Medi-Therm II Service Manual July 1999

1.0

Machine Precautions

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MTA6012CE Service Manual Safety Precautions

Review the following safety precautions prior to testing the Medi-Therm II machine:

DANGER Risk of electric shock. Refer servicing to qualified medical equipment service personnel.

WARNING • 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.

CAUTION 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.

1

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

MTA6012CE Service Manual 2.4

Return Authorization

Please contact your local dealer.

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Repairs/Warranty

3.0

Specifications

3.1

Physical

Specifications

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MTA6012CE Service Manual

P hy sical S pecif icat ions

3.2

M odel

M TA6012CE

Dim ensions

94 cm high x 48 cm deep x 36 cm w ide

Weight

73. 9 kg (f ull); 66. 2 kg (em pt y )

Norm al Reserv oir O perat ing Volum e

9. 5 lit ers dist illed w at er

O perat ing Am bient Tem perat ure Range

15. 6° C T O 32. 2° C

Pow er Loss I ndicat or Bat t ery

8. 4V NiM H

Ref rigerant

HFC-134a, 0. 326 kg

Fuse (st epdow n t ransf orm er)

5 m m x 20 m m T, 6. 3 A, 250 V, L

Thermal Therm al S pecif icat ions High Tem perat ure Lim it s Fixed Backup Sy st em 1--O v ert em perat ure probe RT3

41. 4° C t o 43. 6° C (M achine w ill go int o a REM O VE FRO M USE NO W shut dow n condit ion and t he alarm w ill be on. )

High Tem perat ure Lim it s Fixed Backup Sy st em 2--Therm ost at S2

44° C t o 49° C (M achine w ill go int o a REM O VE FRO M USE NO W shut dow n condit ion and t he alarm w ill be on. )

Low Tem perat ure Lim it s Fixed Backup Sy st em 2--Therm ost at S1

-3. 0° C t o 2. 5° C (M achine w ill go int o a REM O VE FRO M USE NO W shut dow n condit ion and t he audible alarm w ill be on. )

Add Wat er Alert Act uat ion

Less t han 7. 6 lit ers of w at er in t he cold reserv oir

Check Pat ient Alert Act iv at ion Tem perat ure (w henev er probe is used)

Below 29° C or abov e 40° C

M achine Ceases Therapy (w henev er probe is used)

Below 29° C or abov e 45° C

Pat ient Tem perat ure Cont rol Range f or P A T I E N T C O N T R O L m ode

30° C t o 39° C

Blanket Tem perat ure Cont rol Range f or B LA N K E T C O N T R O L m ode

4° C t o 41° C

Flashing Tem perat ure Display (w it h set point 30° C or great er)

• Blanket M ode: Act uat es w hen act ual t em perat ure is not w it hin 0. 5° C of set point 4 hours af t er pow erup, 4 hours af t er a set point change, or 10 m inut es af t er t he f irst inst ance of t he act ual t em perat ure becom ing equal t o t he set point . • Pat ient M ode: Act uat es w hen act ual t em perat ure is not w it hin 0. 5° C of set point 4 hours af t er pow erup or 4 hours af t er a set point change.

3

3.2

MTA6012CE Service Manual

Thermal (continued)

COOLDOWN RATE (typical)

45 40 35 30 25 20 15 10 5 0

Temperature (°C)

Temperature (°C)

WARM-UP RATE (typical)

0

5

10

15

20

45 40 35 30 25 20 15 10 5 0

25

0

5

Figure 1—Typical warm-up rate (with full size blanket)

3.3

10

Figure 2—Typical cooldown rate (with full size blanket)

Performance P erf orm ance S pecif icat ions Patient Tem perature M easurem ent Accuracy

± 0.4° C (using Gay m ar disposable probe) ± 0.3° C (using Gay m ar reusable probe)

Display Accuracy

± 0.2° C

Display Resolution BLANKET WATER TEMPERATURE

1° C

Display Resolution PATIENT TEMPERATURE

0.1° C

Controller Accuracy BLANKET WATER TEMPERATURE

± 0.8° C

Controller Accuracy PATIENT TEMPERATURE

± 0.5° C

Flow *

60.6 liters per hour

* M inim um f low rat es t hrough a f ull size G ay m ar Hy per/ Hy pot herm ia Blanket

4

15

Time (minutes)

Time (minutes)

20

25

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Specifications

3.4

Specifications

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MTA6012CE Service Manual Electrical E lect rical S pecif icat ions

3.5

Current Leakage, Earth Neutral closed Neutral open

175 m icroam ps m axim um 125 m icroam ps m axim um

Current Leakage, Patient Probe Neutral closed Neutral open

100 m icroam ps m axim um 100 m icroam ps m axim um

Voltage

~220 V to ~240 V ± 10%

Frequency

50 Hz

Pow er Consum ption Capacity

1575 VA

Current

6A

Detachable Pow er Cord

Use only an International (harm onized) three-w ire cordset using cordage approv ed to HD-21. Conductor size is 1.00 m m ² (H05VVF3G1.00).

Regulatory Regulatory

3.6

M edical Dev ice Directiv e (93/42/EEC) Class IIA (indicated by CE m ark)

Classification Classification

• IEC 601-1 Class 1, grounded, not suitable for use in the presence of flam m able anaesthetic m ixture w ith air or w ith oxy gen or nitrous oxide. Not classified for protection against harm ful ingress of liquid.

• IEC 601-1-2, Class A, CISPR 11, em ission requirem ents. • IEC 601-2-35

5

4.0

Blankets/Accessories

Single Patient Use Blankets, Polymer with Nonwoven Fabric

MTA6012CE Service Manual 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] Reusable Probe Adaptor Cable (3 meters) for DP400CE Probe

REF DHP810CE

O.R. Table and General Use (64 cm x 163 cm)

REF DHP812CE

Pediatric General Use (56 cm x 84 cm)

REF ADP10CE

REF DHP813CE

Adult General Use (76 cm x 163 cm)

*

These Gaymar probes, adapters, and hoses should be used only with Gaymar Hyper/Hypothermia Machines.

Single Patient Use Blankets, All Polymer REF DHP901CE

Adult General Use (64 cm x 175 cm)

REF DHP902CE

Pediatric General Use (64 cm x 91 cm)

REF DHP903CE

Adult General Use (Narrow) (51 cm x 150 cm)

Single Patient Use Blankets, All Polymer with Nonwoven Fabric REF DHP911CE

Adult General Use (64 cm x 175 cm)

REF DHP912CE

Pediatric General Use (64 cm x 91 cm)

Reusable Blankets, Heavy Duty Polymer REF HP7010CE

Adult General Use (64 cm x 175 cm)

REF HP7020CE

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)

6

Figure 3—Disposable Probe/Reusable Adaptor Cable

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Blankets/Accessories

Water Fill Opening Lift cover. Fill unit with distilled water until green band on float is fully visible.

Medi-Therm II System

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MTA6012CE Service Manual

Patient Probe Jack Accepts patient probe plug connecting patient probe to machine. Use only Gaymar probes or equivalent YSI 400 series probes.

ON/OFF Switch (Circuit Breaker) Controls power to Medi-Therm II. 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 7

5.0

MTA6012CE Service Manual

Operator Control Panel

See figure 5, page 9.

MACHINE STATUS

HEAT indicates the machine is heating.

IN-TEMP indicates that the blanket or patient temperature is at the desired temperature setting.

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.

COOL indicates the machine is cooling. ADD WATER indicates the water reservoir is filled to less than the recommended level.

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.

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]

8

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Operator Control Panel

Operator Control Panel

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MTA6012CE Service Manual

Figure 5—Medi-Therm II Control Panel SELECT MODE

TEMPERATURE

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.

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 “t” or “s” 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 “t” or “s” 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

6.0

Theory of Operation, System

The Gaymar Medi-Therm II machine provides a means of regulating 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.

10

MTA6012CE Service Manual 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.

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Theory of Operation

Theory of Operation

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 11

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MTA6012CE Service Manual

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.

MTA6012CE Service Manual • 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)

• 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.

Backup water temperature limiting is achieved independently of the microcontroller. See section 6.4.7, page 14.

• A chassis ground harness from the control/display board and alarm/backup board connects to the chassis.

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.

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) 12

6.4.1

Thermistor Output Measurement

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-tofrequency 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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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.

Theory of Operation 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. 13

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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.

MTA6012CE Service Manual 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

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.

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).

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.

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.

6.4.7.1 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 14

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

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Theory of Operation

Theory of Operation

microcontroller. The same signal is sent to port P3.2 of the microcontroller through C1, R1, and driver U11.

6.4.7.7 Other REMOVE FROM USE NOW Shutdown Conditions

6.4.7.5 If The Main Microcontroller Is Nonoperational

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.

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.

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.

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. 15

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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.

MTA6012CE Service Manual

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 CAUTION

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 CAUTION

The water circulation system, including blankets, should be cleaned every month to retard algae growth.

• Do not store filled blankets. Algae growth may occur inside.

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 use a blanket if severe algae buildup occurs.

CAUTION • 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. 16

• 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.

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Functional Check, Safety Inspection, and Maintenance

6.

Functional Check, Safety Inspection, and Maintenance

Loosely roll up the blanket and store for next use.

7.3

Reusable blankets can be cleaned and reused so long as they do not crack or leak.

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.

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

Functional Check and Safety Inspection

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.

WARNING 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:

probe check well

•

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

protective sheath probe

§ an inline fluid temperature sensor with a measurement range of 0 to 50°C and an accuracy of ± 1°C. Figure 6—Probe Check Well

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.

•

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

DANGER Risk of electrical shock when parts are electrified. 17

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MTA6012CE Service Manual

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

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 selfdischarged 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).

WARNING 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.

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Functional Check and Safety Inspection

NOTE: If the unit has been completely drained, air can be trapped in the pump causing flow to be decreased. To clear the air, turn the unit off, wait approximately one minute, and start again from step 3.

Functional Check and Safety Inspection 2.

Connect the test setup shown in figure 17, p. 54.

3.

Turn machine on. Set in BLANKET CONTROL mode.

4.

Set the Temperature Setpoint to the various settings specified on the Inspection Form (fig. 7, p. 21), wait until the IN-TEMP LED comes on and the water temperature stabilizes, then record the measured temperature and that shown on the display. Verify that the recorded values are within the limits outlined on Inspection Form, item j.

To test the actuation of the level switch, perform the following:

k)

High Temperature Backup Trip Temperatures

1.

Fill machine with distilled water until green band on float stem is fully visible. The ADD WATER indicator should be off.

The following checks k1) and k2) should be performed in the order shown:

2.

Connect a DBK35CE hose to a supply fitting on the machine and direct the other end to a drain or gallon (4 liter) container.

3.

Turn machine on. Set machine in BLANKET CONTROL mode. Adjust the temperature set point to 4°C (COOL status light on).

4.

Allow water to drain until bobber has bottomed out on the drain screen (about 3 liters). The ADD WATER indicator should be lit and the audible alarm should sound.

5.

Refill machine with distilled water until the green band is fully visible. Verify that the ADD WATER indicator goes out.

7.

Kink the hose to stop the flow. The CHECK FLOW indicator should light, the ALERT indicator should flash on and off, and the audible alarm should sound.

h)

Level Switch Actuation

i)

Cold Water Reservoir Controller

k1) S2 High Temperature Thermostat Trip Temperature 1.

Fill machine with distilled water until the green band on float stem is fully visible.

2.

To test S2, RT3 will need to be disabled. This can be accomplished by disconnecting the alarm/backup board while the machine is operated in the service modes. Note:

3.

Unplug the power cord.

4.

Disconnect the 7-conductor cable harness connector P12 from the alarm/backup board. See figure 14, page 51.

5.

Disconnect the 6 conductor cable harness connector P11 from the alarm/backup board. See figure 14.

6.

Plug the machine in.

7.

Place the machine in service mode 3. Refer to section 8.1, Service Modes (p. 22, 24) for instructions.

8.

Run the machine for 5 minutes after the blanket water temperature has reached 41°C.

9.

Enter service mode 4 (see section 8.1, pp. 22, 25) from service mode 3. Mode 4 will cause the machine to heat up until S2 trips.

To check the cold water reservoir controller, 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. NOTE:

To minimize the test time for this test only, remove the blanket from the flow path shown in figures 17A/17B.

3.

Turn machine on and push the BLANKET CONTROL mode button.

4.

Set the Temperature Setpoint to 4°C.

5.

Verify that the machine can supply water anywhere within the 3°C to 6°C range as measured and that the compressor turns off one time. (This will take 15-30 minutes, depending upon room temperature and other conditions. The use of a blanket for this test can extend this time up to 60 minutes.)

j)

Blanket Water Temperature Controller and Display Test

To check the temperature controller, perform the following: 1.

Fill machine with distilled water until green band on float stem is fully visible.

In normal operating modes (non-service modes), a disconnected alarm/backup board will be detected and cause a REMOVE FROM USE NOW shutdown condition with a RFU code “P” stored.

10. Monitor the blanket water temperature. When the ALERT and REMOVE FROM USE NOW LED’s light (no audible alarm), the measured temperature should be within the limits listed on the Inspection Form. This indicates that S2 has tripped. Record the temperature at which S2 tripped on the Inspection Form. 11. Turn the machine off and unplug the power cord. Disconnect supply hose from TPT9/flowmeter and allow water to gravity drain into a container for approximately one minute. This will circulate cold water from the reservoir past the thermostat 19

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MTA6012CE Service Manual