MIRAK 725 series User manual

LT727X7 • 9/9/99 Serial Number: _______________________________
BARNSTEAD|THERMOLYNE CORPORATION
MIRAK™ Hot Plates,
Stirrers and
Stirring Hot Plates
OPERATION MANUAL
AND PARTS LIST
SERIES 725, 726, 727, 728, 729, 730
Model # Voltage Description
HP72620 240 7x7
HP72620-26 220-240 7x7
HP72624 100 7x7
HP72625 120 7x7
S72520 240 7x7
S72520-26 220-240 7x7
S72524 100 7x7
S72525 120 7x7
SP72720 240 7x7
SP72720-26 220-240 7x7
SP72724 100 7x7
SP72725 120 7x7
HP72930 240 12x12
HP72930-26 220-240 12x12
HP72934 100 12x12
HP72935 120 12x12
HP72935-60 120 12x12
HP72938 208 12x12
S72830 240 12x12
S72830-26 220-240 12x12
S72834 100 12x12
S72835 120 12x12
SP73030 240 12x12
SP73030-26 220-240 12x12
SP73034 100 12x12
SP73035 120 12x12
SP73035-60 120 12x12
SP73038 208 12x12

2
IMPORTANT INFORMATION
This manual contains important operating and safety information. The user must carefully
read and understand the contents of this manual prior to the use of this equipment.
Table of Contents
Safety Information.........................................................................................................................3
Alert Boxes..................................................................................................................................3
Warnings......................................................................................................................................3
Introduction..................................................................................................................................5
Unpacking....................................................................................................................................5
Installation....................................................................................................................................7
Principles of Operation..................................................................................................................7
Operation.....................................................................................................................................8
Removing the Clear Plastic Cover ..............................................................................................8
The Power Switch.....................................................................................................................8
Setting the Stirring Speed.........................................................................................................8
Stirring Speed Guide................................................................................................................9
Setting the Temperature...........................................................................................................9
Controlling Top Plate Temperature..........................................................................................10
Controlling Solution Temperature............................................................................................10
Calibrating the Probe Temperature Input..................................................................................11
Using the Probe with the Temperature Display for Stirring-only Applications...............................11
To Achieve Fast Heat-up of Large Volumes..............................................................................12
Heating Small Volumes ...........................................................................................................12
Heating Metal Vessels and Sand Baths....................................................................................12
Heat-up Time Guide................................................................................................................12
Operating Specifications.............................................................................................................14
Heating Specifications............................................................................................................14
Stirring Speed Specifications..................................................................................................14
General Operating Specifications.................................................................................................15
Dimensions- 7" x 7" Models\l 2.....................................................................................................15
Dimensions- 12" x 12" Models\l 2.................................................................................................15
Electrical Ratings- 7" x 7" Models\l 2.............................................................................................15
Electrical Ratings- 12" x 12" Models\l 2.........................................................................................16
Temperature Range for Hot Plates and Stirring Hot Plates .........................................................16
Stirring Speed Range for Stirrers and Stirring Hot Plates............................................................16
Environmental Parameters for all units......................................................................................16
Maintenance and Servicing.........................................................................................................17
Replacing the Power Board.....................................................................................................17
Replacing the Logic Board......................................................................................................18
Replacing the Display Board....................................................................................................18
Replacing the Motor................................................................................................................18
Replacing the Top Plate Assembly...........................................................................................19
Set-up Procedure...................................................................................................................20
Troubleshooting Guide...........................................................................................................21
Replacement Parts List...............................................................................................................25
Ordering Procedures..................................................................................................................26
Warranty.....................................................................................................................................27

3 Barnstead|Thermolyne • 800-553-0039
Safety Information
Your Thermolyne MIRAK™ stirrer, hot plate, or stirring hot plate has been designed with function,
reliability, and safety in mind. It is your responsibility to install it in conformance with local electrical codes.
Alert Signals
WARNING
Warnings alert you to a possibility of personal injury.
CAUTION
Cautions alert you to a possibility of damage to the equipment.
NOTE
Notes alert you to pertinent facts and conditions.
Warnings
WARNING
To avoid electrical shock, always:
1. Use a properly grounded electrical outlet of correct voltage and current handling capacity.
2. Disconnect from power supply before servicing.
To avoid personal injury:
1. Do not use in the presence of flammable or combustible materials; fire or explosion may result.
This device contains components which may ignite such materials.
2. Keep top surface clean. Use a non-abrasive cleaner. Alkali spills, hydrofluoric acid spills or
phosphoric acid spills may damage top and lead to thermal failure. Unplug unit and remove spills
promptly. Do not immerse unit for cleaning.
3. Replace the top immediately if damaged by etching, scratching or chipping. A damaged top can
break in use.
4. Do not remove or modify grounded power plug. Use only properly grounded outlets to avoid
shock hazard. Not rated for use in hazardous atmospheres.
5. Use caution when heating volatile materials; top surface and element can reach the “Flash Point
Temperature” of many chemicals. These hot plates and stirring hot plates are not explosion proof.
Fire or explosion may result. Unit contains components which may ignite such materials.
6. Use appropriate hand and eye protection when handling hazardous chemicals.
7. "Caution: Hot Surface. Avoid Contact." The hot plate will remain hot without any visual indication
for some time after power has been removed.
8. Do not use in highly corrosive atmospheres; corrosive fumes and spill may damage top and
internal components, creating shock hazard.
9. Refer servicing to qualified personnel.
CAUTION
Space unit 12 inches away from combustible materials under any conditions.
Gross weight of items placed on top of Hot Plates should not exceed 25 lbs. on the 7" X 7"
and 30 lbs. on the 12" X 12" models.

4
Please note the following WARNINGS:
WARNING
This warning is presented for compliance with California Proposition 65 and other
regulatory agencies and only applies to the insulation in this product. This product
contains refractory ceramic, refractory ceramic fiber or fiberglass insulation,
which can produce respirable dust or fibers during disassembly. Dust or fibers
can cause irritation and can aggravate pre-existing respiratory diseases.
Refractory ceramic and refractory ceramic fibers (after reaching 1000°C) contain
crystalline silica, which can cause lung damage (silicosis). The International
Agency for Research on Cancer (IARC) has classified refractory ceramic fiber
and fiberglass as possible carcinogenic (Group 2B), and crystalline silica as
carcinogenic to humans (Group 1).
The insulating materials can be located in the door, the hearth collar, in the chamber of
the product or under the top plate top. Tests performed by the manufacturer indicate
that there is no risk of exposure to dust or respirable fibers resulting from operation of
this product under normal conditions. However, there may be a risk of exposure to
respirable dust or fibers when repairing or maintaining the insulating materials, or
when otherwise disturbing them in a manner which causes release of dust or fibers
therefrom. By using proper handling procedures and protective equipment you can
work safely with these insulating materials and minimize any exposure. Refer to the
appropriate Material Safety Data Sheets (MSDS) for information regarding proper
handling and recommended protective equipment. For additional MSDS copies, or
additional information concerning the handling of refractory ceramic products, please
contact the Customer Service Department at Barnstead|Thermolyne Corporation at
1-800-553-0039.
WARNING
REFER SERVICING TO QUALIFIED PERSONNEL.

5 Barnstead|Thermolyne • 800-553-0039
Introduction
Please read all the information in this manual before operating the unit.
Your Thermolyne MIRAK™ hot plate, stirrer or stirring hot plate is a general purpose heating and/or stirring
plate designed for laboratory procedures requiring precise control of temperature and/or stirring speed.
Each MIRAK model includes a digital display for monitoring actual temperature or stirring speed, and the
stirring hot plate models have dual displays so temperature and stirring speed can be monitored
simultaneously. The hot plate is capable of producing accurately controlled top plate temperatures from
40°C through 540°C on all 7" x 7" models and the 208 volt and 240 volt models of the 12" x 12" hot plates.
(12" x 12" 100 volt and 120 volt models have a temperature range of 40°C to 370°C.) The temperature
may be controlled at the plate surface by an internal Type K thermocouple sensor, or the solution
temperature may be controlled by utilizing an accessory ungrounded Type K thermocouple probe. A 6" or
10" general purpose stainless steel immersion probe, or a chemical-resistant 7" solid Teflon®immersion
probe may be ordered separately. The stirrer will accurately maintain stirring speeds from 60 rpm up to
1200 rpm. On stirring hot plate models, the accessory probe may also be utilized to display the actual
temperature of heat-sensitive solutions during stirring-only functions. The 7" x 7" or 12" x 12" top plate on
the MIRAK units is solid ceramic, and is suitable for use with glass or metal vessels.
Your MIRAK hot plate, stirrer or stirring hot plate may be used for general purpose heating applications
and/or general laboratory mixing of solutions, including sample preparation, heating reagents, melting
paraffin, warming resinous chemicals, content analysis, solvent evaporations, digestions, media
preparation and sterilization, titrations, sand baths, and microscale chemistry applications.
Unpacking
Remove your MIRAK hot plate, stirrer or stirring hot plate from the carton. Inspect to ensure that the unit
has not been damaged during shipment. If the unit appears to have sustained shipping damage contact
the distributor from whom you purchased this product or Barnstead/Thermolyne Customer Service at 800-
553-0039. Remove the packaging from underneath the top plate by gently pulling the packaging material
toward you.
NOTE
A special 20-amp cord set is included on the CSA-approved models of
the 12" x 12" 120 volt MIRAK hot plate and stirring hot plate
(HP72935, SP73035). This 20-amp cordset can only be plugged into
a non-standard 20-amp, 120 volt receptacle. If you do not have the
appropriate receptacle, contact a qualified electrician for installation of
a 20-amp 120 volt outlet.
A 12" x 12" 120 volt MIRAK hot plate and stirring hot plate (HP72935-
60, SP73035-60) is available with a standard 15-amp, 120 volt cordset.
These models are not CSA-approved.
20-amp, 120 volt
15-amp, 120 volt

6

7 Barnstead|Thermolyne • 800-553-0039
Installation
WARNING
Use a properly grounded electrical outlet of correct voltage and current handling capacity.
Do not remove or modify grounded power plug. Use only properly grounded outlets to avoid
shock hazard. Not rated for use in hazardous atmospheres.
Do not use in the presence of flammable or combustible materials; fire or explosion may
result. This device contains components which may ignite such materials.
Do not use in highly corrosive atmospheres; corrosive fumes and spill may damage top and
internal components, creating shock hazard.
Set the unit on a flat stable surface at least 12" away from combustible materials, and plug the cordset into
a properly grounded electrical outlet of correct voltage and current handling capacity. Use your right hand
to locate the ON/OFF power switch which is on the side, near the front right corner as you face the unit.
Press the black ON/OFF power rocker switch into the ON position. The red LED display(s), and the green
power light to the left of the display(s) should illuminate. The unit is ready for operation.
NOTE
Some misalignment of the motor bearings in this product may have occurred during shipping.
Prior to using this product, run the stirrer at maximum speed for ten minutes to realign the
bearings.
Principles of Operation
Each MIRAK unit utilizes the latest in microprocessor technology to deliver the most reliable, accurately
controlled, ceramic top hot plate, stirrer and stirring hot plate on the market.
Your MIRAK hot plate or stirring hot plate has an electronic closed-loop feedback control which will
accurately maintain temperature setpoints from 40°C through 370°C or 540°C, depending on the model.
The top plate surface temperatures are calibrated and verified at the factory using the latest in infrared
temperature measurement. The measurements are made with an infrared camera mounted approximately
26" above the top surface of the hot plate or stirring hot plate. If the temperature measurement of the
ceramic top is made with measurement devices other than infrared, the error of the measuring technique
may be greater than the error of the unit.
The MIRAK units use a Type K thermocouple for measuring both the top plate temperature, and the
solution temperature when using the probe. Both top plate surface and probe temperature are measured
with independent analog circuits. This provides a significant increase in reliability due to the redundancy of
the circuit. Because of the dual sensors it is possible to heat certain types of metal vessels and sandbaths
on the MIRAK without damaging the ceramic top. However, we recommend that you do not control the
temperature with the probe when heating a metal vessel or a sandbath.
The electronic stirring speed control will maintain the speed setpoint when the unit is loaded at ±2 RPM as
displayed by the LED display on the unit. The motor in the MIRAK stirrers and stirring hot plates produces
maximum stirring torque under normal laboratory load conditions, and is combined with a powerful magnet
to provide exceptional magnetic coupling with a stirbar.

8
Operation
WARNING
Use caution when heating volatile materials; top surface and element can reach the “Flash
Point Temperature” of many chemicals. These hot plates and stirring hot plates are not
explosion proof. Fire or explosion may result. Unit contains components which may ignite
such materials.
Use appropriate hand and eye protection when handling hazardous chemicals.
"Caution: Hot Surface. Avoid Contact." The hot plate will remain hot without any visual
indication for some time after power has been removed.
CAUTION
To avoid damage to the top plate or heating element, always keep a vessel filled with liquid on
the top plate of a hot plate or stirring hot plate when the unit is heating or cooling.
Removing the Clear Plastic Cover
Your MIRAK unit has a protective plastic cover over the front control panel. This plastic cover is designed
to protect the control knobs and the display panel from spills, and should remain in place when the unit is
being used. To use the knob(s) while the plastic cover is in place, spin the knob(s) from the bottom where
the knob projects below the plastic cover. This plastic cover can be easily removed for cleaning by
grasping the cover at each bottom corner and gently pulling the sides of the plastic cover away from the
case while lifting the cover toward you. To replace the cover simply slide it back onto the case.
The Power Switch
Your MIRAK unit has a separate ON/OFF power switch which is a black rocker switch located on the lower
front corner of the right side as you're facing the unit. This separate power switch allows you to turn your
MIRAK hot plate, stirrer or stirring hot plate on or off without disturbing your temperature and/or speed
setting. Your last setpoint will be held in memory even if the unit is unplugged and will reappear on the
display as soon as the unit is powered up again. Whenever the power is on, a green power light illuminates
on the front control panel.
Setting the Stirring Speed
Your MIRAK stirrer or stirring hot plate has an electronic feedback speed control which will maintain a
precise speed setpoint from 60 rpm through 1200 rpm at ±2 rpm. (Maximum speed is dependent on
viscosity of the solution.) The MIRAK stirrers and stirring hot plates are equipped with a strong magnet and
high torque motor which will draw a vortex in up to 1800 ml of water stirred in a 2 liter flask with a new 2" stir
bar.
To set the speed, spin the SPEED CONTROL knob until your desired setting is indicated on the digital
display. As you move the knob, the SET light next to the RPM display will illuminate. Turn the knob
clockwise to increase the speed or counterclockwise to decrease the speed. The unit will not start to stir
until you press the speed control knob. Once the unit begins stirring the display will register ACTUAL
speed and the SET light will no longer be illuminated. To check your setpoint, move the knob
counterclockwise one position. You will feel a click, the SET light will illuminate, and your setpoint will be
displayed again for five seconds. After five seconds the display will automatically return to indicating actual
speed and the SET light will go out. To stop the stirring action without changing your setpoint press the
knob once. To resume stirring at the set speed, press the knob again.

9 Barnstead|Thermolyne • 800-553-0039
If you want to ensure that the unit will not start to stir if the knob is inadvertently pressed, turn the speed
control knob until the display indicates the word OFF.
Stirring Speed Guide
Unit Flask Size Stirbar Size Amount of Solution Viscosity Maximum Speed*
7" x 7" MIRAK 1 liter 2" 800 ml water 1200 rpm
7" x 7" MIRAK 2 liter 2" 1800 ml water 1200 rpm
7" x 7" MIRAK 1 liter 2" 1000 ml Cooking oil 700 rpm
7" x 7" MIRAK 500 ml 2" 350 ml 30 weight
motor oil 1100 rpm
*Maximum speed obtained without the stir bar loosing coupling with the magnet.
The 12" X 12" MIRAK stirrers and stirring hot plates will produce stirring speed results similar to those
provided above for the 7" X 7" units. For speed stability and display accuracy please refer to the Operating
Specifications on page 13.
Setting the Temperature
Your MIRAK hot plate or stirring hot plate has an electronic closed-loop feedback control which will
accurately maintain temperature setpoints from 40°C through 370°C or 540°C, depending on the model.
An unloaded hot plate will heat to maximum temperature in just 8 minutes. A HOT light on the front panel
will illuminate whenever the top surface temperature exceeds 50°C. The temperature may be controlled
either at the top plate by the internal Type K thermocouple sensor, or in the solution using an accessory
ungrounded Type K thermocouple probe. (A 6" or 10" stainless steel general purpose immersion probe,
or a chemical-resistant 7" Teflon®immersion probe are available through your distributor, or by contacting
Barnstead/Thermolyne, 800-553-0039). Your MIRAK hot plate, stirrer or stirring hot plate will accept any
ungrounded Type K thermocouple probe, however the accuracy of probes other than the ones we've
tested and specified may exceed the probe accuracy rating we've designated.
Your MIRAK hot plate or stirring hot plate will display the temperature in °C. The display will always indicate
'OFF' or your last setpoint, and the 'SET' light will be illuminated until you press the heat control knob to
initiate operation. Once the heat control knob has been pressed the ACTUAL temperature of the top
plate or the probe will be displayed, and the 'SET' light will no longer be illuminated. If you want to check
your setpoint, you do not have to press the knob again, simply turn the knob counterclockwise one click.
Your setpoint will be displayed for approximately five seconds until the display returns to indicating the
actual temperature.
NOTE
The temperature display will not indicate a temperature less than 40°C. If the actual
temperature is less than 40°C, the word 'LO' will be indicated until the actual temperature
reaches 40°C.
If you want to ensure that the unit will not heat if the knob is inadvertently pressed, turn the temperature
control knob until the display indicates the word 'OFF'.

10
Controlling Top Plate Temperature
Your MIRAK hot plate or stirring hot plate will control the top plate, and the display will indicate top plate
temperature WHENEVER THE PROBE IS NOT PLUGGED IN. When the unit is displaying the top plate
temperature the word TOP on the front panel will be illuminated.
Controlling Solution Temperature
To control your solution temperature simply plug an ungrounded Type K thermocouple probe into the
probe receptacle located on the back of the unit, and place the probe in your solution. The display will
indicate the actual temperature of the solution as measured by the probe, and the word PROBE on the
front panel will be illuminated.
NOTE
The top plate temperature will be higher than your solution temperature.
The solution probe offers more exact temperature control than regulating the top plate by the internal
sensor. If you need to maintain a precise setpoint we recommend using a probe to control the solution
temperature instead of controlling the top plate temperature.
When using a probe with your MIRAK hot plate or stirring hot plate it is recommended that you use a clamp
on a support rod to hold the probe in your solution.
To ensure accurate probe readings, as much of the probe sheath as possible should be immersed in your
solution. If the probe is plugged into your hot plate or stirring hot plate while the heat control is operating
but is not in solution, the temperature display will continue to indicate an ambient temperature. Because
the set point cannot be reached the element will continue to supply heat to the top plate, and the
maximum top plate temperature of 540°C may be reached.
WARNING
If the probe is plugged into your stirring hot plate while the heat control is operating but is not
in solution, the temperature display will continue to indicate an ambient temperature.
Because the setpoint cannot be reached, the element will continue to supply heat to the top
plate, and the maximum top plate temperature of 540°C may be reached. Any type K
thermocouple probe used must be an ungrounded type.
NOTE
The top plate temperature will not exceed the 540°C maximum.
To obtain an accurate reading when you are using the probe and stirring your solution, make sure the
probe is immersed in the liquid and is not located in air in the center of the stirring vortex. Drafts and other
temperature fluctuations will affect temperature accuracy.