Gaymar MEDI-THERM II User manual

MEDI-THERM ® II
HYPER/HYPOTHERMIA MACHINE
REF MTA6012CE
P/N 100164000 05/07
SERVICE MANUAL

MTA6012CE Service Manual
Important
• Refer to the Medi-Therm II® Operator’s Manual for detailed
operating instructions. Read and understand the Operator’s
Manual and all precautions prior to using the Hyper/
Hypothermia machine.
• Review the SAFETY PRECAUTIONS (see page 1) prior to
servicing the Medi-Therm II machine.
• For technical assistance, contact your local dealer.
Receiving Inspection
Upon receipt, unpack the Medi-Therm II machine. Save all
packing material. Perform a visual and mechanical inspection for
concealed damage by removing the wraparound from the chassis
(see figure 18, page 55). If any damage is found, notify the carrier
at once and ask for a written inspection. Photograph any damage
and prepare a written record. Failure to do this within 15 days
may result in loss of claim.
Refer to section 2.0 of this Medi-Therm II Service Manual for
additional details.
IMPORTANT
Before operating the Medi-Therm II machine, remove the
compressor shipping braces. See p. 72, figure B, items 8 and 9.
Temporarily remove the power cord retainer (fig. 19, p. 56, item 6)
and install the power cord. Reattach the power cord retainer.
Before you begin . . .
Gaymar® and Clik-Tite® are registered in the U. S. Patent and Trademark Office.
Gaymar®, Clik-Tite®, and Medi-Therm® are trademarks of Gaymar Industries, Inc.
© 2000. Gaymar Industries, Inc. All rights reserved.
Table of Contents
1.0 Safety Precautions ................................... 1
2.0 Repair Policy ............................................ 2
3.0 Specifications ........................................... 3
4.0 Blankets/Accessories ............................... 6
5.0 Operator Control Panel ............................. 8
6.0 Theory of Operation ................................ 10
7.0 Functional Check, Safety Inspection,
and Preventive Maintenance .................. 16
8.0 Service Modes and Troubleshooting ...... 22
9.0 Repair Procedures .................................. 45
10.0 Service Information ................................. 50
Figures
1 Warm-up Rate .......................................... 4
2 Cooldown Rate ......................................... 4
3 Disposable Probe/Reusable Cable ........... 6
4 Medi-Therm II System .............................. 7
5 Medi-Therm II Control Panel ..................... 9
6 Probe Check Well ................................... 17
7 Functional Check/Inspection Form ......... 21
8 Initiating Service Mode 1 ........................ 22
9 RFU Codes ............................................. 23
10A-N Troubleshooting Charts ..................... 26-44
11 Connecting Terminal Block Wires ........... 47
12 Flow Switch ............................................ 48
13 Temperature vs. Resistance Table .......... 50
14 Circuit Boards/Connectors (Head) .......... 51
15A/B Heating Flow; Cooling Flow .................... 52
16 Refrigeration Flow Diagram .................... 53
17A/B Test Setup; Test Setup (alternate) ........... 54
18 Machine Disassembly ............................. 55
19 Parts Diagram (Base), Parts List ............ 56
20 Parts Diagram (Head), Parts List ............ 58
21 Thermostat Wiring Diagram .................... 59
22 Control/Display Board, Parts List ............ 60
23 Power Supply Board, Parts List .............. 62
24 Alarm/Backup Board, Parts List .............. 64
25 Wiring Diagram [foldout] ......................... 66
26 Power Supply Board Schematic,
1 of 4 [foldout] ......................................... 67
27A Control Display Board Schematic,
2 of 4 [foldout] ......................................... 68
27B Control Diplay Board Schematic,
3 of 4 [foldout] ......................................... 69
28 Alarm/Backup Board Schematic,
4 of 4 [foldout] ......................................... 70
29 Block Diagram [foldout] .......................... 71
30 Shipping Instructions .............................. 73

MTA6012CE Service Manual Machine Precautions
1.0 Safety Precautions
Review the following safety precautions prior to testing the
Medi-Therm II machine:
Risk of electric shock. Refer servicing
to qualified medical equipment service
personnel.
• Repairs should be performed only by qualified medical
equipment service personnel and in accordance with
this Service Manual. Otherwise, damage to the
Medi-Therm II machine and improper therapy may
result.
• Do not tip machine over without first draining the water
out and unplugging the power cord. Electrical shock or
damage to the machine can result.
• Use only Gaymar probes (see Accessories, page 6) or
probes having characteristics equivalent to
YSI 400 series probes in the Patient Probe jack.
Use of other probes could result in erroneous
patient temperature values.
Add distilled water only. Failure to use distilled water
may result in poor machine performance.
• Do not use alcohol, since it is flammable. Alcohol
may also accelerate blanket deterioration.
• Do not operate the machine without water, since
damage to internal components may result.
• Do not overfill. Overfilling may result in overflow
because the water in the blanket drains back into
the machine when the machine is turned off.
• For grounding reliability, plug the Medi-Therm II
machine only into a properly grounded outlet.
• To prevent damage to the power cord, always keep
the power cord retainer in place.
DANGER
W
ARNING
CAUTION
1

MTA6012CE Service ManualRepairs/Warranty
2.0 Repair Policy
For customers who repair Gaymar Medi-Therm II machines at
their location, this manual contains information to allow a qualified
biomedical technician, familiar with practices for servicing
medical devices, to make necessary repairs. Service training for
the Hyper/Hypothermia machine is recommended and can be
arranged through your local dealer.
2.1 Limited Warranty
The Medi-Therm II Hyper/Hypothermia machine is warranted free
of defects in material and workmanship for a period of two (2)
years, under the terms and conditions of the Gaymar warranty
in place at the time of purchase. The compressor portion of the
machine carries a five year prorated warranty. During the warranty
period, contact your local dealer.
Warranty does not cover products abused, misused, or altered
outside the factory. There are no obligations on the part of
Gaymar for consequential damages arising out of or in connection
with the use or performance of the product. Gaymar disclaims
all implied warranties including, but not limited to, the implied
warranties of merchantability and of fitness for a particular
purpose.
2.2 Warranty Repairs
All in-warranty field repairs must be authorized by Gaymar’s
Export Department before proceeding.
2.3 Out-of-Warranty Repairs
The following repair options are available when local machine
servicing is elected:
I . Defective Component
Replacement parts can be ordered from your local dealer.
Specify the Gaymar part number; refer to the Parts Lists in
section 10.0 of this manual.
2. Defective Printed Circuit (PC) Board
Defective PC boards can be exchanged for replacement
boards at a fixed cost directly from your local dealer.
3. Defective Top Module
The defective top module can be returned (without base) for
repair. Contact your local dealer for information.
4. Machine Repairs
If the Medi-Therm II machine becomes defective and the
cause of the problem cannot be determined, the complete
machine can be returned to your local dealer for servicing at
the purchaser’s expense. This normally represents the most
expensive repair option. Contact your local dealer.
2
2.4 Return Authorization
Please contact your local dealer.

MTA6012CE Service Manual
3.0 Specifications
3.1 Physical
Specifications
3.2 Thermal
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* Section 9.1.1 for additional information

MTA6012CE Service ManualSpecifications
3.3 Performance
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3.2 Thermal (continued)
Figure 1—Typical warm-up rate
(with full size blanket)
Figure 2—Typical cooldown rate
(with full size blanket)

MTA6012CE Service Manual
3.4 Electrical
3.6 Classification
3.5 Regulatory
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MTA6012CE Service Manual
6
4.0 Blankets/Accessories
Single Patient Use Blankets,
Polymer with Nonwoven Fabric
REF DHP810CE O.R. Table and General Use
(64 cm x 163 cm)
REF DHP812CE Pediatric General Use
(56 cm x 84 cm)
REF DHP813CE Adult General Use
(76 cm x 163 cm)
Single Patient Use Blankets, All Polymer
REF DHP901 Adult General Use
(64 cm x 175 cm)
REF DHP902 Pediatric General Use
(64 cm x 91 cm)
REF DHP903CE Adult General Use (Narrow)
(51 cm x 150 cm)
Reusable Blankets, Heavy Duty Polymer
REF HP7010 Adult General Use
(64 cm x 175 cm)
REF HP7020 Pediatric General Use
(64 cm x 91 cm)
All blankets require use of the reusable DBK35CE
Connector Hose.
Accessories *
(see item 1, p. 57) Detachable Power Cords
REF DBK35CE Connector Hose (3 meters)
REF PAT101CE Reusable Adult Patient Probe (3 meters)
Rectal/Esophageal (YSI 401AC)
REF PAT102CE Reusable Pediatric Patient Probe (3 meters)
Rectal/Esophageal (YSI 402AC)
REF PAT108CE Reusable Patient Probe (3 meters)
Skin Surface (YSI 409AC)
NOTE: Other style YSI 400 series probes are available through
Yellow Springs Instruments.
REF DP400CE Disposable Adult and Pediatric Patient
Probe (0.9 meter) Rectal/Esophageal
[requires ADP10CE Adaptor Cable]
REF ADP10CE Reusable Probe Adaptor Cable
(3 meters) for DP400CE Probe
* These Gaymar probes, adapters, and hoses should be
used only with Gaymar Hyper/Hypothermia Machines.
Blankets/Accessories
Figure 3—Disposable Probe/Reusable Adaptor Cable

MTA6012CE Service Manual
Water Fill Opening
Lift cover. Fill unit with
distilled water until green
band on float is fully visible.
Dual Blanket Connections with
Quick-disconnects and
Probe Check Well
Use PROBE CHECK
well to verify the
integrity of the
patient probe.
Figure 4—Medi-Therm II Hyper/Hypothermia System
ON/OFF Switch
(Circuit Breaker)
Controls power to
Medi-Therm II.
Patient Probe Jack
Accepts patient probe plug connecting patient
probe to machine. Use only Gaymar probes
or equivalent YSI 400 series probes.
Medi-Therm II System
7

MTA6012CE Service ManualOperator Control Panel
MACHINE STATUS
HEAT indicates the machine is heating.
IN-TEMP indicates that the blanket or patient
temperature is at the desired temperature setting.
COOL indicates the machine is cooling.
TEST LIGHTS flashes all indicator lights and
digital displays, while sounding an audible alarm.
ALARM SILENCE temporarily silences the
CHECK FLOW, CHECK PATIENT PROBE,
FLASHING DISPLAY, and ADD WATER alarms
for 10 minutes.
ALERTS
CHECK FLOW indicates the flow of water to the
blanket has been restricted.
CHECK PATIENT indicates the patient probe
is sensing a temperature below 29°C or above
40°C.
ADD WATER indicates the water reservoir is
filled to less than the recommended level.
REMOVE FROM USE NOW indicates
the Medi-Therm II machine has shut down.
Remove the machine from use.
FLASHING DISPLAY indicates that the blanket
or patient temperature is not being maintained
within 0.5°C of the set point temperature. It is
accompanied by an audible alarm.
POWER LOSS INDICATOR lights when
power is removed and ON/OFF circuit breaker
is ON. [located on front of machine]
5.0 Operator Control Panel
See figure 5, page 9.
8

MTA6012CE Service Manual Operator Control Panel
Figure 5—Medi-Therm II Control Panel
SELECT MODE
BLANKET CONTROL—
Adjust SET POINT to control
blanket temperature.
(4°C to 41°C)
PATIENT CONTROL—
Connect patient probe, then adjust
SET POINT to control patient
temperature.
(30°C to 39°C)
MONITOR ONLY—
Connect patient probe, then use to
monitor patient temperature. No
therapy is provided.
TEMPERATURE
BLANKET TEMPERATURE—
This display lights when either PATIENT
CONTROL or BLANKET CONTROL is selected.
PATIENT TEMPERATURE—
As measured by the patient probe.
This display lights whenever a patient probe is
plugged in.
SET POINT CHANGE—
Press the “” or “” button to select machine
set point. When selecting a temperature outside
the normothermic range (36°C to 38°C), an
audible alarm will chime. Press and hold the
“” or “” button until the chime stops to
access the extended temperature range.
PATIENT PROBE JACK—
Insert only a Gaymar probe or an equivalent
YSI 400 series probe. [located on front of
machine]
9

MTA6012CE Service ManualTheory of Operation
6.0 Theory of Operation, System
The Gaymar Medi-Therm II machine provides a means of regu-
lating patient temperature by supplying temperature-controlled
water through a connector hose to a Gaymar Hyper/Hypothermia
blanket. The blanket provides an interface for heating or cooling
the patient. A patient probe senses patient temperature, which is
displayed on the control panel. (See fig. 4, p. 7 and fig. 5, p. 9.)
The Medi-Therm II machine controls output water temperature
by mixing hot and cold water using hot and cold solenoid valves
under microcontroller control. A circulating pump, heater and
refrigeration unit are also utilized.
Two backup systems limit output water temperature independent
of the main microcontroller.
The feedback for control purposes depends upon the machine’s
operating mode. The machine may be operated in one of three
operating modes:
• In BLANKET CONTROL mode, the operator sets the
desired blanket temperature. A temperature sensor
within the machine monitors the water temperature
and the machine heats or cools the water as required
to bring the blanket to the SET POINT temperature.
The patient temperature may be monitored by use of a
patient probe connected to the patient probe jack on the
front of the unit.
• In PATIENT CONTROL mode, the Medi-Therm
II machine automatically regulates the patient’s
temperature to the selected SET POINT. The machine
constantly compares actual patient temperature with the
SET POINT value, and automatically adjusts the blanket
temperature so that the desired patient temperature is
achieved.
• In MONITOR ONLY mode, the operator can monitor
patient temperature through the patient probe, without
providing therapy.
Hyperthermia/hypothermia blankets may be placed either under
or over the patient, depending upon the type of procedure. Some
applications may require a second blanket in order to achieve
additional or more rapid heating or cooling. For these situations, a
second blanket may be connected to the Medi-Therm II machine.
The rate of patient heating or cooling may also be increased
by positioning half- and full-sized blankets so that greater body
surface is in contact with the blankets.
In the event of a power loss, a battery backup circuit will light the
POWER LOSS light and sound the audible alarm. Upon restoring
power, the mode of operation and the set points will have to be
reselected.
6.1 Theory, Medi-Therm II Machine
Whenever the machine is on, 91/2 liters of water are maintained
cold in the cold water reservoir. A cold water reservoir probe
provides temperature feedback to the main microcontroller which
cycles the refrigeration unit on at 5.8°C and off at 3.3°C.
When the blanket water requires cooling, water is pumped from
the cold water reservoir. When the blanket water requires heating,
a cartridge heater is used to quickly heat the water.
WATER TEMPERATURE CONTROL
Hot and cold solenoid valves regulate the flow path by directing
water returning from the blanket to either the hot or cold water
reservoir. Regulating the flow path controls the temperature of
water pumped to the blanket. The main microcontroller controls
solenoid valve operation. Only one valve operates at a time:
• When the HEAT status light is lit, the hot solenoid valve
is open. Water returning from the blanket circulates
through the hot water reservoir and is heated before
being pumped back to the blanket. The heater, pump,
and hot solenoid valve are energized. See figure 15A,
page 52.
• When the COOL status light is lit, the cold solenoid
valve is open. Water returns from the blanket to the
cold water reservoir and is replenished by chilled water
from the cold water reservoir before being pumped back
to the blanket. The pump and cold solenoid valve are
energized. See figure 15B, page 52. The refrigeration
unit maintains the cold water reservoir temperature and
operates independently of the solenoid status.
• When the IN-TEMP status light is lit, either the blanket
water temperature is within 0.5°C of the setpoint (in
BLANKET CONTROL mode) or the patient temperature
is within 0.5°C of the setpoint (in PATIENT CONTROL
mode). Water temperature is controlled by alternating
between heating and cooling (see figs. 15A and 15B, p.
52).
REFRIGERATION UNIT
The refrigeration circuit (see fig. 16, p. 53) consists of two
heat exchangers operating at two pressures and two devices
used to change these pressures. The first of these devices is
the compressor which changes the gas pressure from low to
high. The other device is the capillary tube which reduces the
refrigerant pressure from high to low.
Beginning the cycle at the capillary tube, high pressure liquid
refrigerant flows in the capillary tube and is discharged into the
evaporator coil. The evaporator coil, which is a heat exchanger,
receives the refrigerant as a mixture of liquid and vapor at a
pressure low enough so that it boils and absorbs heat from the
water surrounding it.
10

MTA6012CE Service Manual
The heated refrigerant vapor then leaves the evaporator coils,
enters the suction side of the compressor and is compressed,
causing its pressure and temperature to increase. The vapor,
much warmer than the ambient air, travels to the condenser.
The condenser is the other heat exchanger. The condenser
fan draws the colder ambient air over the condenser coils and
removes the heat being carried by the refrigerant and causes
it to condense back into liquid refrigerant. This completes the
cycle and the high pressure liquid refrigerant is returned to the
capillary tube to be used over again. The temperature of the water
surrounding the evaporator coil (in the cold water reservoir) is
controlled by the main microcontroller. The microcontroller senses
the temperature with a cold water reservoir probe and cycles the
compressor relay on and off.
BACKUP SYSTEMS
Backup systems within the Medi-Therm II machine limit the
temperature of water exiting the machine to specified ranges in
the event of a failure of the control system including the main
controller:
• BACKUP SYSTEM I (PIC Microcontroller and probe)
The first backup system is independent of the main
microcontroller. It runs off its own power supply. It limits
the temperature of water exiting the machine in the
event of a failure of control circuitry (including the main
microcontroller). Using an overtemperature probe in the
same water path as the main microcontroller blanket
water probe, water temperature is sensed. When limit
temperatures are surpassed the PIC sends a signal to
trigger an analog REMOVE FROM USE NOW circuit,
which:
• shuts down the pump and heater
• lights the ALERT and the REMOVE FROM USE
NOW indicators; and,
• sounds the audible alarm.
In addition, if the main microcontroller is operational,
the compressor shuts down, the displays blank, and
the ALERT indicator and audible alarm turn on and off.
The power supply for this system is backed with a nickel
hydride battery to provide a minimum 10 minute audible
and visual POWER LOSS indication in the event of
power failure.
• BACKUP SYSTEM II (Thermostats)
The second backup system is independent of both the
main microcontroller and the first backup system. It
limits the temperature of water exiting the machine in
the event of a failure of control circuitry (including the
main microcontroller). This is accomplished using two
bimetallic thermostats. If either of these two thermostats
is actuated, they open the heater circuit directly and
trigger an analog REMOVE FROM USE NOW circuit
(separate from BACKUP SYSTEM I), which:
• shuts down the pump and heater
• lights the ALERT and the REMOVE FROM USE
NOW indicators; and,
• sounds the audible alarm.
In addition, if the main microcontroller is operational,
the compressor shuts down, the displays blank, and the
ALERT indicator and audible alarm turn on and off.
6.2 Theory, System Component Interconnections
See figure 14, p. 51 for base-to-head and control/display
board-to-power supply board connections; figure 25, p. 66 for the
system wiring diagram; figures 26-28, pp. 67-70 for the electrical
schematics; figures 22-24, pp. 60-65 for component layouts
and part designations; and figure 29, p. 71 for the system block
diagram.
CONTROL/DISPLAY BOARD, ALARM/BACKUP BOARD, AND
POWER SUPPLY BOARD
The Medi-Therm II machine uses three printed circuit boards (see
figure 14, p. 51):
• The control/display board contains the main
microcontroller circuits, the display circuits, and all other
low voltage control circuits.
• The alarm/backup board contains the BACKUP
SYSTEM I microcontroller circuits, POWER LOSS
indicator circuits and its own power supply.
• The power supply board contains the main
microcontroller power supply, the low voltage to high
voltage interface circuits, and the REMOVE FROM USE
NOW latching circuits.
The control/display board connects to the patient probe jack J1
via P2 at J2 and to the digital control assembly panel via P4 at
J4A. All other connections from the system’s peripheral devices
to the control/display board are made through the power supply
board.
A 26-pin cable connects the control/display board via P1 at J1 to
the power supply board via P3 at J4.
Five cables connect the components in the base of the machine
to the PC boards in the head (see figure 14, p. 51):
• A 9-pin connector P6 ties the blanket water probe
RT2, cold water reservoir probe RT1, flow switch S5,
and level switch S4 to the power supply board at J2 and
ultimately to the control/display board.
• A 12-pin connector P7 ties the high voltage devices
(pump, heater, hot solenoid valve SV2, cold solenoid
Theory of Operation
11

MTA6012CE Service ManualTheory of Operation
valve SV1, and refrigeration compressor relay K1 to the
interface circuits on the power supply board, as well
as thermostats S1 and S2 to the high voltage latching
circuitry on the power supply board, at J1 on the power
supply board.
• A 6-pin connector P5 connects transformer T1 housed
in the base to the power supply circuitry at J3 on the
power supply board.
• a 6-pin connector P11 connects the over-temperature
probe RT3 and auxiliary switch within the circuit breaker
CB1 (for sensing POWER LOSS) to the alarm/backup
board at J4.
• A chassis ground harness from the control/display
board and alarm/backup board connects to the chassis.
6.3 Theory, Main Microcontroller Power Supply
See figure 25, p. 66 for the system wiring diagram; figures 26-28,
pp. 67-70 for the electrical schematics; figures 22-24, pp. 60-65
for component layouts and part designations; and figure 29, p. 71
for the system block diagram.
Power enters the Medi-Therm II machine through circuit breaker
CB1 to feed the refrigeration unit (through relay K1) and the
stepdown transformer T2. The output of T2 is fused with a 6.3
amp fuse located below the TB1 terminal block; see figure 19,
item 22. Stepped down voltage from T2 then enters the power
supply board at J1 to feed the hot solenoid valve, cold solenoid
valve, heater and pump triacs, the high voltage latching circuits
and transformer T1.
Power to drive the low voltage circuits on the control/display board
is derived from the machine’s main microcontroller power supplies
which reside entirely on the power supply board. The transformer
T1 output is rectified and filtered to generate unregulated positive
and negative voltages. Q5, D1, L1 and associated components
are configured as a DC to DC switching regulator in a buck
configuration yielding a nominal output of +5.3 volts DC. Q6 is a
linear regulator with a nominal output of plus twelve (+12) volts
DC, while Q7, also a linear regulator, delivers a nominal output of
minus twelve (-12) volts DC.
6.4 Theory, Machine Functions
See figure 25, p. 66 for system wiring diagram; figures 26-28, pp.
67-70 for the electrical schematics; figures 22-24, pp. 67-70 for
component layouts and part designations; and figure 29, p. 71 for
the system block diagram.
The main microcontroller U37 is fully dependent on the code
stored in the U31 EPROM. When the machine is on, the main
microcontroller continually cycles through its main program loop
to perform the following:
• Thermistor output measurement (see section 6.4.1)
• Digital control panel input (section 6.4.2)
• Display update (section 6.4.3)
• Peripheral input (section 6.4.4, p. 13)
• Blanket/Patient temperature control (section 6.4.5, p. 13)
• Cold water reservoir temperature control (section 6.4.6,
p. 14)
Backup water temperature limiting is achieved independently of
the microcontroller. See section 6.4.7, page 14.
6.4.1 Thermistor Output Measurement
Temperature measurement is achieved using 400 series
thermistor beads located in the blanket water path (blanket water
probe RT2), the cold water reservoir (cold water reservoir probe
RT1), and in the patient via the patient probe jack J1.
The main microcontroller connects each of the three beads to the
current source circuitry (U38 and associated components) using
demultiplexor U49. At the same time, the resulting output voltage
created by the current through the thermistor is presented to an
amplifier circuit (U39 and associated components) via multiplexor
U50. The amplified voltage is then applied to a voltage-to-
frequency converter U24. A frequency up to 100kHz is presented
to port pin P3.5 of the microcontroller. The microcontroller
converts the incoming frequency to a temperature value.
At regular intervals two compensation resistors R13 and R12
are also processed in the same manner. These compensation
resistors are precision resistors with values at each end of the
probe temperature range of 0°C to 50°C. The values from the
precision resistors are used to compensate for circuit drift.
6.4.2 Digital Control Panel Input
User input is entered via a digital control panel. The input from the
buttons is decoded by U45. The “data available” line of U45 is tied
to the main microcontroller port pin P3.3. When a button press is
decoded and debounced by U45, the “data available” line goes
high and the microcontroller responds by inputting the decoded
value.
6.4.3 Display Update
For display of measured and set point temperatures, 7 segment
LED displays are utilized:
• The set point display is driven by driver chip U48. The
main microcontroller interfaces to it via the data bus at
addresses 0FFF8H, 0FFF9H, 0FFFAH, 0FFFBH.
• The patient display is driven by driver chip U6. The
main microcontroller interfaces to it via the data bus at
addresses 0FFF4H, 0FFF5H, 0FFF6H, 0FFF7H.
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MTA6012CE Service Manual Theory of Operation
• The blanket display is driven by driver chip U5. The
main microcontroller interfaces to it via the data bus at
addresses 0FFECH, 0FFEDH, 0FFEEH, 0FFEFH.
All alarm and status indicators are lit by LED bars driven by
inverter/driver IC’s:
• The alarm latch U53 is the interface between the main
microcontroller and the ALERT, ADD WATER, CHECK
PATIENT, CHECK FLOW, REMOVE FROM USE
NOW, and SELECT drivers via the data bus at address
0FFBFH. A high signal written to the latch by the main
microcontroller activates the individual inverter/drivers
to light the corresponding indicator.
• The mode display latch U54 is the interface between
main microcontroller and the IN-TEMP, COOL, HEAT,
PATIENT CONTROL, BLANKET CONTROL, and
MONITOR ONLY drivers via the data bus at address
0FFDFH. A high signal written to the latch by the main
microcontroller activates the individual inverter/drivers.
• The control latch U51 is the interface between the
main microcontroller and the two leader light drivers
via the data bus at address 0FF7FH. When this latch
is selected, a low signal on the data line from the
microcontroller causes a high signal on the latch output.
Therefore, these two LED bar displays are “active low” in
the eyes of the microcontroller in contrast to all the other
LED bar displays of the machine.
The audible alarm located on the alarm/backup board is driven
by a high signal from the control latch U51 (from the main
microcontroller via the data bus at address 0FF7FH) or a high
RFU IN signal from Q10 on the power supply board or a high
signal from the PIC microcontroller on the alarm/backup board. A
low data line signal from the main microcontroller to U51 causes a
high signal on the latch output. Therefore, the alarm is “active low”
in the eyes of the main microcontroller. NOR gate U40, driver U26
and transistor Q1 work in conjunction to activate the alarm.
6.4.4 Peripheral Input
The input buffer U55 is the interface between the main
microcontroller (via the data bus at a “read” address of 0FFFEH)
and the input signals from the flow switch S5 and the level switch
S4 (which travel from the base through the power supply board),
the probe presence switch within the patient probe jack J1, and
the service mode button S3 on the control/display board. The
lines to the buffer from the peripheral devices are default high (via
pull-up resistors).
The level switch S4 will pull its buffer input line low when it senses
a sufficient water level.
The flow switch S5 will pull its buffer input line low when it senses
sufficient flow.
The probe presence switch within J1 will pull its buffer input line
low when it senses the presence of the patient probe.
Pressing the service mode switch S3 on the control/display
board will pull its buffer input line low. Pressing this switch while
powering up the machine will cause the machine to execute code
which implements several service modes for troubleshooting use.
6.4.5 Blanket/Patient Temperature Control
If the machine is in BLANKET CONTROL mode, the blanket water
temperature as sensed by the blanket water probe is used as
the feedback signal for controlling the water temperature to the
BLANKET CONTROL mode set point temperature.
If the machine is in PATIENT CONTROL mode, the patient
temperature as sensed by the patient probe connected to the
patient probe jack is used as the feedback signal for controlling
the patient temperature to the PATIENT CONTROL mode set
point temperature. The machine accomplishes this by adjusting
the water temperature.
For water temperature control, the main microcontroller control
system outputs a pulse train to each solenoid valve. The pulse
train to the hot solenoid (and also heater) is the complement
of the pulse train to the cold solenoid. The pulse train duty
cycle depends on the magnitude and sense of the control
signal calculated by the main microcontroller. That is, while the
solenoids are each either on or off, the ratio of on time to off time
is proportional to the calculated control signal amplitude. For large
differences between set point and probe temperatures, the output
to each solenoid valve will be either on or off. For differences
approaching zero, the outputs to the solenoid valves (and heater)
will switch on and off, with the on and off times automatically
adjusted to maintain a probe temperature equal to the set point.
The circulating pump is energized whenever the unit is in
PATIENT CONTROL or BLANKET CONTROL modes.
The control latch U51 on the control/display board is the interface
between the main microcontroller (via the data bus at address
0FF7FH) and the peripheral drivers on the power supply board.
Interface circuitry on the power supply board consists of U1, U2,
U7, U8, Q3, Q4, Q8, Q9, and associated components. U1, U2,
U7, and U8 are optically coupled triac drivers used to control
their respective triacs (Q3, Q4, Q8, and Q9); these combinations
provide electrical isolation between the low voltage main
microcontroller control circuits and the line voltage circuits.
The heater, pump, hot solenoid valve, and cold solenoid valve
are individually controlled by the main microcontroller through
latch U51 on the control/display board. A high signal on the data
line from the main microcontroller causes a low signal on the
appropriate output line of U51 which then sinks current from the
power supply board to activate the peripheral devices.
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MTA6012CE Service Manual
Pin 11 of U51 on the control/display board and U8 and Q9 of the
power supply board control the cold solenoid valve while pin 9
of U51 on the control/display board and U7 and Q8 of the power
supply board control the hot solenoid valve. Pin 8 of U51 on the
control/display board and U2 and Q4 of the power supply board
control the circulating pump. Pin 7 of U51 on the control/display
board and U1 and Q3 of the power supply board control power to
the heater.
6.4.6 Cold Water Reservoir Temperature Control
The control latch U51 on the control/display board is the interface
between the main microcontroller (via the data bus at address
0FF7FH) and the refrigeration compressor relay driver on the
power supply board. A high signal on the appropriate data line
causes a low signal at pin 6 of U51 on the control/display board,
which then activates Q12 on the power supply board. Q12 on the
power supply board is the interface between the control/display
board and the coil of the power relay K1 located in the machine
base. The main microcontroller switches power through the relay
to the refrigeration compressor at cut-out and cut-in temperatures
of 3.3°C and 5.8°C. These temperatures are sensed by the cold
water reservoir probe RTl located in the water reservoir. (See
figure 16, p. 53.) Control of the cold water reservoir temperature
takes place whenever the machine is on.
6.4.7 Backup Water Temperature Limiting
Water temperature limiting is provided by two systems; Backup
System I and Backup System II.
Backup System I consists of a PIC microcontroller residing on the
alarm/backup board, the over-temperature probe RT3 located in
the base, and one of the REMOVE FROM USE NOW latching
circuits on the power supply board.
Backup System II consists of two REMOVE FROM USE NOW
latching circuits and two fixed non-adjustable temperature limit
thermostats, S1 and S2 located in the base.
6.4.7.1 REMOVE FROM USE NOW Latching Circuits
The power supply board includes two REMOVE FROM USE
NOW latching circuits made up of U3, U4, U5, U6, U9, U10, D2,
D3, Q1, Q2, and their interconnecting components. Under normal
circumstances, Q1 and Q2 are kept turned on by the action of R7,
C10, and D4 and R5, C15, and D5 to complete the conduction
path for the heater and pump.
6.4.7.2 Backup System I
The PIC microcontroller has its own power supply on the alarm/
backup board which is independent of the main microcontroller’s
power supply circuits. Transformer T1 output is rectified and
filtered to generate unregulated positive voltage. Q1 is a linear
regulator with a nominal output of +5.0 volts. Interface circuitry
for Backup System 1 consists of Q2 and R1 on the alarm/backup
board and optical coupler U4 on the power supply board which is
powered by the independent power supply of the alarm/backup
board.
The PIC microcontroller repetitively compares the resistance of
the RT3 over-temperature probe (which is a 400 series thermistor
in the blanket water flow path) with fixed precision resistor
R11. When the blanket water temperature (as sensed by RT3)
surpasses the temperature represented by the fixed resistor
(see section 3.2, Thermal Specifications, page 3, for the RT3
high temperature limit) the PIC commands a REMOVE FROM
USE NOW shutdown condition via optical coupler U4 on the
power supply board. It also signals the audible alarm directly
with a continuous tone (regardless of the main microcontroller
operational status). These commanded signals by the PIC
microcontroller will remain until the machine is powered down.
U4 prevents Q1 from turning on so full line voltage will appear
between J1-2 and J1-3. In this case, U5 and U10 will be turned
on by the action of R4, D3, and associated parts while U3 and
U9 will be turned on by the action of R6, D2, and associated
parts. U5 prevents Q2 from turning on and U3 prevents Q1
from turning on even if the PIC command signal is removed. The
output of either U9 or U10, through buffer Q10, signals the main
microcontroller that a REMOVE FROM USE NOW condition has
resulted. Thus, should the PIC microcontroller sense an over
temperature condition, the heater and pump are shut off and the
main microcontroller is notified.
6.4.7.3 Backup System II
If the blanket water falls into the low temperature limit range,
S1 will open. If the blanket water temperature rises into the
high temperature range, S2 will open (see section 3.2, Thermal
Specifications, page 3, for the high and low temperature limits).
When either of these thermostats opens, it directly interrupts the
circuit and shuts off the pump and heater; at the same time, full
line voltage will appear between J1-2 and J1-3. In this case, U5
and U10 will be turned on by the action of R4, D3, and associated
parts while U3 and U9 will be turned on by the action of R6,
D2, and associated parts. U5 prevents Q2 from turning on and
U3 prevents Q1 from turning on even if the open thermostat(s)
closes again. The output of either U9 or U10, through buffer Q10,
signals the main microcontroller that a REMOVE FROM USE
NOW condition has resulted. Thus, should either thermostat
(S1 or S2) trip, the heater and pump are shut off and the main
microcontroller is notified.
6.4.7.4 Both Backup System I and II
On the control/display board, a high signal from Q10 of the power
supply boards feed drivers U52 to light the REMOVE FROM
USE NOW LED, feeds driver U11 to light the ALERT LED, and
feeds NOR gate U40 to drive the audible alarm located on the
alarm/backup board. All this is done independent of the main
Theory of Operation
14

MTA6012CE Service Manual
microcontroller. The same signal is sent to port P3.2 of the
microcontroller through C1, R1, and driver U11.
6.4.7.5 If The Main Microcontroller Is Nonoperational
If the main microcontroller is nonoperational at the event of a
signal from Q10 of the power supply board, the user is notified
of the REMOVE FROM USE NOW condition by the fact that all
the above mentioned indicators are on continuously. In addition,
the separate redundant circuits on the power supply board, each
triggered by either of the thermostats, or one triggered by the
PIC microcontroller, insure that the pump and heater remain off
even if the thermostat closes again or the PIC command signal is
lost. The REMOVE FROM USE NOW condition remains latched
and can be cleared only by an operator intervention in the form
of turning the machine circuit breaker off. If upon machine turn
on the fault condition still exists, the REMOVE FROM USE NOW
condition will recur.
6.4.7.6 If the Main Microcontroller is Operational
If the main microcontroller is operational at the event of a high
signal from Q10 of the power supply board (originating from
BACKUP SYSTEM I or BACKUP SYSTEM II), the signal at
P3.2 causes the main microcontroller to shut off the 7 segment
displays, flash the ALERT LED and light the REMOVE FROM
USE NOW LED, toggle the audible alarm, store the appropriate
RFU (Remove From Use) code indicating the reason for the
shutdown, turn off the heater and pump triacs Q3 and Q4, turn
off the solenoid triacs Q8 and Q9, and turn off the compressor
transistor Q12. (Separate machine service modes allow for
viewing the RFU code and for debugging problems. See section
8.0.)
The process of turning off the heater and pump triacs Q3 and Q4
by the main microcontroller removes power from the REMOVE
FROM USE NOW circuitry on the power board which then allows
the indicators on the control/display board to toggle under main
microcontroller control.
Note: The audible alarm will be a continuous tone
for an over temperature condition sensed by
BACKUP SYSTEM 1 regardless of the operational
status of the main microcontroller since the PIC
microcontroller puts out a continuous signal to the
audible independently which does not get reset
and which overrides any pulsing of the audible the
main microcontroller may perform.
The shutdown condition by the main microcontroller program will
remain until the machine is powered down. If, upon machine turn
on, the fault condition still exists, power replaced to the REMOVE
FROM USE NOW circuits on the power supply board when a
mode is selected (or automatically every 60 seconds in standby
mode) will cause the REMOVE FROM USE NOW condition to
recur.
6.4.7.7 Other REMOVE FROM USE NOW Shutdown
Conditions
If during normal operation the main microcontroller senses
internal problems, it will cause a machine shutdown condition
as in 6.4.7.6. As a precaution, it also sends an output signal
from port pin P3.4 through U40 on the control/display board,
to command, via Q11 and U6 on the power supply board a
REMOVE FROM USE NOW shutdown condition of the latches.
The appropriate RFU (Remove From Use) code for the shutdown
will be stored. See section 8.0.
6.4.8 Power Loss
The PIC microcontroller also provides the POWER LOSS
detection function. The Q1 linear regulator is provided voltage
also from an 8.4V nominal nickel metal hydride battery when the
auxiliary switch of the circuit breaker CB1 is closed (indicating the
circuit breaker is in the on position) and the main microcontroller
power supply circuits are not powered. The PIC microcontroller
detects this POWER LOSS condition via the optical coupler U3
which is tied to the main microcontroller power supply circuits.
6.4.9 Battery Charging
When the main microcontroller power supply circuits are powered
and the auxiliary switch of the circuit breaker CB1 is closed
(indicating the circuit breaker is in the on position), the battery is
trickle charged through R3 on the alarm/backup board.
6.4.10 Detection of Operational Backup System 1
The PIC microcontroller provides the 1 second power-up tone
for the machine. This can be used by the user to ascertain
whether the PIC microcontroller is operational. But, whenever the
machine is on the PIC microcontroller also creates a 0.15 second
on, 0.15 second off square wave pulse which is fed to the main
microcontroller via optical coupler U4 on the alarm/backup board.
The main microcontroller constantly monitors for this signal via
the CONN_SENSE line. If the pulse is not there or if it is not
correct, the main microcontroller shuts the machine down with a
REMOVE FROM USE NOW condition because this indicates that
the alarm/backup board has either been disconnected or the PIC
is not operational.
Theory of Operation
15

MTA6012CE Service Manual
7.0 Functional Check, Safety Inspection, and
Preventive Maintenance
7.1 Receiving Inspection Procedures
CONCEALED DAMAGE
After unpacking the Medi-Therm II machine, inspect the machine
for concealed damage. Save all packing material and carefully
describe or photograph the damage. Notify the carrier at once and
ask for an inspection (in writing). Failure to do this within 15 days
may result in loss of claim.
Before placing the Medi-Therm II machine into service, remove
the three compressor shipping braces (see p. 72, fig. B), attach
the power cord (p. 57), fill the reservoir with distilled water (p.
3 and p. 7), make sure the power loss indication works (e), p.
18), and perform a Functional Check and Safety Inspection (pp.
17-21).
7.2 Cleaning and Storage Procedures
FLUID SYSTEM
Use distilled water to retard algae growth and mineral buildup.
Change the distilled water monthly or more often depending upon
use.
The water circulation system, including blankets, should be
cleaned every month to retard algae growth.
To clean the fluid system, drain the machine and prepare an
algaecidal solution according to manufacturer’s instructions.
Use AirKem A-33 or equivalent. Add the solution to the machine,
attach blankets, set the machine in BLANKET CONTROL mode
to a setpoint temperature of 27°C and circulate the solution for
12 hours. Drain the solution and refill the machine with distilled
water. Algaecide solution may be readded to the water and left in
the machine in the recommended concentration to further retard
algae growth.
• Do not exceed proper algaecidal solution concentration.
Excessive algaecide may cause foaming, which can
damage the circulating pump.
• Do not use bleach (sodium hypochlorite). Bleach will
damage the heating element in the machine, which
could result in excessive leakage current.
COMPRESSOR
Dirt that has accumulated on the condenser coils and cooling fins
within the machine will reduce the efficiency of the compressor
and should be removed with a vacuum cleaner or compressed air
hose. This will require removal of the rear baffle assembly. This
should be checked monthly or more frequently depending upon
use. See figure 18, p. 55.
CAUTION
PUMP
Pump motor should be oiled once a year with 3-4 drops of general
purpose motor oil in the locations identified on the pump label.
7.2.1 Machine Cleaning
Users should not use cleaning or decontamination
methods different from those recommended.
To clean the external surfaces of the machine and connector
hose, use a nonabrasive cleaning solution (such as warm, soapy
water) and a clean cloth. Wipe or air dry. Apply a disinfectant
such as 10% chlorinated bleach solution (chlorinated bleach with
5.25% sodium hypochlorite) to the external surfaces and allow to
dry.
Do not use bleach within the machine.
7.2.2 Blanket Care
• Do not store filled blankets. Algae growth may occur
inside.
• Do not use a blanket if severe algae buildup occurs.
• Do not expose blankets to temperatures over 65°C.
REUSABLE BLANKETS
To clean inside reusable blankets, attach the blankets to the
machine and follow instructions for section 7.2, Cleaning and
Storage Procedures, Fluid System.
To clean the outside of a reusable blanket:
1. Manually clean both sides of the blanket on a flat surface
with warm water, a mild commercial detergent, and a sponge
or cloth.
2. Thoroughly rinse with clean water for 30 seconds.
3. Air dry or wipe with a clean cloth.
4. Apply a disinfectant such as a 10% chlorinated bleach
solution (chlorinated bleach with 5.25% sodium hypochlorite)
to both sides of the blanket.
5. Allow to air dry. Solution contact time is what makes
disinfection effective.
NOTE: Excess solution pooled in the buttons can be
removed with a clean, dry cloth.
CAUTION
Functional Check, Safety Inspection, and Maintenance
16
CAUTION

MTA6012CE Service Manual
6. Loosely roll up the blanket and store for next use.
Reusable blankets can be cleaned and reused so long as
they do not crack or leak.
7.2.3 Probe Care
REUSABLE PROBES
For cleaning, disinfecting, and sterilizing reusable Gaymar probes
(or equivalent YSI 400 series reusable probes), refer to the
instructions provided with the probe.
DISPOSABLE PROBES
Gaymar disposable probes should be discarded after use.
7.2.4 Probe Check Well Care
The PROBE CHECK WELL should be cleaned with a small
tubular brush as outlined in section 7.2.1, Machine Cleaning.
7.2.5 Quick-Disconnects
The quick-disconnects joining the connector hose to the machine
may become difficult to engage. This problem can be prevented
by periodically applying a silicone base or light machine oil to the
outside of the male connector prior to engagement.
Figure 6—Probe Check Well
probe
check
well
protective
sheath
probe
17
7.3 Functional Check and Safety Inspection
To assure the optimum performance, dependability and safety, the
following should be performed each year, or as specified in the
facility’s preventive maintenance program.
An Inspection Form is provided at the end of this section to
facilitate and document the inspection process. Lower case letters
preceding the subheadings within section 7.3 correspond to the
lines on the Inspection Form.
Always perform the Functional Check and Safety
Inspection after making repairs and before returning the
Medi-Therm II machine to patient use.
Improper repair may result in death or serious
injury, equipment damage, or malfunction.
REQUIRED TEST EQUIPMENT
The following test equipment (or equivalent) is required to perform
the preventive maintenance/functional check procedures:
• GAYMAR TPT9 Flowmeter/Temperature Tester †
• GAYMAR TFC1 Mercury Thermometer (±1°C
accuracy); -2°C to +52°C range †
† As an alternative to the above TPT9 and TFC1 test
equipment, you may use:
 a liquid flow meter with a measurement range of 10
to 75 liters per hour and an accuracy of ± 5% of full
scale, and
 an inline fluid temperature sensor with a measure-
ment range of 0 to 50°C and an accuracy of ± 1°C.
• GAYMAR DBK35CE Blanket Connector Hose
• GAYMAR PRK2 Patient Temp Simulator Kit, or a
Precision Decade Box (0-10K ohms, 0.2%
accuracy, 1 ohm increments)
• GAYMAR DHP901CE or DHP813CE Hyper/
Hypothermia Blanket
• Ground Resistance Checker
• Current Leakage Tester
• Static Control Wrist Strap
Risk of electrical shock when parts are electrified.
WARNING
DANGER
Functional Check, Safety Inspection, and Maintenance

MTA6012CE Service Manual
Cycle the switch on and off several times. The switch should have
a positive engagement (“click”) for the OFF and ON positions.
e) POWER LOSS Indication
Test to insure that the POWER LOSS indication works. With the
power cord unplugged, turn the circuit breaker to the ON position.
The POWER LOSS indicator should flash and the audible alarm
should sound continuously. If it doesn’t, the battery may have
self-discharged due to nonuse. While the machine operates it
trickle charges the battery, which powers this function. Operating
the machine for four hours will recharge the battery sufficiently to
allow 10 minutes of POWER LOSS INDICATOR operation. If the
battery does not recharge, replace it. Dispose of battery. See the
alarm/backup board parts list (p. 65).
Replace with a rechargeable battery only (type V7/8H-
-Nickel Hydride, 8.4 V nominal, 150 mAh). Otherwise,
battery damage may occur.
f) Condition of Lights and Alarm
Plug in the Medi-Therm II machine and turn it on. Press and hold
the TEST LIGHTS button. The right and left halves of the display
panel should light and blank alternately (along with the audible
alarm). The three status legends (HEAT, IN-TEMP, and COOL),
the ALERT legend and its four (triangular) indicators, and the
three mode legends and SELECT heading should be lit. The three
temperature displays should indicate “888”, “888.8”, and “888.8”.
The two lines connecting SET POINT to both the BLANKET
TEMPERATURE and PATIENT TEMPERATURE display should
be lit. The audible alarm should sound. Replace any LED’s which
do not light.
g) Flow
To measure the machine’s flow rate and check the flow switch
actuation, perform the following:
1. Fill machine with distilled water until green band on float
stem is fully visible.
2. Connect the test setup shown in figure 17A/B, p. 54.
3. Turn machine on. Set machine in BLANKET CONTROL
mode.
4. Increase the temperature set point to light the HEAT status
light. Note the flow rate.
5. Decrease the temperature set point to light the COOL status
light. Note the flow rate.
6. The flow rate in both modes should exceed 60.6 liters per
hour.
WARNING
Functional Check and Safety Inspection
Follow the following procedures carefully, paying particular
attention to test setups. Any deviation from the setups,
procedures, or test equipment may result in incorrect or
misleading results.
Before making any repairs, be sure to recheck your test setup,
procedure, and test equipment.
a) Condition of Chassis
The following inspections should be performed:
1. The chassis should be clean and relatively free of rust and
corrosion.
2. Exterior screws should be tight
3. Legends, markings, and operator instructions should be
legible.
4. Dirt that has accumulated in vents and cooling fins within
the machine should be removed with a vacuum cleaner or
compressed air hose. This will require removal of the rear
baffle assembly.
5. Check that the casters are tight and functioning properly.
6. The quick-disconnect fittings on the machine may become
stiff and difficult to engage. If so, apply a silicone-base
lubricant to the inside of the machine fittings and the outside
of the blanket connector.
7. Clean the Probe Check Well according to the procedure
described in section 7.2.4, p. 17.
8. Inspect the fluid system for debris and any sign of
algae growth. Clean according to Cleaning and Storage
Procedures, Fluid System (section 7.2, p. 16).
b) Attachment Plug
Examine the attachment plug on the line cord to be sure that it is
in good condition.
c) Power Cord and Cord Retainer
Make sure the detachable power cord is an approved cord set
(see 3.4, p. 5). Examine the power cord along its entire length for
physical damage, such as cuts or cracked insulation. A damaged
power cord should be replaced rather than repaired. Check that
the cord retainer is installed and secure. Do not operate without
the cord retainer.
d) Circuit Breaker
A worn out circuit breaker can be responsible for intermittent
shutoffs, with no other apparent indications of failure.
Examine the physical condition of the circuit breaker, paying
particular attention to the push-on terminals at the rear of the
breaker. Terminals should be snug. Replace breaker and/or
terminals if there is discoloration or any indication of heating.
18