Apollo

Model SL40 VHF COMM Transceiver

Field Maintenance Manual

PRELIMINARY

April, 1997 Draft 3 560-1014-00

 1997 by II Morrow Inc. All rights reserved.
Printed in the USA

No part of this document may be transmitted, reproduced, or copied in any form or by any means
without the prior written consent of II Morrow Inc. Due to II Morrow’s commitment to
constantly improve the quality and performance of our products, information contained in this
document is subject to change without notice.

II Morrow and Apollo are registered trademarks of II Morrow Inc.

II Morrow Inc. 2345 Turner Rd. SE

PO Box 13549 Salem, OR 97302
Salem, OR 97309 USA

Phone (503)581-8101
1-800-525-6726
In Canada 1-800-654-3415
FAX (503)364-2138
HISTORY OF REVISIONS
Revision Date Description
-- 4/8/97 Draft 3.

ORDERING INFORMATION
To receive additional copies of this publication, order part # 560-1014, Apollo SL40 VHF
COMM Transceiver Field Maintenance Manual.

REFERENCE PUBLICATIONS
Following are other publications referenced in this guide.

IPC 610A Acceptability of Electronic Assemblies

560-0956 Apollo Model SL40 VHF COMM Transceiver Installation Manual
NOTES
 Table of Contents

TABLE OF CONTENTS
SECTION 1 - INTRODUCTION................................................................................................. 1
ABOUT THIS MANUAL ...................................................................................................................... 1
APOLLO SL40 DESCRIPTION ............................................................................................................. 1
FEATURES ......................................................................................................................................... 1
REGULATORY COMPLIANCE ............................................................................................................. 2
HANDLING CONSIDERATIONS ........................................................................................................... 2
ESD PROTECTION ..................................................................................................................................................... 2
COMPONENT HANDLING............................................................................................................................................ 3
SHIPPING CONSIDERATIONS....................................................................................................................................... 3
OTHER TOOLS AND EQUIPMENT ....................................................................................................... 3
TOOLS ....................................................................................................................................................................... 3
TEST EQUIPMENT ...................................................................................................................................................... 3
SECTION 2 - TROUBLESHOOTING ....................................................................................... 5
OVERVIEW ........................................................................................................................................ 5
ESD SAFE WORK AREA REQUIREMENTS ......................................................................................... 5
PRELIMINARY CHECKOUT................................................................................................................. 5
SYSTEM FUNCTIONS ......................................................................................................................... 6
SOFTWARE VERSION DISPLAY................................................................................................................................... 6
SIGNAL STRENGTH DISPLAY...................................................................................................................................... 6
AUDIO NOISE LEVEL DISPLAY................................................................................................................................... 6
HEADPHONE LEVEL DISPLAY AND ADJUSTMENT ...................................................................................................... 7
INTERCOM SQUELCH THRESHOLD DISPLAY AND ADJUSTMENT................................................................................. 7
INTERCOM AUDIO LEVEL DISPLAY AND ADJUSTMENT .............................................................................................. 7
SIDETONE LEVEL DISPLAY AND ADJUSTMENT .......................................................................................................... 7
BASE STATION LOCKOUT MODE DISPLAY AND ADJUSTMENT ................................................................................... 8
TEST MODE OPERATION ................................................................................................................... 9
TEST MODE ACCESS ................................................................................................................................................. 9
GENERAL OPERATION ............................................................................................................................................... 9
TEST MODE PAGE ..................................................................................................................................................... 9
DISPLAY TEST FUNCTION .......................................................................................................................................... 9
CONTROLS TEST FUNCTION .................................................................................................................................... 10
TEST SETUP .................................................................................................................................... 10
EQUIPMENT TESTS .......................................................................................................................... 12
TRANSMITTER ........................................................................................................................... 13
TRANSMITTER PERFORMANCE ................................................................................................................................ 13
TRANSMITTER FREQUENCY ERROR ......................................................................................................................... 13
TRANSMITTER POWER MEASUREMENT ................................................................................................................... 14
TRANSMITTER MODULATION ................................................................................................................................... 15
TRANSMITTER SNR (SIGNAL TO NOISE RATIO) ........................................................................................................ 16
TRANSMITTER AUDIO DISTORTION........................................................................................................................... 17
RECEIVER.................................................................................................................................... 17
RECEIVER PERFORMANCE ....................................................................................................................................... 18
SPEAKER AUDIO TEST...................................................................................................................................... 18
RECEIVER SENSITIVITY ................................................................................................................................... 19
UNIT DISASSEMBLY / REASSEMBLY ................................................................................................ 20
DISASSEMBLY ......................................................................................................................................................... 20
REASSEMBLY .......................................................................................................................................................... 21

Apollo SL40 Field Maintenance Manual i

Table of Contents

REPLACEABLE COMPONENTS ......................................................................................................... 22

COMPONENT LISTING............................................................................................................................................... 22
REPLACEMENT POLICY ............................................................................................................................................ 22
PACKAGING FOR SHIPMENT ..................................................................................................................................... 22
CONTACTING THE FACTORY FOR ASSISTANCE................................................................................ 22
SECTION 3 - CHECKOUT PROCEDURES .......................................................................... 25
GENERAL ....................................................................................................................................... 25
SERVICE VERIFICATION .................................................................................................................. 25
FUNCTIONAL CHECKOUT ................................................................................................................ 25
DISPLAY CHECK ...................................................................................................................................................... 25
CONTROLS TEST ...................................................................................................................................................... 25
TRANSMITTER TESTS ............................................................................................................................................... 25
RECEIVER TESTS ..................................................................................................................................................... 25
APPENDIX A - TEST DATA LOG .......................................................................................... 27
POST INSTALLATION CHECKOUT .................................................................................................... 27
SIDETONE LEVEL ADJUSTMENT ...................................................................................................... 27
FLIGHT TEST CHECK ...................................................................................................................... 27

LIST OF TABLES
TABLE 1 REPLACEABLE COMPONENTS .......................................................................................... 22

LIST OF ILLUSTRATIONS
FIGURE 1 SL40 FRONT PANEL ........................................................................................................ 2
FIGURE 2. TEST SETUP DIAGRAM ................................................................................................... 11
FIGURE 3. EQUIPMENT CONNECTION.............................................................................................. 11
FIGURE 4. TRANSMITTER TEST SETUP ............................................................................................ 14
FIGURE 5. RECEIVER TEST SETUP .................................................................................................. 19
FIGURE 6. COM MAIN BOARD OUTLINE ......................................................................................... 20

ii Apollo SL40 Field Maintenance Manual

 Introduction

SECTION 1 - INTRODUCTION
ABOUT THIS MANUAL
This manual provides performance checkout instructions, troubleshooting instructions to the
board level, disassembly and reassembly procedures, and test procedures to verify that the unit
is once again operational. It is intended for use by persons certified by the Federal Aviation
Administration (FAA) to repair aircraft communication devices.

Section 1 Provides an introduction to the SL40 unit, details handling and shipping
considerations for the components, and lists required tools and test equipment.
Section 2 Includes all troubleshooting procedures, test setups, disassembly/reassembly, and
identifies replaceable components.
Section 3 Includes checkout procedures to ensure that repairs have been properly
completed and unit is fully serviceable
Appendix A Includes post repair test data log sheets.

APOLLO SL40 DESCRIPTION

The Apollo SL40 is a 760 channel VHF Comm transceiver. It is one member of the Apollo
slimline series which includes the SL40 Comm, the SL50 GPS, and the SL60 GPS/Comm.

FEATURES
The features of the SL40 Comm include:
• 760 channels
• Frequency range of 118.000 to 136.975 MHz
• Active and standby frequency display
• 16 character high-intensity alphanumeric LED display
• Automatic display intensity
• Back-lit buttons
• Transmit status indicator
• Frequency memory and recall functions
− from remote source
− eight last used
− eight user stored
• Weather channels
• Frequency monitor function
• Built-in intercom function
• Stuck mic time-out
• Two microphone inputs
• Internal non-volatile memory - no battery required
• Full range input supply voltage
• 12 watt audio amplifier

Apollo SL40 Field Maintenance Manual 1

Introduction

Figure 1 SL40 Front Panel

REGULATORY COMPLIANCE
The Apollo SL40 is designed and tested to meet the following TSOs:
FAA TSO-C37d for transmit
FAA TSO-C38d for receive
FAA TSO-C128 for unintentional transmission (stuck mic)
The Apollo SL40 complies with the FCC requirements specified in:
CFR 47, Part 87, Aviation Services, Subpart D, Technical Requirements
CFR 47, Part 15, Radio Frequency Devices, Subpart B, Unintentional Radiators
The Apollo SL40 software is designed and tested to RTCA/DO-178B, level C.
Note: Unauthorized changes or modifications to the SL40 may void the compliance to
required regulatory agencies and authorization for continued equipment usage.

HANDLING CONSIDERATIONS

ESD PROTECTION
The case on the SL40 is designed to protect the components from mechanical damage and
also provides protection from damage due to electrostatic discharge. Open the case only
when the unit is in an ESD safe work area. Observe proper ESD techniques when
working on the unit.

2 Apollo SL40 Field Maintenance Manual

 Introduction

COMPONENT HANDLING
The SL40 contains electrostatic discharge sensitive (ESDS) components. Care must be
taken when handling these devices to prevent damage. Special precautions for ESD work
areas are detailed in ESD Safe Work Area Requirements, Page 5. Both you and the work
surface must be properly grounded before handling the SL40 components. If moving the
SL40 components from one area to another, they must either be reinstalled in the SL40
case or placed in an anti-static bag.

SHIPPING CONSIDERATIONS
All SL40 components must be returned to the factory in anti-static packaging equivalent
to that used to ship the components from the factory. Save the packaging from the
replacement components to use when returning the failed component. Packaging
instructions are provided on Page 22. If you have questions regarding shipment of the
SL40 components, contact the II Morrow Service Department. Information on how to
contact the factory is provided on Page 22.

OTHER TOOLS AND EQUIPMENT

The following tools and test equipment (or equivalent) are required to properly evaluate
and test the SL40. All test equipment must be calibrated before performing the test
procedures in this manual.

TOOLS
A 3/32” hex tool is required to remove the SL40 from the mounting frame in the aircraft.
A #2 Phillips screwdriver is required for disassembly

TEST EQUIPMENT
a. Power Supply:
HP6433B DC Power Supply (0-36 V 0-10A) or equivalent
b. RF Signal Generator:
HP8920 RF Communications Test Set or equivalent
c. Multimeter
FLUKE 8010A Digital Multimeter or equivalent
d. Test interface
Refer to Figure 2 for the Test Interface schematic and SL 40 transceiver setup.

Apollo SL40 Field Maintenance Manual 3

Introduction

NOTES

4 Apollo SL40 Field Maintenance Manual

 Troubleshooting

SECTION 2 - TROUBLESHOOTING
This section provides information to assist in isolating problems with the SL40. Where
required, detailed drawings of test setups are provided. The specified test equipment is a
recommendation based on the equipment used to test the SL40 during manufacture and
factory service. Alternate, but equivalent, equipment may be substituted if the recommended
equipment is not available.

OVERVIEW
Field maintenance of the SL40 is limited to replacement of the SP96 Com Display Board
and the VHF Com Main board.

ESD SAFE WORK AREA REQUIREMENTS

The SL40 circuit boards contain electrostatic discharge sensitive (ESDS) components. To
prevent damage to the ESDS components, the circuit boards must be removed from the
SL40 and handled in an ESD safe work area only. The work area must comply with the
requirements of IPC 610A or other equivalent document. At a minimum, observe the
following the following precautions when handling SL40 components.
Both you and the work surface must be properly grounded before handling the SL40
components. If moving the SL40 components from one area to another, they must either
be reinstalled in the SL40 case or placed in an anti-static bag.

PRELIMINARY CHECKOUT
Perform the following tests before removing the SL40 from the aircraft to determine if
the problem is in the SL40 or the aircraft.
Transmission and reception range is normally not a problem in aircraft due to the aircraft
height above terrain. Poor reception range that can be traced to aircraft noise or antenna
performance is usually repairable.
The SL40 has a number of “System Functions” to assist in isolating Comm problems.
Two of these features assist the operator or service personnel, in evaluating the aircraft
communication environment: Signal Strength Display (RFLVL) and Audio Noise Level
Display (NOISE). Additionally, there are several adjustments, which if improperly set,
can give the appearance of a malfunctioning radio. If the system functions fail to pinpoint
or correct a Comm problem remove the SL40 from the aircraft and refer to the Equipment
Test procedures on Page 12 for bench testing. A built in Display test function allows
isolation of Com Display board malfunctions with the SL40 mounted in the aircraft. If a
problem is isolated to the SL40 (Com Display board or Com Main board) refer to the
Disassembly procedures on Page 20 for instructions on removing and replacing the
malfunctioning component.

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Troubleshooting

SYSTEM FUNCTIONS
The following functions are available in the normal operating mode to assist in isolating
problems:
• software version display
• signal strength display
• audio noise level display
• headphone level display and adjustment
• intercom squelch threshold display and adjustment
• intercom audio level display and adjustment
• sidetone audio level display and adjustment
• base station lockout mode display and adjustment
The system functions are enabled by pressing the MON button for three seconds. The LED
above the MON button will turn off. Rotate the LARGE knob to select the function. The
software version page will be the initial display.
The front panel buttons will operate normally during display of the system functions.
Pressing any button will revert back to the normal mode defined for the button. The
receiver will also operate normally during display of the system functions.

SOFTWARE VERSION DISPLAY

This function displays the COM software version.
SW VER 1.0

SIGNAL STRENGTH DISPLAY

This function is used to display the signal strength of received signals.
RFLVL 087
With a dummy antenna connected, this function will normally be in the range 13 to 16.
Full transceiver functions are operational during this function, including transmit.

Note: The rf signal strength is an 8-bit value with a range of 0 to 255

from the IF/RF agc voltage as read into the µcontroller through an
A/D input.

AUDIO NOISE LEVEL DISPLAY

This function is used to display the noise level of the received audio.
NOISE 005
With a dummy antenna connected, this function will normally be in the range 162 to 170.
Full transceiver functions are operational during this function, including transmit.

6 Apollo SL40 Field Maintenance Manual

 Troubleshooting

Note: The noise level is an 8-bit value with a range of 0 to 255 from the
noise level detector as read into the µcontroller through an A/D
input.

HEADPHONE LEVEL DISPLAY AND ADJUSTMENT

This function is used to display and adjust the headphone audio level. Turning the small
knob changes the value. Setting the value to 0 slaves the headphone audio level to the
volume control knob. Setting to a non-zero value gives a fixed headphone audio level.
HphLv 000

Full transceiver functions are operational during this function, including transmit.

Note: The headphone level is an 8-bit value with a range of 0 to 255.

INTERCOM SQUELCH THRESHOLD DISPLAY AND ADJUSTMENT

This function is used to display and adjust the intercom squelch threshold level. Turning
the small knob changes the threshold.
IcmSq 200

Full transceiver functions are operational during this function, including transmit.

Note: The intercom squelch threshold level is an 8-bit value with a range
of 0 to 255.

INTERCOM AUDIO LEVEL DISPLAY AND ADJUSTMENT

This function is used to display and adjust the intercom audio level. Turning the small
knob changes the value. Setting the value to 0 slaves the intercom level to the volume
control knob. Setting to a non-zero value gives a fixed intercom audio level.
IcmLv 000

Full transceiver functions are operational during this function, including transmit.

Note: The intercom level is an 8-bit value with a range of 0 to 255.

SIDETONE LEVEL DISPLAY AND ADJUSTMENT

This function is used to display and adjust the sidetone audio level. Turning the small
knob changes the value. Setting the value to 0 slaves the sidetone audio level to the
volume control knob. Setting to a non-zero value gives a fixed sidetone audio level.
SidLv 000

Apollo SL40 Field Maintenance Manual 7

Troubleshooting

Full transceiver functions are operational during this function, including transmit.

Note: The sidetone level is an 8-bit value with a range of 0 to 255.

BASE STATION LOCKOUT MODE DISPLAY AND ADJUSTMENT

This function is used to display and adjust the lockout mode. Improperly set, the lockout can
disable various Comm functions giving the appearance of a malfunctioning unit. Turning the
small knob changes the mode. The modes are summarized as follows.

Locks 000

• Mode 0: Normal pilot mode. No disabled functions

• Mode 1 & 3: Toggle Lock. Only the Flip-Flop button is disabled.

Fixed Primary frequency.
Variable Standby frequency.
Frequencies cannot be swapped.

• Mode 2 & 6: Primary Frequency Protected.

Fixed Primary frequency.
Variable Standby frequency.
Frequencies can be swapped.
Primary is not modifiable when it is the standby freq.
(displayed as Mode 6)

• Mode 4: Fixed Two Channel radio.

Both frequencies are fixed.
Frequencies CAN be swapped.

• Mode 5 & 7: Toggle Lock w/ fixed standby frequency.

Both frequencies are fixed.
Frequencies CANNOT be swapped.

Note that it is possible to put the unit into mode 8, but on re-entry to the system functions, it
will be show as mode 0.

Full transceiver functions are operational during this function, including transmit.

Note: The lockout mode has a range of 000 to 008.

While viewing the frequency display, use the large and small knobs on the right side of
the SL40 to select an unused local channel. Toggle this frequency to the active channel.
Press and hold the MON button for about 3 seconds to reach the System Function. Use

8 Apollo SL40 Field Maintenance Manual

 Troubleshooting

the large knob to select the NOISE function and view the receive noise level of the
selected frequency. The value will change constantly, and has a range between 0 and 255
and an RFLVL in the mid teens (14 to 17). On the service bench with the antenna port of
the SL40 dummy loaded, NOISE should be between 100 and 125. If the SL40 is
connected to the aircraft antenna and there is no carrier on the channel, expect the reading
to be the same or slightly lower. To confirm that there is no carrier on the monitored
channel pull the squelch knob and listen.

TEST MODE OPERATION

The test mode allows the SL40 display and controls to be tested with the unit still
mounted in the aircraft. The test mode is also used to access certain test and calibration
functions used during manufacture and at the service center. Do not change or adjust any
functions accessed in the test mode unless specific instructions are provided in this
manual. If the SL40 fails either the Display or Controls test, remove the unit from the
aircraft and refer to the Disassembly procedures on Page 20 for instructions on removing
the Com Display board.

TEST MODE ACCESS

Enable the built-in test mode by pressing the ⇔ (flip/flop) and RCL buttons while
switching the unit on.

GENERAL OPERATION
In test mode operation, the LARGE knob is used to select the different test functions, the
SMALL knob is used to select additional pages for each test function. In general, the only
test functions that will be used at the Field Maintenance level are the Display test and the
Controls test. Do not modify any setting displayed while in the test mode.

TEST MODE PAGE

The “Test Mode Page” is the first page displayed in the test mode
TEST MODE

When this page is displayed, pressing the MEM button will return the COM to normal
mode operation.

DISPLAY TEST FUNCTION

This function is used to test the display and LED indicators.
DISPLAY TEST

Press the MEM button to execute the display test. The display will sequence through the
test by turning on the first four characters, the 2nd four, the 3rd four, and then the last
four characters. Once the sequence is complete, “DISPLAY TEST” will be displayed.

Apollo SL40 Field Maintenance Manual 9

Troubleshooting

Note: This function will not turn on all 35 dots on all 16 characters at
the same time. This would cause excessive current.

CONTROLS TEST FUNCTION

The controls test function is used to test the control inputs from the front panel.
As each button is pressed, the display indicates the button and the LED is turned on over
the corresponding button. SQ displays when the squelch knob is pulled out.
CONTROLS <->
TX ⇔ button pressed
CONTROLS SQ <->
TX ⇔ button pressed and squelch knob pulled out

CONTROLS EC
“EC” button pressed

CONTROLS MON
“MON” button pressed

CONTROLS RCL
“RCL” button pressed

CONTROLS MEM
“MEM” button pressed

When the SMALL knob is turned, the magnitude is displayed (000 to 255). All LEDs are
turned off.
CONTROLS 045
The LARGE knob is not tested in this function. It is tested by default by selecting the
various test functions.

TEST SETUP
A schematic of the SL40 transceiver test setup is shown in Figure 2. Figure 3 is a graphic
presentation of the recommended equipment connected for test.

10 Apollo SL40 Field Maintenance Manual

 Troubleshooting

Figure 2. Test Setup Diagram

Figure 3. Equipment Connection

Apollo SL40 Field Maintenance Manual 11

Troubleshooting

EQUIPMENT TESTS
The tests in the following paragraphs will isolate an SL40 problem to the Com Main
board level. If the unit fails any of the tests in either the Transmitter or Receiver sections,
refer to the Disassembly/Reassembly procedures on Page 22 for instructions on removing
the faulty component. The operating specifications listed below are effective for all
equipment tests.
Input voltage 10 Vdc to 40 Vdc, reverse polarity protected
Input current 300 mA typical, 2 A maximum at 13.75 V dc, receive 140
mA typical, 900 mA at 27.5 Vdc, receive 2.1 A typical, 3.2
A maximum at 13.75 Vdc, transmit 1.0 A typical, 1.4 A
maximum at 27.5 Vdc, transmit
NOTE: Receiver maximum at full receive audio, transmit maximum at
90% modulation at 1000Hz.
Input power 4 watts typical, receive 28 watts typical transmit.
Internal fuse 7 amp fast blow, solder on board.
Antenna requirements Standard 50Ω vertically polarized with VSWR <2.5:1.
a) There are no adjustments for the SL40.

b) These test procedures should be performed with the SL40 on the service bench to
isolate suspected service failures. The same tests can be used after replacement of
subassemblies to verify proper operation prior to returning the SL40 to service,.

c) The HP 8920 AM software (HP 11807A) will automatically test the SL 40. The
specifications are listed in the SL40 VHF COMM Transceiver Installation Manual.

d) Perform all tests at normal room temperature (68° to 72° F).

e) Complete the transmitter frequency test before performance evaluating the receiver.

NOTE: All RF voltages are "HARD" Micro volts. "Hard" micro volts
indicates use of a 6 dB pad between the signal generator and the
receiver. When using the HP 8920 “HARD” should be set in the
test equipment configuration MENU.

12 Apollo SL40 Field Maintenance Manual

 Troubleshooting

TRANSMITTER
TRANSMITTER PERFORMANCE
The following specifications define expected transmitter performance.
Class 4
Output Power 8 watts minimum carrier at 12 VDC input.
6 watts minimum carrier at 10 VDC input.
The transmit is lock out below 9 VDC input
Frequency range 118.000 to 136.975 MHz, 750 channels
Frequency tolerance ±15 PPM from 20°C to + 70°C
Microphone input Two inputs, standard carbon or dynamic MIC with
integrated preamp providing minimum 70 mV rms into
1000Ω load.
Modulation capability 85% with 100 mV to 1000 mV rms microphone input at
1000 Hz.
Audio frequency distortion <10% at 85% modulation at 350 to 2500 Hz.
Audio frequency response <4dB variation with 350 to 2500 Hz, 85% modulation.
Carrier noise >35dB down
Sidetone output up to 280 mW into 100Ω, 120 mW into 500Ω.
Duty cycle 100%
Stuck Mic time-out 35 seconds, reverts to receive.
Transmit key Input pull low to enable transmitter

TRANSMITTER FREQUENCY ERROR

Transmitter Frequency error is measured using the HP 8920. This is accomplished by
presetting the SL40 to the same channel as the HP8920 and reading the frequency error
from the HP8920 Communications Test Set.

NOTE: Set the DC supply voltage to 13.75 volts ± 0.75 volts prior to
performance evaluating the transmitter.

Procedure:
1. Set the HP 8920 as listed below. Use Figure 3 and Figure 4 as guides.
Press PRESET
Press TX function

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Troubleshooting

Figure 4. Transmitter Test Setup

2. Using the CURSOR control knob or the USER keys set:

AUTO MANUAL MANUAL
TUNE Freq 127.5 MHz See NOTE below
TX PWR 0
RF IN/ ANT RF IN
AF ANAL IN AM Demod
De-EMPHASIS off
Detector PK+-/2
AF GEN Freq. 1 kHz
AF GEN LVL off

NOTE: Where interference may be a problem, use any unused channel for both
the SL40 and the HP 8920 as long as both are on the same frequency.
A frequency close to center of operating range is preferred.

3. Set the SL40 as listed below.

While viewing the frequency display, use the Large and Small knobs on the right
side of the SL40 to select 127.5 MHz.
Toggle this frequency into the Active channel.
Press the PTT button on the test panel.
EXPECTED RESULTS TX Freq. Error 0 ± 15 PPM
4. UN-key the transmitter

TRANSMITTER POWER MEASUREMENT

Transmitter power is measured using the HP8920. This is accomplished by presetting the
SL40 to the same channel as the HP8920 and reading the transmitter power output, with
no MIC audio input.

14 Apollo SL40 Field Maintenance Manual

 Troubleshooting

NOTE: Set the DC supply voltage to 13.75 volts ± 0.75 volts prior to
performance evaluating the transmitter.

Procedure:
1. Set the HP 8920 as listed below. Use Figure 3 and Figure 4 as guides.
Press PRESET
Press TX function
Using the CURSOR control knob or the USER keys set:
AUTO MANUAL MANUAL
TUNE Freq 127.5 MHz See NOTE below
TX PWR 0
RF IN/ ANT RF IN
AF ANAL IN AM Demod
De-EMPHASIS off
Detector PK+-/2
AF GEN Freq 1 kHz
AF GEN LVL off

NOTE: Where interference may be a problem, use any unused channel for both
the SL40 and the HP 8920 as long as both are on the same frequency.
A frequency close to center of operating range is preferred.

2. Set the SL40 as listed below.

While viewing the frequency display, use the large and small knob on the right
side of the SL40 to select 127.5 MHz.
Toggle this frequency into the Active channel.
Press the PTT button on the test panel.

EXPECTED RESULTS: TX PWR > 8 watts

3. UN-key the transmitter

TRANSMITTER MODULATION
Transmitter modulation is measured using the HP8920. This is accomplished by
presetting the SL40 to the same channel as the HP8920; inputting a 1000 Hz tone at 50 to
100 mV at MIC 1 and/or MIC 2; and reading the transmitter percentage of modulation
from the HP8920 Communications Test Set.

Procedure:
1. Set the HP 8920 as listed below. Use Figure 3 and Figure 4 as guides.
Press PRESET
Press TX function
Using the CURSOR control knob or the USER key’s set:
AUTO MANUAL MANUAL

Apollo SL40 Field Maintenance Manual 15

Troubleshooting

TUNE Freq 127.5 MHz

TX PWR 0
RF IN/ ANT RF IN
AF ANAL IN AM Demod
De-EMPHASIS off
Detector PK+-/2
AF GEN Freq 1 kHz
Set AF GEN LVL 100 mV and to on
2. Set the SL40 as listed below:
While viewing the frequency display, use the large and small knob on the right
side of the SL40 to select 127.5 MHz.
Toggle this frequency into the Active channel.
Press the PTT button on the test panel.
EXPECTED RESULTS % modulation > 90%
Set AF GEN. LVL 50 mV
EXPECTED RESULTS % modulation > 70%
3. UN key the transmitter.
4. Repeat Steps 1 through 3 for the other MIC jack.

TRANSMITTER SNR (SIGNAL TO NOISE RATIO)

SNR is measured using the HP8920. This is accomplished by presetting the SL40 to the
same channel as the HP8920. Adjust the amplitude of a 1000 Hz tone (input to MIC 1
and/or MIC 2) to obtain 85% modulation. Select the SNR function and the HP8920
Communications Test Set will perform this test automatically.

Procedure:
1. Set the HP 8920 as listed below. Use Figure 3 and Figure 4 as guides.
Press PRESET
Press TX function
Using the CURSOR control knob or the USER keys set:
AUTO MANUAL MANUAL
TUNE Freq 127.5 MHz See NOTE below
TX PWR 0
RF IN/ ANT RF IN
AF ANAL IN AM Demod
De-EMPHASIS off
Detector PK+-/2
AF GEN Freq 1 kHz
Set AF GEN LVL to read 85% modulation
Set AF meter to SNR

16 Apollo SL40 Field Maintenance Manual

 Troubleshooting

2. Set the SL40 as listed below:

While viewing the frequency display, use the large and small knob on the right
side of the SL40 to select 127.5 MHz.
Toggle this frequency into the Active channel.
Press the PTT button on the test panel.
3. Key the transmitter
EXPECTED RESULTS SNR ≥35 dB
4. UN key the transmitter

TRANSMITTER AUDIO DISTORTION

Transmitter audio distortion is measured using the HP8920. This is accomplished by
presetting the SL40 to the same channel as the HP8920. Adjust the amplitude of a 1000
Hz tone (input to MIC 1 and/or MIC 2) to obtain 85% modulation. Then select the audio
distortion function on the HP8920 Communications Test Set.

Procedure:
1. Set the HP 8920 as listed below. Use Figure 3 and Figure 4 as guides.
Press PRESET
Press TX function
Using the CURSOR control knob or the USER keys set:
AUTO MANUAL MANUAL
TUNE Freq 127.5 MHz
TX PWR 0
RF IN/ ANT RF IN
AF ANAL IN AM Demod
De-EMPHASIS off
Detector PK+-/2
AF GEN Freq 1 kHz
Set AF GEN LVL to read 85% modulation
Set AF meter to DISTN
2. Key the transmitter
EXPECTED RESULTS: DISTN < 10%
3. UN key the transmitter

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Troubleshooting

RECEIVER

RECEIVER PERFORMANCE
The following specifications define expected receiver performance.
Class D
Frequency range 118.000 to 136.975 MHz, 760 channels.
Sensitivity 1µV (2µV hard) for 6dB S+N/N with 30% modulation at
1000Hz
Selectivity <6dB variation at ±7kHz > 60dB at 22kHz
Speaker audio output level 12 watts into 4Ω load., 8 watts into 8Ω load.
Headphone audio output level 280mW into 100Ω load, 120 mW into a 500Ω load.
Distortion <5% at rated audio output.
AGC characteristics <3dB variation in audio output from 5 µV to 100mV
input, 15% to 90% modulation.
Squelch control Automatic squelch with manual override

SPEAKER AUDIO TEST

The speaker audio level is measured using the HP8920. This is accomplished by
connecting the speaker audio to the Audio in, (high) of the HP8920. By adjusting volume
control to the desired level, (12W) and measuring the audio power in watts.

Procedure
1. Set the HP 8920 as listed below. Use Figure 3 and Figure 5 as guides.
Press PRESET
Press RX function
Using the CURSOR control knob or the USER keys set:
AUTO MANUAL MANUAL
RF GEN Freq 127.50 MHz
AF GEN Freq 1 kHz
Amplitude 10,000 µ volts
RF OUTPUT RF OUTPUT
AF Freq 1000 / 85%
Ext Load 4 ohms
AC LEVEL units to Watts

2. Connect the speaker load to the HP8920 audio in. Turn the SL40 volume control to
show an output level of 12 watts on the HP8920. Record the Speaker 1000 Hz Distortion
at 12 watts. Value should be < 5%. Set the distortion level to Reference
3. Connect the headset load to the HP8920 audio in. Turn SL40 volume control to show
an output level of 280 m watts on the HP8920. Record the Headset 1000 Hz Distortion at
280 m watts. Value should be < 5%. Set the distortion level to Reference

18 Apollo SL40 Field Maintenance Manual

 Troubleshooting

Figure 5. Receiver Test Setup

RECEIVER SENSITIVITY
The speaker audio level is measured using the HP8920.

Procedure
1. Set the HP 8920 as listed below. Use Figure 3 and Figure 5 as guides.
Press PRESET
Press RX: function
Using the CURSOR control knob or the USER keys set:
RF GEN Freq 118.00 MHz
Amplitude 1,000 µ volts
RF OUTPUT RF OUTPUT
AF Freq 1,000 / 85%
Ext Load 4 ohms
AC LEVEL W
2. Connect speaker load to the HP8920 audio in. Set SINAD low level to 4 dB (LO=4).
Turn SL40 volume control until AC LEVEL on HP8920 reads 12 watts.
3. The distortion level on the HP8920 should be < 5%.
4. Reduce the AF Freq. modulation level on the HP8920 to 30 The distortion level on the
HP8920 should be < 5% and the noise level should be ≥ 25 dB.
5. Disable the squelch by pulling out on the volume knob. Reduce the signal generator
amplitude until the HP8920 displays a 6 dB SINAD value (S+N/N). The amplitude level
should be <1— volt.

Apollo SL40 Field Maintenance Manual 19

Troubleshooting

UNIT DISASSEMBLY / REASSEMBLY

DISASSEMBLY
Perform the procedures in the following paragraphs to disassemble the SL40. All
disassembly must be performed in an ESD safe work area (see guidelines on Page 5)
using ESD safe working techniques.
Com Main Board Removal
1. Place the SL40 on a properly grounded work surface.
2. Using a #2 Phillips head screwdriver, remove the nine 4-40x3/16” flat head screws
securing the cover to the chassis.
3. Lift the back end of the cover and slide it towards the rear of the chassis until it is
clear of tab on the display bezel, then remove the cover.
4. Disconnect the ribbon cable connector from J603 on the Com Main board.
5. Using a #2 Phillips head screwdriver, remove the ten 4-40x1/4” panhead screws and
lockwashers securing the Com Main board to the chassis.
6. Using a #2 Phillips head screwdriver, remove the two 4-40x1/4” flathead screws
securing the 15-pin d-sub connector to the back of the chassis.
7. Using a 9/16” deep well socket, remove the jam nut and internally toothed lockwasher
securing the BNC connector to the back of the chassis.
8. With the board positioned tightly against the back of the chassis, tilt up the front of the board
until it is clear of the bezel then slide the board forward to remove it from the chassis.
NOTE: There is a small notch in the upper right corner of the Com Main board
(See Figure 6 ) that allows the board to just clear the tab on the display
bezel when the board is properly positioned. If more that a very slight
forward pressure on the bezel is required to remove the Com Main board,
check the position of the board in the chassis and ensure that the notch is
aligned with the tab on the bezel.

NOTCH

COM MAIN BOARD

Figure 6. Com Main Board Outline

CAUTION: Do not force the board or apply excessive force to the display
bezel.

20 Apollo SL40 Field Maintenance Manual

 Troubleshooting

Com Display Board Removal

1. Place the SL40 on a properly grounded work surface.
2. Using a #2 Phillips head screwdriver, remove the nine 4-40x3/16” flat head screws
securing the cover to the chassis.
3. Lift the back end of the cover and slide it towards the rear of the chassis until it is
clear of tab on the display bezel, then remove the cover.
4. Disconnect the ribbon cable connector from J1 on the Com Display board.
5. Using a #2 Phillips head screwdriver, remove the three 4-40x1/4” flat head screws
(one on each side and one on the bottom) that secure the display bezel to the chassis
and remove the bezel.

REASSEMBLY
Perform the procedures in the following paragraphs to reassemble the SL40. All
reassembly must be performed in an ESD safe work area (see guidelines on Page 5) using
ESD safe working techniques.
Com Main Board Replacement
1. Tilt the Com Main board to allow the connectors to go through the holes in the back
of the chassis.
2. Ensure that the notch in the upper right corner of the board (see Figure 6) is aligned with
the tab on the display bezel and push the board down into the chassis. If more that a very
slight forward pressure on the bezel is required to replace the Com Main board, reposition
of the board in the chassis and ensure that the notch is aligned with the tab on the bezel.
CAUTION: Do not force the board or apply excessive force to the display
bezel.
3. Ensure that the holes in the board are aligned with the matching holes in the chassis.
Start 1 or 2 screws to maintain alignment.
4. Secure the 15-pin d-sub connector to the rear of the chassis using two 4-40x1/4” flat
head screws.
5. Using a 9/16” deep well socket, fasten the BNC connector to the rear of the chassis
with a nut and internally toothed lockwasher.
6. Secure the Com Main board to the chassis using ten 4-40x1/4” pan head screws and
lockwashers.
7. Reconnect the ribbon cable from the display board to J603 on the Com Main board.
8. Tilt the SL40 cover so the front edge slides under the tab on the display bezel, and
position the cover so the screw holes are aligned with the PEM nuts. Secure the cover
with nine 4-40x3/16” flat head screws.
Com Display Board Replacement
1. Position the bezel assembly on the front of the chassis so that the screw holes in the
bezel align with the holes in the chassis, and secure the bezel in position using three
4-40x1/4” flat head screws, one on each side and one on the bottom.
2. Reconnect the ribbon cable from the Com Main board to J1 on the Com Display
board.

Apollo SL40 Field Maintenance Manual 21

Troubleshooting

3. Tilt the SL40 cover so the front edge slides under the tab on the display bezel, and
position the cover so the screw holes are aligned with the PEM nuts. Secure the cover
with nine 4-40x3/16” flat head screws.

REPLACEABLE COMPONENTS
The SL40 field replaceable components are listed by II Morrow part number in Table 1.
Replacement policy and information on proper packaging of the SL40 components for
shipment is given in subsequent paragraphs.

COMPONENT LISTING
The components of the SL40 that are considered to be field replaceable and for which test
and replacement procedures are provided are listed in Table 1.

Table 1 Replaceable Components

430-6040-2xx Apollo SL40 Comm Transceiver
Part # Description Qty
*415-7000-10 SP96 Com Display Board 6010 1
415-7002-00 VHF Com Main Board 6011 1

*Although the Com Display board is the actual replaceable component, assembly
considerations dictate that the complete Display assembly be returned for replacement.

REPLACEMENT POLICY
When troubleshooting procedures identify a failed component in the SL40, contact the
II Morrow Service Department for a Return Material Authorization (RMA) number and
shipping instructions. Do not return the component without an RMA. Instructions for
contacting the factory are given on page 22

PACKAGING FOR SHIPMENT

The SL40 circuit boards are subject to both mechanical and electrical damage when
improperly handled. These components must be packaged for shipment in anti-static
bags, to protect against electrostatic damage, and a sturdy protective box, to prevent
mechanical damage during shipment. Ideally, the component to be returned should be
packaged in the same shipping material that the replacement component is shipped in.

CONTACTING THE FACTORY FOR ASSISTANCE

If the Apollo SL40 unit fails to operate despite troubleshooting efforts, contact the II Morrow
factory for assistance.
II Morrow Inc.
2345 Turner Rd. SE
Salem, Oregon 97302
USA

22 Apollo SL40 Field Maintenance Manual

 Troubleshooting

Phone (503)581-8101 or 1-800-525-6726

Be prepared with the following information about the installation:

• Installation configuration (accessories, antenna, ...)
• Model number, part number with mod levels, and serial number
• Software versions
• Description of problem
• Efforts made to isolate the problem
• other installed avionics

Apollo SL40 Field Maintenance Manual 23

Troubleshooting

NOTES

24 Apollo SL40 Field Maintenance Manual

 Checkout Procedures

SECTION 3 - CHECKOUT PROCEDURES

GENERAL
This Section provides procedures for final verification and checkout of the SL40 prior to
returning the unit to service. During the checkout, the Test Data Sheet described in
Appendix A is to be filled out. If all items check out properly, the unit may be reinstalled
in the aircraft and returned to service.

SERVICE VERIFICATION
Verify that unit has been repaired properly, all components have been reinstalled and
properly secured, and that all functions are set as required. Note the date the repairs were
completed, components replaced, technician who performed the repair and any other
pertinent details on the Test Data Sheet.

FUNCTIONAL CHECKOUT
After replacement of the faulty component and before reinstalling the SL40 in the aircraft,
retest the unit to ensure that all functions are operating properly.

DISPLAY CHECK
Perform the display test given on Page 9. Record the test results on the Test Data Log
sheet in Appendix A.

CONTROLS TEST
Perform the controls test given on Page 10. Record the test results on the Test Data Log
sheet in Appendix A.

TRANSMITTER TESTS
Perform the transmitter tests beginning on Page 13. Record the test results on the Test
Data Log sheet in Appendix A.

RECEIVER TESTS
Perform the receiver tests beginning on Page 17. Record the test results on the Test Data
Log sheet in Appendix A.

Apollo SL40 Field Maintenance Manual 25

Checkout Procedures

NOTES

26 Apollo SL40 Field Maintenance Manual

 Appendix A

APPENDIX A - TEST DATA LOG

Once the unit is repaired and the checkout procedure on Page 25has been performed to verify
proper operation, reinstall the SL40 in the aircraft. Refer to the SL40 Installation Guide,
560-0956 for installation instructions. The steps that are not applicable to a particular
installation may be skipped.
A test data log sheet is included on page 27 to fill out during the checkout procedure. Make a
photocopy of the log sheet for ease of use if desired.

Mounting / Wiring Check

Verify that all cables are properly secured and shields are connected to the rear of the
mounting frame. Check the movement of the aircraft controls to verify that there is no
interference.

POST INSTALLATION CHECKOUT

Once the unit is reinstalled, complete the post installation checkout procedure given in the
SL40 Installation Guide, 560-0956 to verify proper operation. Refer to the Users Guide for
operating instructions.

SIDETONE LEVEL ADJUSTMENT

The sidetone volume was preset at the factory to what should be an acceptable level.
However, the level can be adjusted using the built-in test mode. To adjust the sidetone level:
1. Press and hold the ⇔ and RCL buttons while switching on the unit. This will enable the
built-in test mode.
2. Rotate the LARGE knob to display the SIDETONE LVL page.
3. Press the ⇔ (the number will flash), rotate the small knob to change the level number, and
press MEM to save the new setting. The range of the number is 000 to 255, with 128
producing one half of full rated output.
4. Turn the unit off to exit the test mode.
5. Turn on the unit, select an appropriate frequency, and key the transmitter and talk into the
microphone to check the level.

FLIGHT TEST CHECK

A flight test is recommended as a final installation verification. The performance may be
verified by contacting a ground station at a range of at least 50nm while maintaining an
appropriate altitude and over all normal flight attitudes. Performance should be checked using
low, high, and mid band frequencies.

APOLLO SL40 POST-REPAIR TEST DATA LOG Date: ___/___/___

Apollo SL40 Field Maintenance Manual 27

Appendix A

By: _____________
CONFIGURATION INFORMATION:
SL40 VHF COMM 430-6040-2__ Mod ____ Serial # ___________
Antenna: ___________
DISPLAY AND CONTROLS CHECKOUT
OK Display test
Controls
OK ⇔ Button test OK MON Button test
OK Squelch knob test OK RCL Button test
OK EC Button test OK MEM Button test

TRANSMITTER CHECKOUT:
Transmitter Frequency Error PPM @ MHz ( < 15 PPM)
Transmitter Power Watts @ MHz (> 8 Watts)
Transmitter Modulation @ 100 mV MIC 1 %@ MHz (> 90%)
Transmitter Modulation @ 50 mV MIC 1 %@ MHz (> 70%)
Transmitter Modulation @ 100 mV MIC 2 %@ MHz (> 90%)
Transmitter Modulation @ 50 mV MIC 2 %@ MHz (> 70%)
Transmitter SNR dB @ MHz (≥ 35dB)
Transmitter Audio Distortion %@ MHz (< 10%)
RECEIVER CHECKOUT:
Speaker Audio Distortion % (< 5%) Receiver Sensitivity: Distortion % (<5%)
Headset Audio Distortion % (< 5%) Noise dB (≥ 25dB)
Ampl. µvolts (<1µv)
COMMENTS:

NOTES

28 Apollo SL40 Field Maintenance Manual