Advanced Instruments 3250 User manual

3255SM Rev. 25
The Advanced™ Osmometer 3250
The Advanced™ Cryoscope 4250
Service Manual

2
Copyright Advanced™ Osmometer 3250/Cryoscope 4250 Service Manual
Copyright
This service manual is copyrighted by Advanced Instruments with all rights reserved. Under
copyright laws, this guide may not be reproduced in any form, in whole or part, without the
prior written consent of Advanced Instruments.
© 2019 Advanced Instruments.
Advanced Instruments has reviewed this manual thoroughly. All material contained within is
believed reliable, but the accuracy and completeness are not guaranteed or warranted, and
are not intended to be representations or warranties concerning the product described.
Microsoft® and Windows® are registered trademarks of Microsoft Corporation in the United
States and other countries. Intel® is a registered trademark of Intel Corporation in the United
States and other countries. All other trademarks are the property of Advanced Instruments.
Hot-Line™ Service
If you have any questions or problems regarding the proper operation of your instrument,
please contact our Hot-Line Service department by calling one of the following numbers.
• 800-225-4034 (toll-free within the USA and Canada)
• +US 781-320-9000 (elsewhere)
• 781-320-0811 (fax)
• Email: [e-mail]

3
Copyright .....................................................................................................................................................2
Hot-Line™ Service......................................................................................................................................2
Safe Use ....................................................................................................... 7
Symbol Conventions ................................................................................................................................7
General Cautions .......................................................................................................................................8
Service and Maintenance Cautions ...................................................................................................8
Hazardous Material Cautions ...............................................................................................................9
FCC Requirements ...................................................................................................................................9
Supplies, Parts, and Accessories ..........................................................10
3250 Supplies, Parts, and Accessories ..........................................................................................10
3250 Controls and Calibration Standards ..................................................................................... 11
4250 Supplies, Parts, and Accessories .......................................................................................... 12
4250 Reference Solutions and Calibration Standards............................................................. 12
Chapter 1 Overview .................................................................................. 13
Product Description ............................................................................................................................... 13
The Service Manual ................................................................................................................................ 13
Service Assistance .................................................................................................................................. 13
3250/4250 Components...................................................................................................................... 14
Chapter 2 Calibration ..............................................................................16
Chapter 3 3250/4250 Circuit Description .......................................... 17
Power Supply (Serial Suffix A - C) ...................................................................................................17
Power Supply (Serial Suffix D and Higher) .................................................................................. 18
Front End ................................................................................................................................................... 18
325605 Control Board Set Description ......................................................................................... 18
325620/425620/325621/425621 Processor Board .................................................................... 18
PCB605 Application Board ................................................................................................................ 19
Other Circuit Components .................................................................................................................. 21
Barcode Port Connections ..................................................................................................................22
Chapter 4 Cleaning and Maintenance ................................................24
Flushing the System ............................................................................................................................. 24
Draining the System ............................................................................................................................. 24
Removing the Head Cover and the Instrument Cover ........................................................... 25
Osmometer/Cryoscope Well Cleaning .......................................................................................... 26
Osmometer Well Cleaning ................................................................................................................. 26
Cryoscope Well Cleaning ....................................................................................................................27
Cleaning and Lubricating the Printer (Serial Suffix A - C, only) ........................................ 28
Probe and Stir/Freeze Wire Alignment ........................................................................................ 28
Table of Contents

4
Chapter 5 Troubleshooting ...................................................................30
Introduction .............................................................................................................................................30
Freeze “Buzz” Amplitude ...................................................................................................................30
Stir Driver Noise (Serial Suffix A - C only) ................................................................................... 31
Installation Option A ......................................................................................................................... 32
Installation Option B .........................................................................................................................33
Head Sensor Adjustment .................................................................................................................... 33
Head Up/Down Test ............................................................................................................................. 34
Power On Diagnostics ......................................................................................................................... 35
A/D Tests ............................................................................................................................................... 35
Sample Bin Setting ............................................................................................................................... 36
Block Bin Setting ...................................................................................................................................37
Stir Amplitude ..........................................................................................................................................37
Display/Printer Test ............................................................................................................................... 38
Beeper Test .............................................................................................................................................. 38
Keypad Test .............................................................................................................................................. 38
Barcode Test ............................................................................................................................................ 39
Reset Serial Number ............................................................................................................................. 39
Instrument Software Updates ........................................................................................................... 39
Performing FLASH firmware update .............................................................................................40
Method without opening cover ................................................................................................... 40
Method with cover removed ......................................................................................................... 40
Option Switch Settings ..................................................................................................................... 41
Troubleshooting Table ......................................................................................................................... 42
Chapter 6 Replacement Instructions ..................................................50
Mandrel Replacement 3LH500 ........................................................................................................50
Clapper Replacement 3C2241R ......................................................................................................... 51
Control Board Set Replacement 325605R/425605R ............................................................ 52
Application Board (Only) Replacement PCB605R .................................................................. 53
Processor Board (Only) Replacement325621R/425621R ....................................................... 54
Cooling Assembly Replacement 3D3300R/4D3300R ........................................................... 56
Cooling Fan Replacement 4D3360 ................................................................................................ 58
Display Board Replacement 74051R/702041R ..........................................................................60
Fuse Replacement 70011/70022 ...................................................................................................... 61
Driver Board Replacement PCB523R ............................................................................................ 63
Head Up Relay or Head Down Relay Replacement 3D3109 ................................................ 65
Heat Transfer Fluid Pump Assembly Replacement 4D3690 ............................................... 67
Heat Transfer Fluid Pump Assembly Replacement 4D390 .................................................. 68
Fluid Filter/One-way Check Valve Replacement (4D3710R/4D3705R or 99133R) ...... 71
Keypad Replacement 325511R ...........................................................................................................73
Load Resistor Replacement Instruction ........................................................................................75
Motor Assembly Replacement 4D3350R/325304R .................................................................77
NVRAM Battery Replacement 71027R ........................................................................................... 81
Power Supply Assembly Replacement 4D3950/325950R ................................................... 83
Printer Assembly Replacement 325400R ................................................................................... 86
Printer Assembly Replacement 325420R .................................................................................... 88
325404PM Replacing the Printer Mechanism ............................................................................. 91

5
Probe Alignment Instructions - Alignment Tool 3LA702/Alignment Toolkit 3LA700 93
Sample Probe Replacement 3D3700 ............................................................................................ 98
Cryoscope Sample Probe Versions FAQ .................................................................................... 100
Stir/Freeze Coil Replacement 3D2404R .....................................................................................102
Stir/Freeze Wire Replacement 3LH243/4LH243 .................................................................... 104
PCB520 Transistor Replacement Instruction 35010 to PCB520R Substitution ..........105
PCB522 Transistor Replacement Instruction 35050 to PCB522R Substitution ......... 108
Tube Ejector Spring Replacement 3D3312R/4D3312 ...............................................................111
Yoke Replacement 3LH230R ............................................................................................................112
Upgrade Kit - 3250/4250 Suffix D to E ........................................................................................113
Chapter 7 Schematics............................................................................ 119
PCB402 Assembly Drawing Rev0 ..................................................................................................119
PCB402 Assembly Drawing Rev1 ...................................................................................................120
PCB402 Printer Interface Board Schematic Rev0 ...................................................................121
PCB402 Printer Interface PCB402 Schematic Rev1 ...............................................................122
PCB523 Assembly Drawing Rev0 .................................................................................................. 123
PCB523 Assembly Drawing Rev4 ..................................................................................................124
PCB523 Driver Board Schematic Rev0 ........................................................................................125
PCB523 Schematic Rev2 ...................................................................................................................126
PCB605 Assembly Drawing Rev 11 ................................................................................................ 127
PCB605 Application Board Schematic Rev2 ............................................................................128
PCB605 Schematic Rev5 ...................................................................................................................129
PCB620 Assembly Drawing .............................................................................................................130
PCB620 Processor Board Schematic Rev4 ................................................................................131
210102 Assembly Drawing Rev1 ...................................................................................................... 132
210102 Schematic Rev1 ....................................................................................................................... 133
3D3380 Assembly Drawing Rev5 ..................................................................................................134
3D3380 Assembly Drawing Rev9 ..................................................................................................135
3D3380 Schematic Rev4 ...................................................................................................................136
3D3380 Schematic Rev5 ................................................................................................................... 137
325000 Interconnection Schematic Rev4 for Serial Suffix A & B .................................... 138
325000 Interconnection Schematic Rev5 for Serial Suffix C ............................................. 139
325000 Interconnection Schematic Rev6 for Serial Suffix C ............................................ 140
325000 Interconnection Schematic Rev6 for Serial Suffix D..............................................141
325000 Interconnection Schematic Rev8 for Serial Suffix D .............................................142
325000 Interconnection Schematic Rev8 for Serial Suffix E .............................................143
325000 Interconnection Schematic Rev11 for Serial Suffix E ............................................. 143
Appendix A Model 3250 Specifications .......................................... 145
Serial Suffix A - C .................................................................................................................................145
Serial Suffix D and Higher. ................................................................................................................147
3250 Design Changes .........................................................................................................................148
Appendix B Model 4250 Specifications .......................................... 149
Serial Suffix A - C .................................................................................................................................149
Serial Suffix D and Higher .................................................................................................................. 151
4250 Design Changes .........................................................................................................................152

6
Appendix C Regulatory Notices .........................................................153
Symbol Conventions ............................................................................................................................153
Symbol Definitions ...............................................................................................................................156
Appendix D Replacement Parts ..........................................................159
Appendix E Product Disposal and Recycling .................................. 161
Appendix F Service Log .......................................................................162

7
Safe Use
To reduce the risk of bodily injury, electric shock, fire, and damage to your instrument,
please read and observe the precautions in this User’s Guide.
• If the product is used in a manner not in accordance with the equipment design,
operating instructions or manufacturer’s recommendations, the operation of the product
may be impaired to the extent that a safety hazard is created.
• Do not attempt to perform electrical work if you are not fully qualified. This manual is not
a substitute for electrical training.
Symbol Conventions
The exclamation point within an equilateral triangle is intended to alert the user to
the presence of important operating and maintenance (servicing) instructions in the
literature accompanying this product.
The lightning flash with arrowhead symbol within an equilateral triangle is intended
to alert the user to the presence of uninsulated dangerous voltage within the
product’s enclosure that may be of sufficient magnitude to constitute risk of electric
shock to persons.
The static symbol within an equilateral triangle is intended to alert the user to the
presence of internal components that could be damaged by static electricity.
This static symbol is intended to alert the user to the presence of a specific
component that could be damaged by static electricity.
This symbol indicates the presence of alternating current (AC).
This symbol indicates the presence of a fuse
This symbol indicates the presence of protective earth ground.
This symbol indicates the power is ON.
This symbol indicates the power is OFF.
Note Additional symbol definitions are available in Symbol Definitions.

8
General Cautions Advanced™ Osmometer 3250/Cryoscope 4250 Service Manual
General Cautions
• This product should be operated only with the type of power source indicated on the
product’s electrical ratings label. Refer to the installation instructions included with the
product.
• If the power cord provided is replaced for any reason or if an alternate cord is used, the
cord must be approved for use in the local country. The power cord must be approved for
the product’s listed operating voltage and be rated at least 20% greater than the ampere
ratings marked on the product’s electrical ratings label. The cord end that connects to the
product must have an IEC 60320 connector.
• Plug the product into an approved grounded electrical outlet.
• Do not disable the power cord’s grounding pin.
• If an extension cord or power strip is used, make sure that the cord or strip is rated for
the product, and that the total ampere ratings of all products plugged into the extension
cord or strip do not exceed 80% of the cord’s or strip’s rating limit.
• Route power cords so that they will not be walked on, tripped on, or pinched by items
placed upon or against them. Pay particular attention to the plug, electrical outlet, and
the point where the cord exits the product.
• Do not pull on cords and cables. When unplugging cords or cables, grasp the
corresponding connector.
• Do not install or use this product in any area subject to extreme short-term temperature
variations, or locations that exceed the specified operating environment temperatures.
• Never use this product in a wet area.
• To avoid injury or fire hazard, do not operate this product in an explosive atmosphere.
• Do not install or use the product on an unstable, non-level work surface.
• Do not operate this product with the covers removed or unsecured.
Service and Maintenance Cautions
• Unplug the power cord prior to opening or removing covers, or else you may be exposed
to electric shock, excessive temperatures, or mechanical hazards.
• Performing service or maintenance not detailed in the User’s Guide, with or without this
Service Manual, should only be done by a qualified service technician.
• Never restrict airflow into or out of the product. Occasionally, check the air vents for
blockage.
• Wipe the exterior of the product with a soft, damp cloth as needed. Using cleaning
products other than those specified, may discolor or damage the finish.
• If the product requires service for any of the following reasons, unplug the product from
the electrical outlet and refer service to a qualified service technician.
• The power cord, extension cord, power strip or power input module is damaged.
• Liquid has been spilled into the interior of the product.
• A foreign object has fallen into the product.
• The product has been dropped or damaged by a falling object.
• There are noticeable signs of overheating or a burning odor.
• The product does not operate normally when you follow the operating procedures.
• The main supply fuse(s) or any internal fuse(s) continually fail.

9
Hazardous Material Cautions
• A discharge of static electricity from contact with the human body or other conductor
may damage system boards or static sensitive devices. Never perform internal
maintenance without following recommended static protection procedures.
• The product is equipped with operator accessible fuses. If a fuse blows, it may be due to
a power surge or failure of a component. Replace the fuse only once. If the fuse blows
a second time, it is probably caused by failure of a component part. If this occurs, refer
service to qualified service personnel. Always replace the fuse with one of the same
rating, voltage, and type. Never replace the fuse with one of a higher current rating.
• When servicing the product, use only factory-specified parts.
• WARNING: When returning this product for service, or shipping this product to a second
location, remove all hazardous specimens and decontaminate the product before
packaging for shipment. If the product cannot be decontaminated, consult with your
shipping agent on appropriate packaging and marking.
Hazardous Material Cautions
• WARNING: Handle all biohazardous materials according to established good laboratory
practices and follow your institution’s exposure control plan. Persons handling human
blood and body fluid samples must be trained in blood-borne hazards and observe
universal precautions. Universal precautions is an approach to infection control,
where all human blood and body fluids are treated as if known to be infectious. Use
personal protective equipment such as gloves, gowns, etc., to prevent exposure. Store
biohazardous materials in regulated waste containers and dispose of these materials
in a safe and acceptable manner that is in compliance with all country, state and local
requirements.
• If a biohazardous material is spilled on or inside the equipment, decontaminate the
equipment using a 1% bleach solution, or as outlined by those policies and procedures
established within your institution.
• To avoid injury or fire hazard, do not operate this product in an explosive atmosphere.
FCC Requirements
WARNING: Changes or modifications to this unit not expressly approved by Advanced
Instruments could void the user’s authority to operate the equipment.
• This equipment has been tested and found to comply with the limits for a Class B
digital device, pursuant to Part 15 of the FCC Rules. These limits are designed to provide
reasonable protection against harmful interference in a residential installation. This
equipment generates, uses, and can radiate radio frequency energy and, if not installed
and used in accordance with the instructions, may cause harmful interference to radio
communications. However, there is no guarantee that interference will not occur in a
particular installation. If this equipment does cause harmful interference to radio or
television reception, which can be determined by turning the equipment off and on, the
user is encouraged to try to correct the interference by one or more of the following
measures:
– Reorient or relocate the receiving antenna.
– Increase the separation between the equipment and receiver.
– Connect the equipment into an outlet on a circuit different from that to which the
receiver is connected.
– Consult the dealer or an experienced radio TV technician for help.

10
Supplies, Parts, and Accessories
To order parts and accessories, contact the Advanced Instruments Customer Service
Department by using one of the following numbers.
• 800-225-4034 (toll-free within the USA and Canada)
• +US 781-320-9000 (elsewhere)
• 781-320-3669 (fax)
3250 Supplies, Parts, and Accessories
Part description Part No.
2-Amp Time Delay (T) Fuse for 100-130V 70022R
Clapper 3C2241
Sample Tubes, Disposable 0.2 or 0.25 mL 3LA825
Heat Transfer Fluid 3DA811
Heat Transfer Fluid Filter 4D3710R
Air Filters (package of 6) 3D2340
Printer Paper (5 rolls) FLA835
Operator/Supervisor Keys 3D3185
Probe/Stir Wire Alignment Tool Kit 3LA700
Replacement Sample Probe with Mandrel and one 10-mL
ampule of Probe Bin Setting Fluid (Stainless Steel)
3D3700
Mandrel 3LH500
One-way Check Valve 4D3705R
Sample Tube Rack 3LA846
RS-232 Cable, 3 meters RS232-CABLE
Service Manual 3255SM
Stir/Freeze Coil 3D2404R
Stir/Freeze Wire (pack of 2) 3LH243
Quick Instruction Card (English/French) 3250-7
Quick Instruction Card (German/Spanish) 3250-70
Quick Instruction Card (Italian/Swedish) 3250-71
User’s Guide 3255
Service Manual 3255SM
Yoke 3LH230
Power Cord (specify voltage and country)
Barcode Scanner 330016
Printer Maintenance Kit (Serial Suffix A-C only) FL0425
Printer Paper, pkg rolls FLA835
Printer Paper Roll Holder FL0408

11
3250 Controls and Calibration Standards
Part description Part No.
Serial Port Computer Cable with DB9S RS232-CABLE
Supervisor Keys 3D3185
3250 Controls and Calibration Standards
Description Part No.
Clinitrol™ 290 mOsm/kg Reference Solution (ten 5 mL
ampules)
3LA029
Five-Level Osmolality Linearity Set: 100, 500, 900, 1500 and
2000 mOsm (ten 5 mL ampules, two of each value)
3LA028
Protinol™ 3-Level Protein Control Kit (nine 3 mL bottles, three
of each level)
3MA028
Renol™ Urine Osmolality Controls (eight 3 mL bottles, two
levels)
3LA085
0 mOsm/kg Calibration Standard (ten 2 mL ampules) 3MA000
100 mOsm/kg Calibration Standard (110 mL bottle) 3LA010
100 mOsm/kg Calibration Standard (ten 5 mL ampules) 3LA011
500 mOsm/kg Calibration Standard (110 mL bottle) 3LA050
500 mOsm/kg Calibration Standard (ten 5 mL ampules) 3LA051
900 mOsm/kg Calibration Standard (110 mL bottle) 3LA090
900 mOsm/kg Calibration Standard (ten 5 mL ampules) 3LA091
1500 mOsm/kg Calibration Standard (110 mL bottle) 3LA150
1500 mOsm/kg Calibration Standard (ten 5 mL ampules) 3LA151
2000 mOsm/kg Calibration Standard (ten 5 mL ampules) 3LA201
3000 mOsm/kg Calibration Standard (ten 5 mL ampules) 3LA301
Advanced Instruments cannot guarantee the stated instrument performance specifications
and accuracy of test results unless Advanced Instruments brand consumables are used with
the instrument. Use of consumables from manufacturers other than Advanced Instruments is
not recommended and may adversely affect system calibration, performance, operation, and
accuracy of test results. For information on obtaining these standards and controls, contact
Advanced Instruments or an authorized representative.

12
4250 Supplies, Parts, and Accessories Advanced™ Osmometer 3250/Cryoscope 4250 Service Manual
4250 Supplies, Parts, and Accessories
Part description Part no
-422 m°H Calibration Standard (-408 m°C) 3LA023
-621 m°H Calibration Standard (-600 m°C) 3LA033
-530 m°H Lactrol® 530 Reference Solution (-512 m°C) 3LA030
Air Filters, Disposable 3D2340
Barcode Scanner 330016
Heat Transfer Fluid 3DA811
Power Cord (specify voltage and country)
Printer Maintenance Kit (Serial Suffix A-C only) FL0425
Printer Paper (5 rolls) FLA835
Printer Paper Roll Holder FL0408
Sample Tubes marked at 2-mL and 2.5-mL 3LA823
Sample Tube Rack 3LA846
Serial Port Computer Cable with DB9S RS232-CABLE
Service Manual 3255SM
Supervisor Keys 3D3185
User’s Guide 4255
4250 Reference Solutions and Calibration Standards
Part description Part no
-422 m°H Calibration Standard (-408 m°C) 3LA023
-621 m°H Calibration Standard (-600 m°C) 3LA033
-530 m°H Lactrol® 530 Reference Solution (-512 m°C) 3LA030

13
1Overview
Product Description
Advanced™ osmometers and cryoscopes determine the concentration of solutions through
freezing-point depression measurement. Osmometers are used primarily to measure body
fluids such as serum and urine, and cryoscopes are used to determine the freezing points of
various liquids and to detect added water in milk. Application information is available upon
request.
Except for different cooling assemblies, stir/freeze wires, sample sizes and software,
the 3250 and the 4250 are identical to one another. For clarity when replacing parts or
troubleshooting, the instructions indicate any significant differences between the two
instruments.
The Service Manual
This Service Manual contains:
• Instructions for performing repairs
• Guides for troubleshooting operational and mechanical problems
• Circuit system illustrations
• Information about replacement parts and service repairs
This manual is designed to assist service technicians, and does not imply a license to perform
repairs without proper qualifications.
Service Assistance
To contact Advanced Instruments Product Service:
• Call [phone] (toll-free within the USA and Canada; after normal business hours,
dial extension 2191)
• Call +US [phone] (elsewhere)
• Fax [phone]
• Email [e-mail]
When calling Advanced Instruments, have the model and serial number from the label on the
back of the instrument, and a description of the problem. Use a telephone as close to the
instrument as possible in order to facilitate making recommended diagnostic checks.
A service technician may assist in making minor repairs over the phone, providing you with
recommended parts (or part numbers), or may issue an authorization (RMA) to ship the
instrument for factory repair.

14
3250/4250 Components Advanced™ Osmometer 3250/Cryoscope 4250 Service Manual
The RMA procedure is as follows:
1. Contact Advanced Instruments to obtain an RMA.
2. Pack and ship the instrument in its original carton. Do not send instrument supply items.
3. Prepay shipment to the factory. Advanced Instruments cannot accept collect shipments.
Insure the shipment or accept the damage risk.
3250/4250 Components
The following diagram indicates the main components in 3250 osmometers and 4250
cryoscopes with serial suffix A-C.
A
B
Q
T
S
D
C
F
G
R
E
P
JKLM
I
H
U
O
N
A. Head
B. Motor
C. Driver Transistors (Stir,
Thermoelectric)
D. Motor Capacitor
E. Head Up/Head Down
Relays
F. Power Entry Module
G. RS-232C Port
H. Supervisor/Operator
Keyswitch
I. Barcode Port
J. Power Supply
K. Sample Probe Plugin
L. Block Probe Plugin
M. Main Board Set,
Application PCB
N. Main Board Set, Processor
PCB
O. Printer
P. Keypad Transition Board
Q. Keypad
R. Display
S. Deck
T. Heat Transfer Return Tube
U. Heat Transfer Inlet Tube

15
3250/4250 Components Overview
The following diagram indicates the main components in 3250 osmometers and 4250
cryoscopes with serial suffix D and later.
A
B
O
R
Q
D
C
P
E
N
HIJK
G
F
S
M
L
(underneath printer)
A. Head
B. Motor
C. Driver PCB
D. Power Entry Module
E. RS-232C Port
F. Supervisor/Operator
Keyswitch
G. Barcode Port
H. Power Supply
(underneath printer)
I. Sample Probe Plugin
J. Block Probe Plugin
K. Main Board Set,
Processor PCB
L. Printer
M. Main Board Set,
Application PCB
N. Keypad Transition Board
O. Keypad
P. Display
Q. Heat Transfer Return
Tube
R. Heat Transfer Inlet Tube
S. Deck

16
2Calibration
The 3250 has two ranges, each with its own calibration.
• To calibrate the low range, three freezing-point tests are required at the 0 mOsm/Kg H₂O
(if enabled) and 100 mOsm/kg levels, and six tests are required at the 1500 mOsm/kg
level.
• To calibrate the high range, six freezing-point tests are required at both the 1500 mOsm/
kg level and the 3000 mOsm/kg level.
The 4250 allows timed or plateau-seeking calibration in either the Hortvet (m°H) or
the Celsius (m°C) scale. Six freezing-point tests are required at each of the 4250’s two
calibration levels:
• -408 m°C (-422 m°H)
• -600 m°C (-621 m°H)
Note If you see the message Recalibration Needed, follow the instrument prompts to
complete the initial calibration. Your calibration may vary slightly from that mentioned
here.
Refer to the Model 3250 or Model 4250 user's guide for additional information on calibration.
Calibrate the instrument according to the instructions below:
1. Turn the instrument on.
2. If there is a Supervisor/Operator keyswitch, turn it to the Supervisor position. It must
remain there throughout calibration.
3. To enable the optional Zero Calibration:
a. Press SETUP
b. Press < or > to cycle to the Zero calibration option
c. Press START.
d. Press ENTER at the On option.
4. Press CALIB to begin the calibration sequence.
5. The display will prompt you at each calibration level. Place a sample of the first
calibration standard into the freezing chamber and press START.
6. Continue loading and testing samples at the first calibration level until the display
prompts you for samples at the second calibration level.
7. Place the sample of the second calibration standard into the freezing chamber and press
START.
8. When the instrument has completed calibration, the display will read Calibration
Complete.

17
33250/4250 Circuit Description
The instrument is comprised of the following functional blocks:
Processor
Board
Serial Port Applications
Board
Cooling
System
Power
Supply
Head Motor
Controls PrinterKeypadDisplay
Barcode
Port
Power Supply (Serial Suffix A - C)
The power entry assembly interfaces the AC voltage presented to the instrument with the
transformer. The transformer provides 120 VAC to the power supply board and the head
motor. The power supply provides the power to run the main printed circuit board (±12 VDC,
±5 VDC), the thermoelectrics (5 VDC), the fan (12 VDC), the stir/freeze coil (12 VDC), and the
internal printer (5 VDC).
Note The internal printer may be powered by +5 VDC (red/orange wire) or +12 VDC (violet
wire). Consult system schematics for proper service.

18
Power Supply (Serial Suffix D and Higher) Advanced™ Osmometer 3250/Cryoscope 4250 Service Manual
Power Supply (Serial Suffix D and Higher)
The power entry assembly interfaces the AC voltage presented to the instrument with the
AC/DC switching power supply. The power supply provides the power to run the main
printed circuit board set (±12 VDC, +5 VDC), the thermoelectrics (5 VDC), the fan (12 VDC),
the stir/freeze coil (12 VDC), the internal printer (12 VDC), and the motor and control circuits
(+24 V).
Front End
The sample thermistor measures the temperature of the sample. The thermoelectrics (whose
duty cycle is controlled through the block probe/thermistor) supercool the sample. The stir/
freeze wire constantly stirs the sample to guarantee uniform cooling. When the supercooled
sample reaches a set temperature (3000 mOsm for the low range and 4800 mOsm for the
high range, by default, in the 3250, and 3000 m °C in the 4250), the stir/freeze wire "buzzes"
causing the sample to freeze. During a test, the fan duty cycle tracks the thermoelectrics
duty cycle -10%. If duty cycle drops below 20%, the fan is off. In between tests, the fan runs
as required to maintain the software controlled target temperatures.
325605 Control Board Set Description
General: The control board set is made up of two printed circuit boards in a motherboard/
daughterboard configuration.
325620/425620/325621/425621 Processor Board
Processor: The processor used is an Intel 80C186 16-bit embedded processor. The 80C186
contains three programmable 16-bit timers, two serial ports, programmable interrupts, 1
mega-byte of memory address space, and 64 kilobytes of input/output (I/O) address space.
The processor uses an external 32 MHz crystal to generate the internal 16 MHz system clock.
The processor controls access to all memory and all I/O.
Memory Map: The 1 mega-byte of memory address space contains read-only memory (Flash
EPROM), read/write memory (static RAM), and the real time clock. About half of the address
space is unused, allowing for future expansion. The read-only memory is divided into four
sections: reset vector, boot code, parameter blocks (unused), and application code. The reset
vector tells the processor where to first start executing code; in this case, the boot code is
executed first after reset. The boot code determines if new software will be downloaded by
checking if the dip switch is in the “PROGRAM” position.
If it is, the boot code waits for new software to be downloaded through the serial port. If not,
the application code starts.
The real time clock maintains the current date and time, and contains nonvolatile memory
where the instrument’s operation parameters are stored. A internal lithium battery preserves
the contents of the nonvolatile memory when the instrument is turned off. Finally, the read-
write memory is used for stacks, variables, etc., except for the small section allocated for the
interrupt vectors. The interrupt vectors tell the processor what code to run when an interrupt
occurs, and functions similarly to the reset vector.
Please note that all memory addresses and sizes are always defined in terms of bytes, even
though the processor handles words (1 word = 2 bytes, 1 byte = 8 bits; therefore, 16 bits = 1
word).

19
PCB605 Application Board 3250/4250 Circuit Description
Input/Output Map: The 64 kilo-bytes of I/O address space control access to all peripherals
such as the serial ports, application board, etc. The processor uses 256 bytes, called the
Peripheral Control Block, to control the integrated serial ports, timers, interrupts, chip selects,
and I/O pins. The Peripheral Control Block is fully described in the 80C186EB/80C188EB
Microprocessor User’s Manual. The application board’s registers and the CPU board’s
registers control access to various functions and are described later.
Memory: Two types of memory are avail able: read-only and read/write. The chips used
here have 8-bit wide data buses. Used in pairs, the memory becomes compatible with the
processor’s 16-bit wide data bus. The read-only memory is implemented using two 128 kilo-
bytes x 8 bits Flash EPROMs. Flash memory is only programmable when a programming
voltage (in this case, 12 volts DC) is applied to the memory; otherwise, it behaves like read-
only memory. The boot code controls the programming voltage, since this is the only place
where new software can be downloaded. The read/write memory is implemented using two
128 kilo-bytes x 8 bits static RAMs.
Watchdog Timer: The watchdog timer provides a mechanism to reset the processor when
the software is not behaving normally. The software “pets” the watchdog every
100-200 milliseconds. As long as the watchdog is “petted”, nothing happens. However, if the
software stops “petting” the watchdog, the watchdog “bites” the processor by activating
the processor’s RESET pin, causing the processor to reset. The watchdog will also reset the
processor if the power supply falls below 4.75 VDC. These two features allow the instrument
to recover from abnormal software and hardware conditions.
Real Time Clock (RTC): The real time clock maintains the current date and time. The
RTC uses an internal clock circuit with an internal, 10-year life, lithium battery to perform
timekeeping. The battery also preserves the contents of internal memory.
Dip Switch: The three-position or four-position dip switch allows the user to download new
software via one switch. The other two switches are available for selecting different operating
modes. These operating modes and the process for downloading software are described later
in this manual.
Voltages: Three voltages are present on the CPU board: +5 VDC, +12VDC, and VPP.
• +5 VDC powers all the logic.
• +12 VDC is switched on and off to create the flash memory’s programming voltage, VPP.
Glue Logic: The glue logic performs the functions of creating the RAM memory chip selects,
the Flash memory write signals, the VPP control signal, the watchdog control signal, and
accessing the dip switch. The CPU board has two software accessible hardware registers to
read the dip switch and to control watchdog and VPP.
Connectors: A 64-pin connector provides address, data and interrupt signals. A 16-pin
connector provides general chip selects and serial receive/transmit signals. The application
PCB uses a subset of the available signals.
PCB605 Application Board
The application PCB contains all circuitry specific to the instrument. The board includes
voltage supplies, indicators, analog-to-digital converters, drive circuitry, parallel ports, serial
ports, and various switches.
Analog-to-Digital Converters: Two analog-to-digital converters are provided; one for the
sample thermistor probe, and one for the block thermistor probe. The thermistors vary in
resistance from approximately 2 kilo-ohms at room temperature, to approximately 10 kilo-
ohms at -12ºC. Typically, a 0.6 ohm change in the thermistor’s resistance equates to a 1

20
PCB605 Application Board Advanced™ Osmometer 3250/Cryoscope 4250 Service Manual
mOsm/1.86mºC change. A separate Wheatstone bridge circuit is used to measure the voltage
across each thermistor probe.
This voltage is first filtered and then sampled by the analog-to-digital converter. The analog-
to-digital converter uses a sigma-delta conversion technique with on-chip filtering and a 6.25
VDC reference voltage.
I/O Ports: Circuitry for the two serial ports (RS-232 and barcode) and the parallel printer is
present on the application board, with cabling to the actual connectors on the back panel
and the internal printer.
Display & Keypad: The display and keypad are interfaced to the processor via programmable
logic devices (PLDs). The keypad is polled in a row/column process which identifies the key
pressed to the microprocessor.
The application logic, in response to processor commands, controls the LEDs located on the
keypad.
Light Emitting Diodes (LED): LEDs are provided to indicate when a high current load is
active, a sensor is tripped, or a voltage supply is active. Green LEDs are used on the power
supply voltages, yellow LEDs are used on driver signals such as the fan and head motor
controls, and red LEDs are used to indicate that the head up and down optical sensors have
been tripped.
Application Logic: The application logic is made up mainly of two programmable logic
devices (PLDs). These provide software accessible hardware registers, enabling the software
to read the keypad, sensors, and analog-to-digital converters. These also allow manipulation
of the display, external components such as the fan, head motor, etc., and interface to the
RS-232 ports. The printer is controlled directly from the microprocessor through an 8-pin
D-latch.
Connectors: Connectors are supplied for the CPU PCB, display, keypad, power, drives, probes,
and back panel I/O ports.
Serial (RS-232) Port Interface: An RS-232 line driver/receiver provides the microprocessor
with a serial port interface that supports both hardware and software handshaking.
The DB-9 RS-232 port conforms to the DTE RS-232C standard and has the following pin
assignments:
Signal Pin Direction
Carrier Detect 1to 3250
Receive Data 2to 3250
Transmit Data 3from 3250
Data Terminal Ready 4from 3250
Signal Ground 5 common
Data Set Ready 6to 3250
Request to Send 7from 3250
Clear to Send 8to 3250
Note that your instrument is only designed to support unidirectional communication with an
external device. At this time, there is no protocol for bidirectional communication.
For a sample RS-232 Port Setup, please see the Supplemental RS-232 Information in the
Appendix at the end of this user’s guide.