that air space should be provided at
the top and bottom of the instrument.
3.3. CONNECTING INTO A SYSTEM
1. Check to see that the power switch is in the Off
position.
2. Check rear panel 115/230 V ac switch and set to
appropriate position.
3. Install a 1.5 A, 250 V fuse for 115 V ac setting or
a 0.75 A, 250 V fuse for 230 V ac setting in the
rear-panel-mounted fuse holder.
4. Check the polarity switch on the rear panel and
set it for either positive or negative output
polarity as required for the application.
5. Connect a high-voltage cable from either output
connector on the 556 to the instrument to be
powered. Use the other output connector if a
second instrument is to be operated at the same
output voltage.
6. Set the front-panel selector switches and
potentiometer for the desired voltage level. This
is normally specified for the instruments to
which the voltage is to be applied. The adjusted
output voltage will be the sum of the settings of
all three controls.
7. Turn on the power with the switch on the front
panel. The indicator lamp next to the switch will
light to show that input power is being applied.
The indicating meter at the top of the front panel
will also indicate the polarity and amplitude of
either the 556 output voltage or load current,
depending on the setting of the meter switch.
3.4. CONNECTING AN EXTERNAL
REFERENCE INPUT
The Model 556 output voltage level can be
controlled by an external reference level that is
furnished through the rear-panel BNC connector
when the Control locking switch is set at Ext. The
range of input voltage is 0 to 6.9 V to provide an
output from 0 to 3000 V. The front- panel voltage
level controls are ineffective for external reference
operation.
For positive output the polarity selector switch on the
rear panel is set at Pos, and the external reference
should be positive. For negative output the polarity
switch is set at Neg and the external reference
should be negative. The external reference voltage
should be stable and filtered since the output is
linearly proportional to this reference. The external
reference should be capable of driving the 45 kΩ
input impedance.

4
4. CIRCUIT DESCRIPTION
Figure 2 is a simplified block diagram of the Model
556 circuits.
The 556 requires an ac power input, regardless of
the use of an internal or external reference level.
The selected reference level is applied to a precision
regulator and controls the low voltage input level to
an internal 24-kHz oscillator. The oscillator output
voltage is stepped up for the high voltage output
through a converter transformer, and this signal is
rectified and filtered to produce the output to each
output connector.
The front panel meter (M1) is connected to the
output connectors through R65, R85, and R66 when
monitoring output voltage. R66 is used to calibrate
the front-panel display meter. In the load current
display mode, the output ground return current is
sensed by R69. The sensed voltage is inverted by
S7 and fed to meter M1.
Two feedback loops, one for preregulation and one
for output regulation, operate simultaneously. To
maintain the output voltage at a constant voltage,
U1 compares the sampled output voltage against
the reference voltage appearing at its input
terminals. The resulting error signal is amplified by
U2, Q1, and Q5. The output (emitter) of Q5 feeds
the input of the high frequency dc-to-dc converter.
The converter is made up of a free-running oscillator
(Q6-9) driving chopper MOSFETs Q10 and Q11,
which alternately switch on to transfer energy
through high-voltage transformer T2. The converter
output consists of the rectified, filtered, and doubled
high voltage at C17. R53 and C18 further filter the
output voltage.
A preregulator circuit is necessary to limit the power
dissipation by Q5. Therefore its collector and emitter
voltages are compared at U3(5 and 6). The resulting
output represents a request for more Q5 collector
voltage.
U3(1) is synchronized with the power line frequency.
This signal clocks JK flip-flop U4 and when U3(7) is
high, SCR Q12 is fired in synchronization with the
power line through Q2, Q3, and D8. When SCR Q12
fires, current flows through R3 and C1, boosting the
collector voltage at Q5.
Current limiting transistor Q4 monitors the current
through R4 and prevents damage during output
overload by conducting current away from the base
of Q5. Also, if a high voltage output should become
shorted to ground, transistors Q14 and Q15 will
conduct current away from the base of Q5. Current
Fig. 2. Model 556 Block Diagram.

5
pulses in the ground return path during a short
circuit condition produce voltage pulses across R69
which are of sufficient amplitude to turn either Q14
or Q15 On, depending upon the setting of the
POLARITY switch (R.P.). Q15 will become active if
the switch is set for POS and Q14 will be active if
the switch is in the NEG position. Regulators U5 and
U6 provide the necessary internal ±12 V power to
operate the control circuitry, the reference circuit,
and the oscillator.
5. MAINTENANCE AND TROUBLESHOOTING
5.1. GENERAL
The Model 556 should not require maintenance
other than cleaning to prevent leakage paths from
being created by dust collection. If an apparent
malfunction is noted, it is important to determine if it
is within the 556 power supply by disconnecting it
from its load and performing routine diagnostic tests.
The 556 is short-circuit protected, and with a short-
circuit load the output voltage will drop to zero. If an
external short circuit has been applied to the output,
the short circuit must be removed before the 556 will
again produce its adjusted voltage.
5.2. TROUBLESHOOTING SUGGESTIONS
Only service technicians trained and experienced in
the service of high-voltage circuitry should attempt
trouble-shooting this unit. EXTREMELY
DANGEROUS VOLTAGE LEVELS ARE PRESENT
INSIDE THE 556 CHASSIS! OBSERVE GREAT
CAUTION WHEN ANY PROTECTIVE COVERS
ARE REMOVED WITH POWER APPLIED!
To troubleshoot the 556, check the internal ±12 V
supplies first, then check for symmetrical conduction
times for oscillator output MOSFETs Q10 and Q11.
With the 556 set for, positive polarity, the voltages at
U1 (2 and 3) should be nearly identical and equal to
the reference voltage setting. If this is not the case,
check components through the two regulating
feedback loops described in Section 4.

6
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