GREER Company MicroGuard 400 Manual

Greer CompanyCrane Systems
GREER COMPANY 1918 E. Glenwood Place, Santa Ana, CA 92705 Tel: [phone] Fax: [phone]
MG®400 Computer Training Manual PN W424900 - 11/07/02
1 of 18
MicroGuard400 Service Training
Troubleshooting & Maintenance
TEST
100%
VIEW SET
INFORMATION
W
DOWNCLEAR UP SELECT
DEDUCT
ERECTED STOWED
OPERATOR ALARMS CONTRAST
WORKING
AREA
W
MAX
MicroGuard 424
5.82
3.46 ATB ALARM
60%
57.2 8F49.1
OUTRIGGERS 360o
MAIN BOOM
NO FLY OR JIB
CRANE
SET UP STOWED DEDUCT
RCI 414/424 Display
RCI 434 Display
MG®400 Computer Assembly
RCI 500 Display

Greer CompanyCrane Systems
GREER COMPANY 1918 E. Glenwood Place, Santa Ana, CA 92705 Tel: [phone] Fax: [phone]
MG®400 Computer Training Manual PN W424900 - 11/07/02
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MicroGuard®400 Service Training Manual
Table of Contents
General Description .........................................................................................................3
Fault Codes .....................................................................................................................4
Voltage Supplies and Checkpoints ..................................................................................5
Internal Power Supplies..............................................................................................5
Terminal Block Markings ............................................................................................6
Testing Pressure Transducers Through Drive Voltage ....................................................7
Pressure Transducer Resistance Measurement ........................................................8
Analog Input Terminals (AIN)...........................................................................................8
Extension “Pot” Operation................................................................................................9
Boom Extension Sensor (AIN2) .....................................................................................10
Boom Angle Sensor (AIN3)............................................................................................11
Extension Reel Assembly (reeling drum) .......................................................................12
Anti Two-Block System Components.............................................................................13
Where Do Relays Come From?...............................................................................14
Swing Potentiometer (Swing Pot) ..................................................................................15
Checking the Swing Potentiometer ..........................................................................16

Greer CompanyCrane Systems
GREER COMPANY 1918 E. Glenwood Place, Santa Ana, CA 92705 Tel: [phone] Fax: [phone]
MG®400 Computer Training Manual PN W424900 - 11/07/02
3 of 18
MicroGuard400 Computer
Troubleshooting & Maintenance
Overview
The MG® 400 Computer can be used with several different Greer RCI displays, most commonly
the RCI 500. Prior to 1999, several OEM’s used the MG® 400 as a “production line” computer.
In 1999, Greer introduced the MG® 500 Computer and the “Fast Cal” methods that equipment
manufacturers now employ.
General Description
The MG® 400 Computer is larger than the MG® 500 Computer. It contains two separate boards
called the processor board and the interface board.
The processor board on top contains all of the computer programming, stores the memory, does
the calculating, and supplies the visual outputs for the RCI display. The interface board below
contains two voltage power supplies that provide the voltages necessary for operation of the
computer and the display, including the analog and digital functions. The interface board routes
these voltages to the appropriate locations.
The larger power supply source with the light is responsible for 5 volt power; the smaller power
supply produces the 15 volts used in conjunction with several different power applications.
There are numerous “voltage check points” on both the processor and the interface boards,
as well as electrical checks involving the interface board terminal blocks, e.g., drive voltage for
the analog sensor functions.
Improper handling of the computer unit may cause damage to the upper board as the cover and
boards are not hinged. For handling instructions, refer to the Greer maintenance manual.
Fault Codes
When a fault is detected by the system, a number will appear under one or more of the four fault
group headings (A - D) shown on the next page. The information screen will illuminate the word
“FAULT,” the RED LED will light up, and the audible alarm will sound.
To diagnose Faults in the system at any time during operation, PRESS and HOLD the “TEST”
button, which will initiate the self-test function followed by an on-screen display of identied faults
in groups A through D.

Greer CompanyCrane Systems
GREER COMPANY 1918 E. Glenwood Place, Santa Ana, CA 92705 Tel: [phone] Fax: [phone]
MG®400 Computer Training Manual PN W424900 - 11/07/02
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Fault Codes continued
Group “A”
Sensor Faults
Group “B”
I/O Faults
Group “C”
Memory Faults
Group “D”
General Faults
001 Piston Pressure 00 No Fault 00 No Fault 00 No Fault
002 Rod Pressure 01 Digital input/output 01 Executive Rom 01 No Duty Found
004 Boom Extension 02 Analog input/output 02 Duty Rom 02 Current Duty Bad
008 Boom Angle 04 Display 03 Not Used 04 Configuration
Uncalibrated
016 Not Used 04 Scratchpad Rom
032 Swing “A” 08 Personality Rom
064 Swing “B”
Faults in the external sensors are detected without the need of the self-test .
The above faults do not include the entire list of possible Faults and Fault Codes. Please see the
maintenance manual for a complete listing.
Interpreting Multiple Faults that Add Up to More than the Numbers Listed.
Example: If the fault is 012, pick the largest fault(s) from the list that will subtract from 12 and
then add to get the equivalent. In this instance, the answer would be 008 and 004.
In this example, the faults indicate that both the extension and angle sensor have failed. Fault
indications of this type are unlikely, however, there should be an investigation of electrical
readings and cable routings. Outputs from analog sensors can be measured with an accurate
voltmeter.

Greer CompanyCrane Systems
GREER COMPANY 1918 E. Glenwood Place, Santa Ana, CA 92705 Tel: [phone] Fax: [phone]
MG®400 Computer Training Manual PN W424900 - 11/07/02
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Checkpoint Requirement Tolerance
B+ +9-36V .5
+VP +12V -.5
+5 +5 +/- .1
+15 +15 +/- .1
-15 -15 +/- .1
Voltage Supplies and Check Points
Look at the terminal board and begin supplying power to it.
The main power coming into the terminal board is usually a
9-36 VDC supply coming directly from the crane. If the
voltages at the B + and B - terminals on TB -1 are not
present, check the voltage on the vehicle.
Internal Power Supplies: The computer generates its
own internal power from the incoming battery voltage. This
power can be monitored at the test points inside the
computer adjacent to the fuses and Battery Input
Terminals. The tolerances for these voltages are listed in
the table below as well as in a graphic illustrating the
voltage check points.
To monitor the internal power supplies, use a digital voltmeter set to the appropriate VDC setting
and attach to the appropriate voltage check points on the terminal board. Note the two power
supplies sitting side-by-side on the board. The larger (left) power supply provides 5 V power.
The smaller (right) power supply provides 15 V. There are two fuses on the face of the board
immediately above the voltage checkpoints. These 1A fuses, labeled “FS1” and “FS2,” protect
the functions of display power and power supply. Replace these fuses ONLY with an identical
replacement, or damage may occur to the main board or tracings.
5 V
15V
FS1
FS2
B+
GND
+VP
+5V
Res
+15V
-15V

Greer CompanyCrane Systems
GREER COMPANY 1918 E. Glenwood Place, Santa Ana, CA 92705 Tel: [phone] Fax: [phone]
MG®400 Computer Training Manual PN W424900 - 11/07/02
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Terminal Block Markings
Terminal blocks are marked as shown in the graphic to
the right. Note that there are multiple Drive Voltage
terminals (DR+ and DR-) in different locations. Note that
these terminals are all common on the computer board
assembly. The same is true of any OV or +VP terminals.
For example, checking the drive voltage on TB2 should
provide exactly the same readout as at any drive voltage
terminal on TB3.
AIN2 and AIN3 are typical voltages checkpoints for
analog input signals from the boom angle and length
pots. These signals will vary depending on how the unit
is operated at the time the reading is taken. Refer to the
maintenance manual for further definition of terminal
blocks.
Because the drive voltages are all common, any analog
sensor can be suspect. If, for example, drive voltage is
low, and +15 V is within tolerance, each of the analog
sensors must be removed, one at a time, until the sensor
that is causing the voltage to sag is located and replaced. If the voltage continues to sag, the
processor board should be replaced as the drive voltage power supply is integrated into the
processor board.
This is a simple process of elimination, which will help pinpoint a failing sensor, an abrasion, or a
pinch in a wire or loom. All wiring could become suspect at this time and should be carefully
checked. Output tests can also be run at the sensors by attaching the voltage meter at the
sensor output and watching as the sensor is extended or raised. Voltage skips or gaps can be
detected using this technique.
+DR
0V
-DR
+DR
0V
+DR
-DR
-DR
0V
AIN1
AIN0
-DR
AIN5
AIN6
AIN2
+VP
0V
+DR
+DR
TX0-
TX0+ AIN4
TX1+
TX1-
-DR
0V
AIN3
+VP
+VP
OV
OV
OV
OV
OV
TB2
TB3
TB4
Voltage Checks

Greer CompanyCrane Systems
GREER COMPANY 1918 E. Glenwood Place, Santa Ana, CA 92705 Tel: [phone] Fax: [phone]
MG®400 Computer Training Manual PN W424900 - 11/07/02
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Testing Pressure Transducers Through Drive Voltage
The pressure transducer used with the MG® 400 Computer is a remote pressure transducer. It
is usually mounted directly onto the boom lift cylinder and cabled into the computer through
connectors that are attached to the proper drive and output channels. The transducer starts out
as a balanced bridge with Drive Voltage input, and “0” output. As soon as the boom is raised,
which applies moment to the cylinder, the internal pressure will change in the transducer and the
resistance across the bridge will change, causing output to the TX0, TX1 side of the bridge.
This output indicates to the computer that the weight or center of gravity of the boom is
changing. The reading is then converted to load.
To check the input and outputs on this circuit, go to the terminal blocks marked DR+ and DR-,
and TX0+ and TX0-. The terminal located immediately below the base-side transducer is the
rod-side transducer. In the maintenance manual, there is a procedure for the changeout and
setup of a new transducer. Refer to the Greer Calibration manual for the procedures for zeroing
the transducer and performing load tests.
Refer to the procedure on the following page for testing the resistance of a normal transducer.
Remember that the readings must balance. If not, the transducer is unbalanced and may give
faulty load readings.
DR+
DR-
TX0+
TX0-
DR+
DR-
TX0-TX1

Greer CompanyCrane Systems
GREER COMPANY 1918 E. Glenwood Place, Santa Ana, CA 92705 Tel: [phone] Fax: [phone]
MG®400 Computer Training Manual PN W424900 - 11/07/02
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Pressure Transducer Resistance Measurement
• With the power to the computer off, disconnect the piston pressure transducer from the
terminal blocks +DR, -DR, TX0+ and TX0- within the computer.
• With the DVM set to the Ohms range, measure the resistance between red and blue wires.
The resistance should be 350 Ω+/- 10 Ω.
• With the DVM set to the Ohms range, measure the resistance between yellow and green
wires. The resistance should be 350 Ω+/- 10 Ω.
• With the DVM set to the Ohms range, measure the resistance between pins. Each of the
open wires red, blue, green, yellow and the case of the transducer. There should be no
connection between the case and any of the pins.
Analog Input Terminals (AIN)
Some terminals on terminal strip TB3 will be marked “AIN” followed by a numeral
(0, 1, 2, etc.) “AIN” stands for Analog Input. This means that at this terminal there is an
incoming signal to the computer from an analog sensor, such as extension, or boom
angle. It is important to be able to identify which terminal goes to which function, as a
voltage reading may be necessary to determine if a problem with one of the analog
sensors exists. Therefore, each of the “AIN” channels must be identified as well as what
information each one feeds into the computer. The first Analog sensor identified here
will be the extension sensor.
Red
Blue
Green
Yellow
Typical Transducer W/ Wiring

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GREER COMPANY 1918 E. Glenwood Place, Santa Ana, CA 92705 Tel: [phone] Fax: [phone]
MG®400 Computer Training Manual PN W424900 - 11/07/02
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Approx. .25 Volts
Retracted
Approx. 2.5 Volts Extended
+-
OUTPUT
+-
OUTPUT
Extension Pot Operation
As discussed in earlier lessons, the extension
pot is a precision 10-turn pot. Drive voltage is
introduced into the + side, and - to the other
end of the coil.
The output side or “wiper,” as it is sometimes
called, will have a set starting point
(normally .25 V) and as the pot is rotated, the
voltage will linearly increase until at some point,
it will reach the drive voltage, which is 5.25 V
(+- .25 V).
This voltage rise must be steady and consistent
without voltage spikes or skips where the
voltage drops off. Using a voltmeter, measure
the reading at “AIN2” on the computer
termination board. The schematic below illustrates checkpoints, followed by an explanation of
the checkout procedure on the next page.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
+DR
AIN0
AIN1
-DR
OV
+DR
AIN2
AIN3
AIN4
-DR
0V
+DR
AIN5
AIN6
-DR
0V
TB3
Approximate Voltages
For Training Purposes
Only
0 Volts
5 Volts
Retracted
Extended
0 Volts
Retracted
Extended
Output
Extension Pot Schematic

Greer CompanyCrane Systems
GREER COMPANY 1918 E. Glenwood Place, Santa Ana, CA 92705 Tel: [phone] Fax: [phone]
MG®400 Computer Training Manual PN W424900 - 11/07/02
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Boom Extension Sensor Ain2
To check the Boom Extension Sensor Voltage, follow the procedure below. To access the
voltage checkpoints, carefully remove the computer cover. Move the processor board out of the
way and secure it to prevent damage. Remove the extension reel cover for access to the
terminal strip in the computer reel.
1. Fully retract the boom. Access the computer and termination boards. Using a digital
voltmeter set to read DC voltage, measure the analog sensor drive voltage. Place the
negative lead on any 0 (Zero) volt or DR- terminal of the Analog Input Group.
2. Place the positive lead of the meter on the AIN2 terminal of the Analog Input Group. The
voltage should be greater than 0.25 volts.
3. Extend the boom as far as is safe to do so. The boom need not be horizontal for this test.
The voltage should be less than 5 volts. (Usually around 2.5 volts depending on the boom
length). During extension, the voltage should increase linearly; during retraction the
voltage should decrease linearly.
4. If the voltage is out of the range listed above, remove the four screws that secure the cover
on the extension reel, which is located on the left side of the main boom section; remove the
cover.
5. Under the cover on the right side of the extension reel is a terminal strip. This terminal strip
has six wires connected to the bottom screws. With a digital voltmeter set to read DC
voltage, place the negative lead on the terminal with the attached blue wire (- Drive) and the
positive lead on the terminal with the attached red wire (+Drive).
6. The voltage should be 5.25+/-0.1 volts. If this voltage is out of range, and if the Analog Drive
Voltage measured in the computer was OK, it is possible that the cable is open or grounded
between the computer and the extension reel. Check all connections and plugs that may be
between these two components. Repair or replace as required. Refer to the proper wiring
schematic for the unit being worked on. For wiring details, refer to the Installation Manual for
the model of the crane being tested or OEM wiring schematics.
7. With the negative lead of the voltmeter connected to the blue drive (negative) and the
positive lead of the voltmeter connected to white (extension signal), the voltage should be
the same as the voltage measured at AIN2 of the analog input group in the computer. If this
voltage is not the same, it is possible that the cable between the reel and the computer is
faulty.