Micro Medical ML3500 Service Manual

Microlab ML3500 ­ServiceManual

050-13 Iss. 1.0 June 2000

Contents

Exploded Isometric View............................................................................................3

System Overview.........................................................................................................4

Figure 1 .......................................................................................................................4

Transducer...................................................................................................................5

Figure 2 .......................................................................................................................5

Disassembling the MicroLab for Repairs..................................................................6

Reassembling the Microlab after repairs………………………………………………...6
Circuit Description

Circuit Overview ............................................................................................................. 7

Processor Control Section......................................................................................................................7

Address Bus............................................................................................................................................7

Ram Address Lines.................................................................................................................................7

Reset.......................................................................................................................................................7

Keypad....................................................................................................................................................7

Real Time Clock......................................................................................................................................8

Display.............................................................................................................................................8

Serial Interface........................................................................................................................................8

Battery Monitoring...................................................................................................................................8

Printer Driver...........................................................................................................................................8

Power Supply..........................................................................................................................................9

Printer Mechanism..................................................................................................................................9

Transducer Interface...............................................................................................................................9

Parts List....................................................................................................................10

Technical Support.....................................................................................................13

Fault Analysis............................................................................................................14

Circuit Diagrams........................................................................................................15

Circuit overview.....................................................................................................................................15

Processor Section.................................................................................................................................16

Power supply…………………………………………………………………………………………………...17
Printer Driver……………………………………………………………………………………………………18
PCB layer 1……………………………………………………………………………………………………..19
PCB layer 2……………………………………………………………………………………………………..20

2

Exploded Isometric View

Exploded Isometric View

Top
moulding

Printer
mechanism

Contrast
thumbwheel

Bottom
moulding

Screw

3

MicroLab - System Overview (Fig. 1)

The Micro Medical MicroLab is a data recording spirometer consisting of a microcomputer unit

(1) incorporating an LCD graphic display, data entry keypad, RS232 serial interface and all associated
circuitry. This is supplied with a digital volume transducer (2), disposable mouthpieces, transducer
holder (3) and mains adapter (4). The MicroLab is powered by internal rechargeable Nickel Cadmium
cells or by the mains adapter supplied (4).
When testing a subject the transducer is inserted into the holder which is plugged into the
microcomputer unit. The digital volume transducer is used to measure the subjects expired flow and
volume in accordance with the operating manual.

micro

lab

31 2
64 5

1

3

Micro

Medical

2

97 8

Del

0

4

Fig. 1

4

Transducer (Fig. 2)

The Micro Medical digital volume transducer consists of an acrylic tube with a vane positioned

between two swirl plates. The low inertia vane is attached to a stainless steel pivot which is free to
rotate on two jewelled bearings mounted at the centre of the swirl plates. As air is passed through the
transducer a vortex is created by the swirl plates which causes the vane to rotate in a direction
dependant upon the direction of air flow. The number of rotations is proportional to the volume of air
passed through the transducer and the frequency of rotation is proportional to the flow rate. The
transducer housing consists of a main body which contains a pair of light emitting diodes (LED’s) and
phototransistors. The transducer is fixed to the mouthpiece holder which pushes into the main body
and is captured by an “O” ring seal. The LED’s produce infra red beams which are interrupted by the
vane twice per revolution. This interruption is sensed by the phototransistors. The output from the
collector of each phototransistor will be a square wave with a phase difference between the two of +
or - 90 degrees depending upon the direction of flow.
There is no routine maintenance required for the transducer other than cleaning according to
the instructions in the operating manual.

Micro Medical Digital Volume Transducer

Volume proportional to the number of pulses
Flow proportional to the puse frequency

Rotating

vane

Volume = k X No. of pulses

Infra red

emitter

Infra red
detector

Swirl
plate

Flow = k / pulse period

Jewelled

bearing

5

Disassembing the Microlab for Repairs

1. Disconnect all mains power supplies

2. Remove paper roll and paper roll housing cover, and put to one side

3. Remove the battery cover / screw and retain.

We recommend that you use a Philip Number Zero screwdriver for the following
instruction.

4. Place the Microlab face down to remove the four screws in the lower moulding, and put the
screws to one side.

5. Turn the unit face up before easing the upper and lower mouldings apart.

6. Reconnect mains power supply

7. The Microlab is now ready for Fault Finding.

If you are not familiar with the operation of the Microlab please read the following section
in this manual ‘Circuit Description’ and use the Circuit diagrams at the back of this manual.

Reassembing the Microlab after Repairs

1. Disconnect the mains power supply

2. Position the top moulding over the bottom moulding and ensure that they mate up correctly. Also,
ensure that the keypad, LCD display flexi connectors and battery are connected and correctly
positioned.

3. Place the Microlab face down and insert the four screws into the lower moulding and secure to
the top moulding. Replace the battery cover and screw fixing.

4. Turn the unit face up and connect to the mains supply.

5. Turn the unit on and offer up the printer paper roll as explained in the operating manual. Replace
the paper cover.

6. The Microlab is now ready for operation.

6

Circuit Description

Overview (Drawing 050-01)

The microprocessor control circuit carries out the spirometry routines, monitors the transducer pulses
and keypad, and drives the display under the control of the program stored in the battery backed
RAM.
The power supply uses the mains adapter, internal Nickel-Cadmium (Ni-Cad) cells and an internal
lithium backup as its sources of energy. The supply provides 5 volts to the control circuit, -12 volts
supply for the display and RS232 driver circuit, 3 volts RAM backup, controls the charging current to
the Ni-Cad battery pack, and provides for battery management.
The microprocessor (U1) communicates with the real time clock (U9), the output latch (U8), and the
display under the control of the program, stored in the RAM (U7), using a multiplexed address and
data bus decoded by a data latch (U2). The RAM, which is used both for program storage and for
temporary data storage, has a memory map which is partitioned by the action of the PAL (U5) into
writable and non-writable areas.

Processor Control Section ( Drawing 050-02 )

Address bus

The microprocessor (U1) uses a multiplexed address bus. The lower order address lines are latched into U2
with the address strobe (AS).
The program for the microprocessor (U1) is stored in a 128kByte, battery backed static ram, (U7). As the
address space of the processor is limited to 64kBytes the ram address space is paged using a programmable
array logic device (U5). This device decodes address lines A1, A13, A14, A15, port lines PD5, PA4, control
line R/W, clock signal E, mode control lines MODA, MODB, and the external reset line to provide the
following outputs:

RAM address lines A15 and A16

Chip select lines (CS) for the display and latch (U8)
Write enable (WR) for display, latch, and RAM
Read enable (RD) for the display
Output enable (OE) for the RAM

Reset

The reset circuit consists of a single chip reset (U3) which holds the reset line (RES) low for 350ms after the 5
volt supply has reached the threshold voltage of 4.5 volts. The reset signal is applied to the microprocessor
(U1), display, programmable array logic device (U5), and the printer driver processor (U18).

Keypad

The keypad consists of a matrix of 14 keys (ON/OFF, 0 to 9, DELETE, and ENTER) together with a separate
paper feed key (PAPER). The matrix is read by successively asserting (5 volts) the columns of the matrix and
reading the state of the rows to determine which key has been pressed. The microprocessor asserts the columns
by writing to the latch (U8) and reads the rows directly on port E (PE4 to PE7). The diode (D10) prevents
current flowing from an asserted line of the latch to one at 0 volts in case of two keys on the same row being
depressed simultaneously. The resistors (R36 to R39) biases the PE4 to PE7 to 0 volts.

7

Real Time Clock

The real time clock (U9) is set by the processor during the factory set-up and should not require any
further adjustment. The processor communicates with the real time clock (RTC) with a serial interface
line to pin 5 of the RTC. The RTC is selected by the signal from pin 12 of the output latch (U8).

Display

The display is a custom graphic 128 by 64 dot LCD with in-built control circuitry. The contrast is
adjusted by varying the voltage on pin 3 between -4 and -12 volts with VR1. This potentiometer
varies the output of the voltage inverter, U12.

Serial interface

The microprocessor communicates with the integral printer and the external RS232 port using its
serial communications interface. Serial information from the microprocessor is switched to either the
printer driver or the external RS232 port under the control of the signal appearing on pin 9 of the latch
(IC5). This signal controls the switching logic of IC10 and IC8. The serial output from the
microprocessor, TXD, is applied to the input of IC10. Depending upon the state of the control signal,
the serial information will either pass through IC10 to the printer controller (IC17), or through the level
converter (TR4, and R22) to the external RS232 port.

Battery monitoring

The microprocessor contains eight, 8 bit analogue to digital converters. One of these, AN3 is used to
monitor the condition of the main supply (BAT1). The main supply is monitored at the input to the
logic 5 volt regulator (IC11) and the user will be alerted to a low battery condition when the voltage
falls below 6 volts. The voltage is divided by two with R8 and R9 to bring the voltage within the range
of the A/D converter (5 volts). AN3 also detects when the external power supply has been applied.
One end of R10 is pulled to 0 volts when the external supply is not applied and the voltage read on
the A/D converter will be up to 4 volts for a fully charged battery. With the external supply applied, the
voltage will rise above 5 volts.

Printer Driver (Drawing 050-04)

The printer driver uses a single chip micro-controller (U18) with on board program memory and RAM
to receive serial data from the microprocessor (U1) and control the printer mechanism. The printer
mechanism uses stepper motors to drive the print head and paper feed. Each stepper motor uses
four lines, driven sequentially. The order of in which the lines are driven determines the direction of
rotation. The thermal print head uses eight heater elements. The stepper motors and print head
signals are generated on port A and B (active high) of the micro-controller (U18). The signals pass
through two octal high current Darlington drivers (U16 and U17). Timing for Port A and B is derived
from an adjustable oscillator comprising of U19, R11, R32 to R35, C19, D9 and VR2. Adjusting VR2
varies the oscillator frequency and consequently the period for which the thermal elements are
energised. This in turn adjusts the print density. After the micro-controller is first reset, the print head
is driven to the left until the end switch is activated. The end switch consists of a normally closed pair
of contacts accessed at pins 1 and 2 of the printer connector, PL1. The end switch is detected by
PD5 on the micro-controller.

8

Power Supply

External power input, 5 volt logic and –12 volt supply (Drawing 050-03)

The external power input is applied through J5. Power is applied to the NI-Cad charging circuit and a
9 volt regulator (U14) through a reverse polarity protection diode, D5. The charging circuit consists of
R20, R27, TR3, and D2. These components are in a constant-current configuration and supply a
nominal 60mA to the Ni-Cad battery pack (BAT1). The charging indicator (LED1) is driven from the
output of U14 through R28. BAT1 is isolated from the circuit during charging by the action of D6,
which ensures that only the regulated output of IC7 can supply power when the external power supply
is connected. Power is supplied to the circuit when SW1 is switched, turning on the series pass
transistor TR5. TR5 can also be held on by the microprocessor through TR2 connected to PA5 of
IC1. This feature is used by the program to ensure integrity of data during periods of writing to the
RAM when the user may turn the unit off. The output of TR5 is filtered by R40 and C43 and used as
an unregulated power supply for IC26, IC29 and, IC27. All logic circuitry has 5 volts supplied from a
low drop-out regulator, IC11. The display requires a negative bias voltage and this is produced by the
–12 volt generator (IC12, C5, C6, D10, C7, and D7). Display contrast is adjusted by varying the
negative bias through the accessible VR1.

Printer mechanism supply

6 volts (VP) is supplied to the printer mechanism from the low drop-out, high current regulator, U20.
The input to IC16 comes from the Ni-Cad battery pack or external power supply through SW1.

Transducer interface

The supply to the two series LEDs inside the transducer housing is provided through TR7. This is
controlled by port pin PA3 of the processor and is only turned on during a spirometry manoeuvre to
conserve power. However, power is supplied to the transducer through D7 continuously when the
mains adapter is connected.
Inside the transducer housing the two phototransistors used to detect the interrupted infra-red beam
are in open collector configuration. The collectors are connected to pins 2 and 3 of SK2. The pull up
resistor for the phototransistor connected to pin 2 is provided by R18 and R21. The pull up resistor for
the other phototransistor is provided by R19 and R20. The signals from the phototransistors are
applied to the pulse timing input of the processor (pin 32) and a general purpose port pin 33 after
being squared up by the action of the schmitt inverters IC8 A and B. The rising edge of the signal
applied to pin 32 causes an interrupt to be generated in the processor. This interrupt is processed by
incrementing a pulse count, timing the period since the last pulse and by reading the state of pin 33.
The pulse count is used to determine the volume passed through the transducer since the start of the
test and the pulse period is used to determine the flow at each volume increment. The state of pin 33
at the time of the interrupt determines the direction of flow.

9

Parts List

U1 MC68HC11E1CFN MOTOROLA SM MICROCONTROLLER
U2 74HC573 SM OCTAL LATCH
U3 DS1233D-10 DALLAS ECONO RESET
U4 74HC14 SM HEX SCHMITT INVERTER
U5 PALCE16V8Z25PC AMD ZERO POWER CMOS PLD DIP PACKAGE
U5(S)
U6 74HC32 SM QUAD TWO INPUT OR GATE
U7 KM681000BLG/BLG-L SAMSUNG 1 MEG SM STATIC RAM 55-150ns ACCESS TIME
U8 74HC273 SM OCTAL D FLIP-FLOP
U9 PCF8583T PHILIPS SM CLOCK CALENDER WITH 256 BYTE RAM
U10 BU4S11 OR BU4S01 RHOM INDIVIDUAL SM CMOS GATE
U11 LM2931M-5.0 LOW DROP OUT 5 VOLT 100mA SM REGULATOR
U12 LT1054CS8 SM VOLTAGE CONVERTOR
U13 4093 SM QUAD NAND GATE
U14 LM2940T-9.0 LOW DROP OUT 9 VOLT 1 AMP REGULATOR
U15
U16 ULN2803LW 8 DARLINGTON SM ARRAY ALTERNATIVE TD62083AF
U17 ULN2803LW 8 DARLINGTON SM ARRAY ALTERNATIVE TD62083AF
U18 MC68HC705C9ACFN MOTOROLA OTP SM MICROPROCESSOR
U19 4069UB SM UNBUFFERED HEX INVERTOR
U20 LT1084CT LOW DROP OUT ADJUSTABLE VOLTAGE 5 AMP REGULATOR
R1
R2
R3
R4
R5
R6
R7
R8
R9
R10
R11
R12
R13
R14
R15
R16
R17
R18
R19
R20
R21
R22
R23
R24
R25
R26
R27
R28
R29
R30

20 PIN DIL SOCKET

DENSITRON INVERTOR

1M SM RESISTOR 0.125 WATT 5% SIZE 0805
1M SM RESISTOR 0.125 WATT 5% SIZE 0805
1M SM RESISTOR 0.125 WATT 5% SIZE 0805
100K SM RESISTOR 0.125 WATT 5% SIZE 0805
100K SM RESISTOR 0.125 WATT 5% SIZE 0805
100K SM RESISTOR 0.125 WATT 5% SIZE 0805
100K SM RESISTOR 0.125 WATT 5% SIZE 0805
100K SM RESISTOR 0.125 WATT 5% SIZE 0805
100K SM RESISTOR 0.125 WATT 5% SIZE 0805
100K SM RESISTOR 0.125 WATT 5% SIZE 0805
100K SM RESISTOR 0.125 WATT 5% SIZE 0805
100K SM RESISTOR 0.125 WATT 5% SIZE 0805
10K SM RESISTOR 0.125 WATT 5% SIZE 0805
10K SM RESISTOR 0.125 WATT 5% SIZE 0805
3K9 SM RESISTOR 0.125 WATT 5% SIZE 0805
8K2 SM RESISTOR 0.125 WATT 5% SIZE 0805
8K2 SM RESISTOR 0.125 WATT 5% SIZE 0805
1K SM RESISTOR 0.125 WATT 5% SIZE 0805
1K SM RESISTOR 0.125 WATT 5% SIZE 0805
1K SM RESISTOR 0.125 WATT 5% SIZE 0805
1K SM RESISTOR 0.125 WATT 5% SIZE 0805
1K SM RESISTOR 0.125 WATT 5% SIZE 0805
1K SM RESISTOR 0.125 WATT 5% SIZE 0805
1K SM RESISTOR 0.125 WATT 5% SIZE 0805
330K SM RESISTOR 0.125 WATT 5% SIZE 0805
33K SM RESISTOR 0.125 WATT 5% SIZE 0805
10 OHM SM RESISTOR 0.125 WATT 5% SIZE 0805
330 OHM SM RESISTOR 0.125 WATT 5% SIZE 0805
1K SM RESISTOR 0.125 WATT 5% SIZE 0805
120 OHM SM RESISTOR 0.125 WATT 5% SIZE 0805

10

R31
R32
R33
R34
R35
R36
R37
R38
R39
R40
RN1
VR1 T18 S/I S/B S/T 20KA PIHER 20K LINEAR POTENTIOMETER
VR2 3204X203P MEC CITEC SINGLE TURN 20K SM PRESET
C1
C2
C3
C4
C5 660-590(F) 1nF PHILIPS CERAMIC CAPACITOR SIZE 0805
C6 660-590(F) 1nF PHILIPS CERAMIC CAPACITOR SIZE 0805
C7 660-620(F) 10nF PHILIPS CERAMIC CAPACITOR SIZE 0805
C8 660-620(F) 10nF PHILIPS CERAMIC CAPACITOR SIZE 0805
C9 556-180(F) 47uF/16V SM ELECTROLYTIC CAPACITOR
C10 556-180(F) 47uF/16V SM ELECTROLYTIC CAPACITOR
C11 556-180(F) 47uF/16V SM ELECTROLYTIC CAPACITOR
C12 556-180(F) 47uF/16V SM ELECTROLYTIC CAPACITOR
C13 556-180(F) 47uF/16V SM ELECTROLYTIC CAPACITOR
C14 556-180(F) 47uF/16V SM ELECTROLYTIC CAPACITOR
C15 556-180(F) 47uF/16V SM ELECTROLYTIC CAPACITOR
C16 556-269(F) 22uF/35V SM ELECTROLYTIC CAPACITOR
C17 644-160(F) 0.1uF PHILIPS CERAMIC CAPACITOR SIZE 0805
C18 644-160(F) 0.1uF PHILIPS CERAMIC CAPACITOR SIZE 0805
C19 718-555(F) 820pF PHILIPS CERAMIC CAPACITOR SIZE 0805
C20 556-180(F) 47uF/16V SM ELECTROLYTIC CAPACITOR
C21 556-180(F) 47uF/16V SM ELECTROLYTIC CAPACITOR
C22
C23 644-160(F) 0.1uF PHILIPS CERAMIC CAPACITOR SIZE 0805
C24 644-160(F) 0.1uF PHILIPS CERAMIC CAPACITOR SIZE 0805
C25 644-160(F) 0.1uF PHILIPS CERAMIC CAPACITOR SIZE 0805
C26 644-160(F) 0.1uF PHILIPS CERAMIC CAPACITOR SIZE 0805
C27 644-160(F) 0.1uF PHILIPS CERAMIC CAPACITOR SIZE 0805
C28 660-620(F) 10nF PHILIPS CERAMIC CAPACITOR SIZE 0805
C29 644-160(F) 0.1uF PHILIPS CERAMIC CAPACITOR SIZE 0805
C30 644-160(F) 0.1uF PHILIPS CERAMIC CAPACITOR SIZE 0805
C31 644-160(F) 0.1uF PHILIPS CERAMIC CAPACITOR SIZE 0805
C32 644-160(F) 0.1uF PHILIPS CERAMIC CAPACITOR SIZE 0805
C33 644-160(F) 0.1uF PHILIPS CERAMIC CAPACITOR SIZE 0805
TR1 DTA114EK RHOM PNP DIGITAL TRANSISTOR SOT 23 PACKAGE
TR2 FMMT591 ZETEX PNP TRANSISTOR SOT 23 PACKAGE
TR3 2SB1189 RHOM PNP TRANSISTOR - MPT (SOT89) ALTERNATIVE 2SB1188
TR4 DTC114EK RHOM NPN DIGITAL TRANSISTOR SOT 23 PACKAGE
TR5 DTC114EK RHOM NPN DIGITAL TRANSISTOR SOT 23 PACKAGE
TR6 DTC114EK RHOM NPN DIGITAL TRANSISTOR SOT 23 PACKAGE
TR7 DTB113EK RHOM PNP DIGITAL TRANSISTOR SOT 23 PACKAGE

470 OHM SM RESISTOR 0.125 WATT 5% SIZE 0805
2K2 SM RESISTOR 0.125 WATT 5% SIZE 0805
22K SM RESISTOR 0.125 WATT 5% SIZE 0805
22K SM RESISTOR 0.125 WATT 5% SIZE 0805
150K SM RESISTOR 0.125 WATT 5% SIZE 0805
10K SM RESISTOR 0.125 WATT 5% SIZE 0805
10K SM RESISTOR 0.125 WATT 5% SIZE 0805
10K SM RESISTOR 0.125 WATT 5% SIZE 0805
10K SM RESISTOR 0.125 WATT 5% SIZE 0805
10K SM RESISTOR 0.125 WATT 5% SIZE 0805
10 SIL COMMONED RESISTOR NETWORK

33pF CERAMIC CAPACITOR SIZE 0805
33pF CERAMIC CAPACITOR SIZE 0805
33pF CERAMIC CAPACITOR SIZE 0805
33pF CERAMIC CAPACITOR SIZE 0805

15pF CERAMIC CAPACITOR SIZE 0805

11

TR8 FMMT491 ZETEX PNP TRANSISTOR SOT 23 PACKAGE

PSM PACKAGE. ALTERNATIVE SHINDENGEN D1F20

ARIES 4 INCH, 20 WAY, TYPE 172, FLAT PIN STAKED FLEX JUMPER

hr BATTERY WITH PCB MOUNTING PINS

TR9 FMMT491 ZETEX PNP TRANSISTOR SOT 23 PACKAGE
TR10 FMMT491 ZETEX PNP TRANSISTOR SOT 23 PACKAGE
LED 178-307 (F) T1/3mm ORANGE LED
D1 IMN10 ROHM 3 DIODE ARRAY - IMD PACKAGE
D2 IMN10 ROHM 3 DIODE ARRAY - IMD PACKAGE
D3 S1ZAS4 SHINDENGEN 1.2A DUAL SCHOTTKY DIODE
D4 BAT43W SCHOTTKY DIODE SOD123 PACKAGE (ALTERNATIVE BAT42W)
D5 S1NB20 SHINDENGEN 1A BRIDGE RECTIFIER
D6 DE5SC4M SHINDENGEN 5A DUAL SCHOTTKY DIODE
D7 1SR154-400 RHOM 1A DIODE ­D8 BAS19 SMALL SIGNAL DIODE SOT23 PACKAGE
D9 BAS19 SMALL SIGNAL DIODE SOT23 PACKAGE
D10 IMN10 ROHM 3 DIODE ARRAY - IMD PACKAGE
D11 BAT43W SCHOTTKY DIODE SOD123 PACKAGE (ALTERNATIVE BAT42W)
L1 NLC565050T-3R9K TDK 3.9uH SM INDUCTOR
L2 NLC565050T-3R9K TDK 3.9uH SM INDUCTOR
DISPLAY LE3228B-DNG-6190 DENSITRON 128 X 64 GRAPHIC DISPLAY

20-004-172
PRINTER STP411B-320 SEIKO THERMAL PRINTER MECHANISM
J1 MDS4 4 WAY MINI DIN SOCKET
J2 95001-2661 MOLEX 6 WAY DATA SOCKET
J3
J4
J5 DCP-20-PBT 2mm DC POWER SOCKET FROM G.ENGLISH ELECTRONICS
SPKR PKM35-4A0 MURATA PIEZO CERAMIC SOUNDER
X1 221-570 (F) 4.9152 MHz CRYSTAL CAN STYLE HC49/4H
X2 103-868 (F) 32.768 KHz WATCH CRYSTAL
X3 573-589 (F) 4 MHz CERAMIC RESONATOR
BAT 045-14 CR2450 3V LITHIUM 500mA­BAT1 050-14 7.2 VOLT 600mA-Hr NI CAD BATTERY PACK

20 WAY RIGHT ANGLED PIN HEADER
11 WAY RIGHT ANGLED PIN HEADER

12

Technical Support

Great Britain and World Headquarters

Micro Medical Ltd
PO Box 6
Rochester
Kent ME1 2AZ

Telephone + 44 (0)1634 360044
Fax [phone]
Web Site http://www.micromedical.com.uk
Email [e-mail]

Contact Micro Medical Ltd for the local agent in your region or country for local service:

13

Fault Analysis

The following analysis is only a guideline and should be carried out in a logical sequence. If the fault is
still apparent after the following suggestions then the unit should be fault found using the circuit
descriptions and circuit diagrams provided.

When the unit is turned on there is no display present

-Rotate contrast thumb wheel anti-clockwise to see if screen darkens.

-Connect charger to see if screen darkens and charging light illuminates.

When the unit is turned on the display is dark purple

-Rotate contrast thumb wheel clockwise to see if screen colour becomes lighter and characters are
displayed.

-Connect charger to see if screen characters appear.

FVC readings are low

-Remove Turbine from Transducer housing. Taking the Turbine, move it uniformly through the air and
check that the vane is not sticking.

The unit does not record any blows

-Inspect Transducer housing connector for damage.

-Check that Transducer housing lead is properly connected to J2.

-Remove Turbine from Transducer housing. Taking the Turbine, move it uniformly through the air and
check that the vane is not sticking.

-Blow into Transducer housing and move Transducer head cable around to check for breaks in the
cable.

14

15

16