Ericsson Radio MPI II VHF User Manual

LBI-38557A  
Mobile Communications  
SERVICE SECTION  
FOR  
MPI-II VHF PERSONAL RADIO  
Ericsson GE Mobile Communications Inc.  
Mountain View RoadLynchburg, Virginia 24502  
Copyright January 1991, Ericsson GE Mobile Communications, Inc.  
Printed in U.S.A.  
Maintenance Manual  
 
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BNC CONNECTOR  
PROGRAMMING  
1. Remove the No. 3-48 x .125 setscrew (D) using a 0.050  
hex tool.  
The MPI-II radio is programmed through a test cable  
connected to the accessory connector located on the side of the  
radio. Power is applied to the battery terminals located on the  
rear radio assembly. B+ should be 7.5V for a 2 watt radio and  
10.0V for a 4 watt radio.  
2. Unsolder the BNC center pin from the antenna contact.  
3. Remove the BNC connector.  
Programming information must be written to the person-  
ality PROM before alignment or performance tests. This is  
always done through the accessory connector and cable. This  
cable may be attached to the radio and left connected during  
the entire test procedure.  
UDC COVER  
Remove the M2.5-0.45 screw using a flat blade screw-  
driver or the edge of a coin.  
The assigned frequencies to be used should be pro-  
grammed into the personality of each 2-channel radio:  
TOP COVER  
First Transmit frequency  
First Receive frequency  
Tx F1  
Rx F1  
1. Pull off the two knobs from the ON/OFF/VOLUME  
and the Squelch control.  
Second Transmit frequency  
Second Receive frequency  
Tx F2  
Rx F2  
2. Remove the Spanner nuts (E) using a Spanner Tool  
ST2311.  
The radio’s chosen options must alos be programmed in:  
Channel Guard (with C.G. frequency)  
No Channel Guard  
3. Remove the 1/4-40 (F) nut using a 5/16 wrench.  
4. Remove the top cover from the T/R assembly.  
Digital Channel Guard (with D.C.G. code)  
Figure 2 - Disassembly  
SIDE PANEL  
Type 99 Tone (with Tone A Frequency, Tone B Fre-  
quency)  
FRONT COVER  
1. Remove the two Audio Jack Spanner nuts (G) using a  
Spanner Tool ST2312.  
Talk-around (enable, disable)  
STE (enable, disable)  
CAUTION  
1. Remove the battery as described in the previous  
section.  
2. Remove the side panel from the T/R Assembly.  
When separating the Synthesizer and Transmit/Re-  
ceive boards, care should be taken not to bend the  
connector pins.  
Channel Busy Inhibit (enable, disable)  
2. Remove the two screws at (A) (See Figure 2).  
3. Carefully lift the front cover from the radio.  
Detailed programming instructions should be followed as  
found in the TQ-3351 Programming Manual.  
PERSONALITY PROGRAMMING  
The MPI-II Personal Radio is equipped with a 256 x 8 bit  
serial personality EEPROM. All cutomer information such as  
the customer frequencies, customer tones and customer op-  
tions are stored in the EEPROM. The EEPROM contains all  
information to tailor the operation of the radio to the user’s  
requirements. The EEPROM is programmed by using an IBM  
compatible personal computer with MSDOS, Interface Box  
19D438367G1, RS-232 Cable 19B235027P1, Programming  
Cable TQ-3352 and Programming Software TQ-3351.  
4. Unplug the cable between the front cover MIC Board  
and the T/R Board.  
REAR COVER  
ALIGNMENT AND TEST  
1. Remove the screw at (C) using a No. 7 TORX screw-  
driver (See Figure 2).  
5. To gain access to the microprocessor, remove the  
three screws at (B) and lift up the cover.  
Initially, the Receiver of the MPI-II Personal Radio is  
aligned and ready for use before leaving the factory. The  
Transmitter is tuned at the high end of the band, with retuning  
recommended for optimum operation when another frequency  
is selected. This section provides procedures for aligning and  
testing the MPI-II VHF (136-174 MHz) Personal Radio.  
2. Remove the four M2 pan head screws, 3 at (B) and 1  
at (H), on the component side of the T/R Board using  
a No. 7 TORX screwdriver.  
SYNTHESIZER BOARD  
The Synthesizer Board may be separated from the  
Transmit/Receive Board by prying the connectors straight  
out from the pins.  
3. The RF Board with the top cover and the side panel  
attached may now be removed from the rear cover.  
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Several tests are presented which will help isolate a pos-  
Connect the leads of the dummy battery to the two  
battery terminals accessble in the open radio. The external  
power leads from the dummy battery will be connected later.  
Connect the TQ-0613 Test Box to the radio using the UDC  
connector. An audio oscillator can be used as an audio input  
to the Text Box. Connect a distortion analyzer to the audio  
output of the Test Box. For transmitter operation, an RF  
power meter/modulation analyzer should beconnected to the  
antenna connector J3 in place of the antenna. A frequency  
meter can be coupled to the output using a coaxial directional  
coupler. For receiver operation a frequency modulated RF  
signal generator should be connected to J3.  
1. With the highest transmitter frequency selected, tune  
C118, C124, C126 formaximum output power meas-  
ured with the Power Meter. The power out should be  
greater than 4.5 watts with 10V supply and greater  
than 2.5 watts with 7.5V supply.  
Special Equipment  
sible RF or control circuit problem. The control circuits, which  
are located on the T/R Board, contain no adjustments and there  
is no alignment required for the control circuits. See the Trou-  
bleshooting section for test information if a problem is sus-  
pected in the control circuits.  
1. IBM Compatible Computer with MS-DOS  
2. Interface Box 19D438367G1  
3. RS-232 Cable19B235027P1  
2. Adjust C126 for minimum DC current drain from the  
power supply until the power output is 4.2-4.3 watts  
for 10V supplies and 2.2-2.3 watts for 7.5V supplies.  
TEST EQUIPMENT  
General Equipment  
4. Programming Cable TQ-3352  
5. Programming Software TQ-3351  
6. Synthesizer Extender Cable  
3. Adjust C118 for minimum DC current drain from the  
power supply until the power output is 4.0-4.1 watts  
for 10V supplies and 2.0-2.1 watts for 7.5V supplies.  
For programming, the TQ-3301 serial programmer  
would alternatively be connected through the UDC connec-  
tor on the side of the radio.  
1. RF Generator (136-174 MHz)  
2. Wattmeter (5 watts)  
3. Ammeter (2 amperes)  
4. Distortion Analyzer  
5. Frequency Counter  
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4. Tune C124 for maximum outut power.  
7. Discharge Analyzer  
5.  
Return C126 for 1050 mA (±10 mA) for 10V sup-  
plies and 750 mA (±10 mA) for 7.5V supplies. Check  
the output power. The output power should be equal  
to or greater than the minimum power as listed in the  
table above.  
8. Alignment Tool, 0.1" slotted (metal) tips  
9. Alignment Tool, 0.1" slotted tips.  
Set the DC power supply to 7.5 volts(±0.1 volts) for a 2  
watt radio, or 10 volts (±0.1 volts) for a 4 watt radio. Connect  
the power supply to the dummy battery as shown in Figure  
3.  
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TEST SET UP  
Customer Programming And Wide Band  
Tuning  
TRANSMITTER ALIGNMENT  
6. Test Box TQ-0613  
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To gain access to adjustable circuit components for align-  
ment of the radio, the front cover must be removed as described  
in the Disassembly Section. A test setup should be arranged as  
shown in Figure 3.  
7. Test Cable 19C851752P8  
With the test setup for transmitter operation in place,  
select the highest transmit frequency and key the radio ON  
to find an indication of output power on the power meter.  
See Figure 4 for the location of tuning controls and test  
points.  
This section describes the programming and adjust-  
ments for wide band tuning. The following steps (1-4) are  
for preset customer frequencies with:  
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Up to 10 MHz spread with no degradation from Pref  
Frequency Set  
Up to 17 MHz spread with less than 1 dB of degra-  
dation from Pref in the 136-153 MHz band  
Measure the frequency of the RF output signal with the  
frequency meter. It should be within ±100 Hz of the pro-  
grammed frequency. Should a small adjustment be neces-  
sary, this change can be made by tuning the Reference  
Oscillator (TCXO) module U203 on the Synthesizer Board.  
or  
Up to 24 MHz spread with less than 1 dB of degra-  
dation from Pref in the 150-174 MHz band  
1. Frequency spreads greater than 10 MHz only -  
Program the radio on a channel mid way between the  
two desired frequencies. Tune the radio by following  
Steps 1-5 in the Set Transmitter Power section. Then  
reprogram the customer frequencies and measure the  
power out on the upper channel. Go to Step 2.  
Set Transmitter Power  
The following sequence should be followed for maxi-  
mizing rated output power:  
Frequency spreads less than or equal to 10 MHz  
only -Program the radio on the customer frequen-  
cies. Tune the radio onthe higher frequency channel  
by following Steps 1-5 in the Set Transmitter Power  
section.  
Table 1 - Minimum Output Power  
2 WATT  
RADIOS  
4 WATT  
RADIOS  
Battery or Supply  
Voltage  
7.5  
VOLTS  
10  
VOLTS  
Minimum Output  
Power  
1.9  
WATTS  
3.8  
WATTS  
Figure 3 - Test Setup  
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Figure 4 - Location of Tuning Controls and Test Points  
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2. Check power on the lower channel. Adjust C124 in the  
NOTE  
Second LO Frequency Set  
Tabel 2 - General Troubleshooting Guide  
direction that increases power output to a level half way  
between the initial lower and upper channel levels.  
Throughout the service procedures, the following  
information should be observed:  
Remove all modulation from the input signal and increase  
the level to 0 dBm. Monitor the frequency at J501 and adjust  
L505 in the crystal oscillator circuit for 455 kHz ±100 Hz.  
SYMPTOM  
POSSIBLE CAUSES  
3. Recheck the upper channel power. If the upper channel  
power is reduced, reset to the previous level by adjust-  
ing C126.  
Completely inopera-  
tive (no audio)  
Dead Battery Pack  
Fuse blown  
Control circuit problem  
The bench power should be set for 7.5 Vdc  
(±0.1 Vdc) for a 2 watt radio, or 10.0 Vdc (±0.1  
Vdc) for a 4 watt radio. If a battery pack is  
used, it should be fully charged. Typical battery  
pack voltage should be within ±20% of set  
voltage over its full discharge cycle.  
Quadrature Detector Set  
4. Repeat this procedure until the power out on both  
channels is equal (±.1W).  
At power-up radio  
beeps continuously  
Weak battery pack  
Unit is not programmed  
Synthesizer is not locked  
Modulate the RF input signal with a 1 kHz tone at 3 kHz  
peak deviation. Load the speaker output at the accessory con-  
nector with 8 ohms to ground. Monitor the speaker output from  
the accessory connector while tuning L506 in the quardrature  
detector for a maximum audio level.  
For frequency spreads 10 MHz - power out ≥  
power minimum  
Logic Levels should be:  
Logic 1 = high 4.5 Vdc  
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Receiver inoperative  
or weak  
Squelch level set too high  
Channel Guard enabled  
Defective antenna  
For frequency spreads > 10 MHz - power out ≥  
power minimum - 1dB  
Logic 0 = low 0.5 Vdc  
Modules are not field repairable. Schematics  
and Outline drawings for the modules are pre-  
sented for troubleshooting reference only.  
L.O. Notch Tuning  
Supply current levels should not exceed 1100 mZ  
(10V) or 800 mA (7.5V) with wide band tuning.  
T/R Board problem  
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When it necessary to limit the L.O. leakage out the antenna  
port to a level less than -60 dBm, (Canadian D.O.C. RSS 119,  
121 require -53 dBm for portables with batteries, otherwise -57  
dBm) the L.O. notch filter may be tuned to the receiver L.O.  
frequency to meet this requirement. Observe the L.O. signal  
level at the antenna port on a spectrum analyzer capable of  
reading -70 dBm. Select the channel with the lower operating  
receive frequency and tune the notch filter adjustable capacitor  
(C136) for a minimum level. Check the level on the higher  
receive frequency. If greater than -60 dBm, turn the capacitor  
(C136) in the direction that lowers the level to the point that  
-60 dBm is reached and stop. Recheck the lower receive  
frequency.  
Transmitter inopea-  
tive or low range  
The personality information stored in the radio  
should be backed up on the PCcomputer before  
any service procedure.  
Power levels set too low  
Weak battery  
Defective antenna  
T/R Board problem  
TX Modulation Set  
With the transmitter keyed, apply a 1 kHz tone at 100 mV  
RMS to the MIC input. Adjust R230, located on the Synthe-  
sizer Board, until the following peak deviation is measured on  
the output modulation analyzer:  
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Tx and Rx inopera-  
tive on one or both  
channels  
Programming incorrect  
Synthesizer problem:  
VCO, prescaler, or  
lock detect  
Documentation To Help In Troubleshooting  
With Channel Guard - 4.5 kHz (±100 Hz)  
Without Channel Guard - 3.75 kHz (±100 Hz)  
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RX and TX block diagrams with RF gains and  
levels  
troubleshooting a personal radio. Current consump-  
tion offers an excellent clue in the case of a dead or  
weak transmitter. See Table 3 in the Battery Informa-  
tion section on typical current consumption for dif-  
ferent operating conditions. Check supplies as  
follows:  
Synthesizer block diagram  
Control Circuits block diagram  
Audio Processing block diagram  
Interconnection diagram  
Outline diagrams  
RECEIVE ALIGNMENT  
TROUBLESHOOTING  
Change to a receiver test setup, with a frequency modu-  
lated RF signal generator connected to the antenna jack J3. Set  
the input RF signal to the highest programmed receive fre-  
quency and modulate it with a 1 kHz tone at 5 kHz peak  
deviation. Use a signal level high enough to measure the level  
of the 455 kHz 2nd IF signal at test point J501 with an RF AC  
voltmeter. Proceed with the following alignment procedure.  
This section provides a guide to troubleshooting the MPI-  
II VHF radio. The following procedures will assist in de-  
terming if the problem is in the RF circuits (Transmitter,  
Receiver or Synthesizer) or the Control circuits. The test set-up  
should be the same as that used in the Alignment section of this  
manual.  
a. Check for battery B+ voltage at J12-01, or inside  
fuse F1/switch S1. It should be present at the  
driver Q104 and final amplifier Q105, and meas-  
ure 7.5 Vdc for 2-watt radio, 10 Vdc for 4-watt  
radio.  
Schematic diagrams  
Parts lists  
IC data  
IFAlignment  
b. Check for presence of B+ SW on buffer ampli-  
fier Q106 and predriver Q103. It should switch  
ON under control of the PTT switch through B+  
switch Q805.  
Adjust the RF signal level for linear operation at J501.  
Tune L502 and L504 for a maximum IF signal level at J501.  
TRANSMITTER  
An alternate method for making the IF alignment is as  
follows. Tune L502 and L504 for minimum audio distortion  
while monitoring the speaker output. Use either 5 kHz or 3 kHz  
of deviation.  
c. Check 5.4 V from 5.4 V regulator, which is  
required for and available on the Synthesizer  
board.  
Transmit Power Output Problem, Inoperative  
or Low  
1. Power sources and regulated power supplies should  
be checked before troubleshooting any transmitter  
problem. The radio’s power source, whether abattery  
or bench power supply, is especially important in  
2. An early step in troubleshooting for the cause of low  
RF output power is to check that the programming is  
correct.  
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3. Check for proper operation of the synthesizer. There  
Check to see that Channel Guard signal is at the  
output of the post limiter filter, U301-A pin 1, or  
at the TX MOD output.  
8. If a sensitivity problem ora distortion problem remains,  
then a receiver RF and IF alignment should be done  
using the recommended procedures in the alignment  
section.  
Receive Audio Problem, Low Audio Level Or No  
Audio  
should be approximately 0 dBm drive level on the  
SYNTH output line for proper transmit operation. If  
a Syntheiszer problem is suspected, following the  
suggestions in Troubleshooting Synthesizer section.  
The following steps are suggested to locate the trouble:  
1. Be sure the programming is correct.  
4. If the TX MOD output is proper from the T/R Board,  
then check to see if the audio signal is arriving at the  
Synthesizer Board. If so, on the Synthesizer Board:  
Receiver Squelch Problem  
4. If current consumption appears normal, and the syn-  
thesizer output level is correct, check that the DPTT  
and BAND SW lines are in the proper state. The  
problem may be in the antenna T/R switch circuit  
with diodes D101, D102 or in the antenna connector  
W1. A problem in the antenna switch circuit or the  
antenna connector may also cause the receiver to be  
weak.  
2. Check to see if the receiver is unsquelched with strong  
on-channel signal: CAS is low, as controlled by SQ  
POT R619.  
a. Check to see if the audio is at Mod Pot R230 pin  
1.  
1. Check for presence of noise at VOL SQ HI line when  
no received RF carrier is present.  
b. Check to see if the audio level at the centertap of  
Mod Pot R230 changes with pot setting.  
2. In the squelch noise path check for presence of filtered  
noise at output of high pass filter U501 pin 11.  
3. Check the RX MUTE and MUTE gates are in correct  
states.  
c. Check that the audio signal is arriving at the  
VCO U204 pin 3.  
3. Check to see if the noise level at U501-11 decreases  
when a RF signal is input to the receiver.  
4. In the voice path check that audio is reaching the output  
stage U602-B pin 7, and its output on pin 1.  
5. If the synthesizer drive level seems normal, but cur-  
rent consumption is low, the transistor stages in the  
transmitter RF chain should next be checked, begin-  
ning with the final amplifier Q105.  
4. With no carrier, be sure noise is present at pin 1 of  
squelch pot R619, and also at U603 pin 12 when  
squelch pot is rotated.  
5. Check that power is applied to audio amplifier U602-B  
pin 2.  
RECEIVER  
Receiver problems will generally only be found on the  
T/R Board, in the following sectors:  
6. Check that audio is reaching the speaker through the  
Accessory Jack Board.  
Transmit Audio Problem  
5. Check that the DC level of the filtered noise output  
measured at U603-B pin 6 varies with RF signal level.  
1. For a transmit audio problem the trouble could be  
either in the Syntheiszer Board or the T/R Board.  
Monitoring the TX MOD line for correct audio  
should identify which.  
Receiver RF circuitry beginning at antenna jack J3  
7. Check that when channel guard is used the tones are  
found on the TN DATA line. When T99 tones are used  
they should be at TN DATA.  
6. Make certain that a threshold voltage is present at  
comparator input U603-B pin 5.  
Receiver IF circuitry, 45 MHz 1st IF and 455 kHz  
2nd IF  
7. Check to see if the CAS line switches low when a RF  
signal carrier is introduced.  
8. Check that data reaches the microprocessor, and that  
the receiver is unmuted when correct limited tone chan-  
nel guard data or correct Type 99 tones are decoded.  
Source of audio signals beginning at the quadrature  
detector output in U501  
2. If the problem seems to be on the T/R Board, then try  
the following steps:  
8. Check that the DC level at the threshold terminal U603-  
B pin 5 increases when the voltage of the CAS line  
increases.  
Three paths of audio processing beginning with the  
VOL SQ HI signal:  
a. Check to see if the MIC output is reaching the  
T/R Board.  
9. If digital channel guard is being used, check to see if  
the polarity is correct.  
1. Voice path, through to the speaker output  
2. Squelch noise path, through to CAS output  
3. Tone data path, through TN DATA output  
9. Make certain that the CAS line switching voltage  
reaches the microprocessor input U701 pin 13.  
b. Check to see if the audio is present at the pre-  
amplifier output, collector of Q301.  
Receiver Sensitivity Problem  
c. Check to see if the audio is present at the audio  
limiter output, U301-D pin 14.  
1. Check that 5.4 V, RX 5.4 V, SYNTH 5.4 V, and VREF  
are present where indicated.  
SYNTHESIZER  
Microprocessor and circuitry controlled by it, in-  
cluding synthesizer  
d. Check to see if the MIC MUTE line is in the  
proper state, low for not muted.  
Troubleshooting the synthesizer circuit consists of first  
checking for the proper D.C. levels. Then determing if proper  
waveforms are present and checking individual modules.  
When the channel switch or the PTT switch is operated, the  
SYN ENABLE, SYN DATA and SYN CLK should become  
active. Monitor these lines and troubleshoot the Transmit/Re-  
ceive Board if activity does not occur.  
2. Check to see if the antenna clip W1 is soldered to the  
center pin of BNC antenna connector J3.  
Speaker, at final output  
e. Check that the PTT is arriving at the microproc-  
essor U701 pin 7. This is the command to gen-  
erate the DPTT and BAND SW signals along  
with the MIC MUTE signal.  
3. Check that DC voltages in the RF stages are correct.  
(Refer to the schematic diagram in LBI-38555).  
NOTE  
4. Check that RF gains are correct. (Refer to Block Dia-  
gram in LBI-38555).  
3. If Channel Guard is to be transmitted, then:  
To facilitate testing of receiver problems, the bat-  
tery saver mode can be disabled by shorting the  
TEST input to the microprocessor to ground during  
power-up. The radio can be taken out of test mode  
by recycling the power without TEST grounded.  
TX Modulation  
5. Check to see if the first and second LO injection fre-  
quencies are correct.  
a. Check to see if Channel Guard is being gener-  
ated at CG ENC output by microprocessor  
switching outputs U701 pins 34-37.  
Check to see if the audio is at pin 1 of the Mod Pot R230.  
The audio level at pin 2 of the Mod Pot should change when  
the pot is rotated. Finally, check to see if the audio signal is  
arriving at pin 5 at U206.  
6. Check for proper LO injection signal levels.  
b. Check to see if the Channel Guard signal is at  
the output of the Tx Channel Guard low pass  
filter U603-A pin 1.  
7. Check to see if the quadrature detector is tuned for  
maximum audio output level at the speaker when an  
input RF signal is modulated with a 1 kHz tone at 3 kHz  
peak deviation.  
c.  
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D.C. Analysis  
Bilateral Switch U205  
CAUTION  
Battery voltage (7.5/10 Volts, B+) is supplied to a 5.4 volt  
Bilateral switch U205 is used to short around parts of the  
loop filter during channel changes. A shorted gate (to ground  
or adjacent gate) may be isolated by comparing voltages  
through the loop filter to those of a functioning radio. Defective  
gates might be suspected when the radio does not change  
frequency quickly enough.  
regulator circuit consisting of transistors Q801, Q802 and  
Q803. Diode regulator U801 provides a 2.5 volt reference for  
this circuit. Battery voltage (B+) is also supplied to the Syn-  
thesizer Board for isolation amplifier U206. the 5.4 volt regu-  
lator supplies both the synthesizer and most of the Transmit  
and Receive circuits.  
The CMOS Integrated Circuit de-  
vices used in this equipment can be  
destroyed by static discharges. Be-  
fore handling one of these devices,  
the serviceman should discharge  
himself by touching the case of a bench test instru-  
ment that has a 3-prong power cord connected to an  
outlet with a known good earth ground. When sol-  
dering or desoldering a CMOS device, the solder-  
ing equipment should have a known good earth  
ground.  
Figure 8 - SYN EN (Input to Pin 13 of U201)  
COMPONENT REPLACEMENT  
SURFACE MOUNT COMPONENTS  
The BAND SW control input, initiated from the Trans-  
mit/Receive Board, is used to bandswitch the VCO. This input  
is low when receiving and high (greater than 3 volts) when  
transmitting.  
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NOTE  
Surface mount components should always be replaced  
using a temperature controlled soldering system. The solder-  
ing tools may be either a temperature controlled soldering  
iron or a temperature controlled hot-air soldering station. A  
hot-air system is recommended for the removal of compo-  
nents on the multi-layered boards used in the MPI-II radio.  
With either soldering system, a temperature of 700°F  
(371°C) should be maintained.  
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Waveforms associated with the synthesizer were  
measured with 10 megohms, 30 pF probe using Dc  
coupling. See Figures 5-8.  
SURFACE MOUNT REMOVAL  
Figure 5 - Reference Oscillator  
(Input to PLL Module U201, Pin 2)  
1. Grip the component with tweezers or small nee-  
dlenose pliers.  
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2. Alternately heat the metallized terminal ends of the  
surface mount component with the soldering iron. If  
a hot-air system is used, direct the heat to the termi-  
nals of the component. Use extreme care with the  
soldering equipment to preventdamage to the printed  
wire board (PWB) and the surrounding components.  
Reference Oscillator U203  
The following procedures outline the removal and re-  
placement of surface mount components. If a hot-air solder-  
ing system is employed, see the manufacture’s operating  
instructions for detailed information on the use of your  
system.  
Pin 2 of the Phase Lock Loop U201 should have a wave-  
form similar to the one shown for the reference oscillator  
(Figure 5). If this waveform is not present, oscillator module  
U203 is probably defective.  
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3. When the solder on all terminals is liquefied, gently  
remove the component. Excessive force may cause  
the PWB pads to separate from the board if all solder  
is not completely liquefied.  
Figure 6 - Fin (Input to U201, Pin 10)  
VCO U204  
CAUTION  
Transistor Q201  
Connect a DC power supply to pin 3 of U204. With 2.0  
volts DC on pin 3, the output on pin 5 of U204 should be  
approximately 140 MHz for the low split and approximately  
190 MHz for the high split. With 4.3 volts DC on pin 3, the  
output should be approximately 220 MHz for the high split.  
4. It may be necessary to remove excess solder using a  
vacuum de-soldering tool or Solderwick®Again, use  
great care when de-soldering or soldering on the  
printed wire boards. It may also be necessary to  
remove the epoxy adhesive that was under the sur-  
face mount component and any flux on the printed  
wire board.  
Avoid applying heat to the body of any surface  
mount component using standard soldering meth-  
ods. Heat should be applied only to the metallized  
terminals of the components. Hot-air systems do  
not damage the components since the heat is  
quickly and evenly distributed to the external sur-  
face of the component  
After checking for the proper operation, measure the loss  
of the VCO, pin 5 to pin 1 of the Prescaler U202. The loss  
should be 10 dB.  
The top of the ramp is approx. 0.8 Vdc geater than  
the control voltage out on pin 17 of U201.  
Power output of the VCO can be measured by connecting  
a coax cable directly to the module, between pin 5 and ground,  
through a 100 pF coupling capacitor. The output should be  
approximately 0 dBm.  
Prescaler U202  
Connect 4.3 Vdc to pin 3 to VCO U204. With the radio in  
receive, monitor the frequencies of the VCO at pin 5 through  
a 100 pF coupling capacitor. Short pin 6 to U202 to ground to  
cause divide by 65 to occur. The frequency output at pin 4  
should be the VCO frequency divided by 129. Tie pin 6 to pin  
2 (5 volts) to cause divide by 64 to occur. Check pin 4 to verify  
that this occurs. Improper division may indicate a defective  
prescaler.  
Figure 7 - Remp (Generated in  
U201 and appears on Pin 15)  
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LBI-38557  
LBI-38557  
If a hot-air system is not available, the servicetechnician  
may wish to clip the pins near the body of the defective IC  
and remove it. The pins can then be removed from the PWB  
with a standard soldering iron and tweezers, and the new IC  
installed following the Surface Mount Component Replace-  
ment procedures. It may not be necessary to "tin" all (or any)  
of the IC pins before the installation process.  
5. Check the receiver sensitivity.  
6. Check receiver audio.  
SURFACE MOUNT COMPONENT  
REPLACEMENT  
7. If not using speaker/microphone, be sure the Accessory  
Jack Cover is securely in place.  
1. "Tin" one terminal end of the new component and the  
corresponding pad of the PWB. Use as little solder  
as possible.  
BATTERY INFORMATION  
2. Place the component on the PWB pads, observing  
proper orientation for capacitors, diodes, transistors,  
etc.  
MODULE REPLACEMENT  
The MPI-II radio uses a Nickel Cadmium battery. Two  
watt radios use a 7.5 volt battery (19D900639G6) and four watt  
radios use a 10 volt battery (19D900639G7). The batteries are  
sealed at the factory and are not serviceable other than regular  
cleaning of the contacts. Table 3 below provides the current  
consumption for different operating conditions.  
The modules, all of which are located on the Synthe-  
sizer Board, are very reliable devices. Before replacing any  
of the modules, check the associated circuitry thoroughly to  
insure there is not a problem elsewhere. If replacement is  
necessary, follow the below procedures.  
3. Simultaneously touch the "tinned" terminal end and  
the "tinned" pad with the soldering iron. Slightly  
press the component down on the board as the solder  
liquifies. Solder all terminals, allowing the compo-  
nent time to cool between each application of heat.  
Do not apply heat for an excessive length of time and  
do not use excessive solder.  
Figure 9 - Typical Ni-Cad Cell Discharge Curve  
All of the component lead holes on the Synthesizer  
Board for the modules are plated through from the top to the  
bottom of the board. This allows for easy removal and  
replacement of the modules as long as appropriate soldering  
techniques are observed. Always observe static precautions  
when handling the board during module replacement.  
Table 3 - Battery Drain  
2 WATT RADIOS 4 WATT RADIOS  
With a hot-air system, apply hot air until all  
"tinned" areas are melted and the component is  
seated in place. It may be necessary to slightly press  
the component down on the board. Touch-up the  
soldered connections with a standard soldering iron  
if needed. Do not use excessive solder.  
7.5 VOLTS  
10 VOLTS  
Receiver  
Standby  
36 mA  
36 mA  
To remove a module, position the Synthesizer Board in  
a work vice (face down, chip components up) and remove  
the solder from the plated-through points at the appropriate  
pins. If a hot-air system is employed, use an appropriate tip  
that will localize the heat on the pins and not on surrounding  
chip components. Solderwick® or a vacuum de-soldering  
iron will also remove the solder if a hot-air station is not  
available. When all solder has been removed or liquefied,  
the module should drop out of the eggcrate casting.  
Receiver  
Full Audio  
200 mA  
750 mA  
200 mA  
CAUTION  
Transmit  
1050 mA  
Some chemicals may damage the internal and ex-  
ternal plastic parts of the MPI-II unit.  
REDUCED CAPACITY  
To install a module, clean any solder from the plated  
through holes and clean all flux from the board. Next, install  
the replacement module making sure that all pins align in the  
proper holes on the Synthesizer Board. Resolder the pins to  
the board. Clean the flux from the board using an approved  
solvent and clip any excess lead length.  
Nickel-Cadmium batteries in some applications can de-  
velop a condition of reduced capacity, sometimes called  
"Memory Effect". This cndition may occur when:  
4. Allow the component and the board to cool and then  
remove all fluxfromtheareausing alcoholoranother  
GE approved flux remover.  
1. The battery is continuously overcharged for long peri-  
ods of time.  
SURFACE MOUNTED INTEGRATED  
CIRCUIT REPLACEMENT  
Figure 10 - Alternate IF Option  
2. A regularly performed duty cycle allows the battery to  
expend only a limited portion of its capacity.  
PREVENTATIVE MAINTENANCE  
Any nickel-cadmium battery showng signs of reduced  
capacity, should be carefully checked before being returned  
under warranty or scrapped. If reduced capacity is suspected,  
the following procedure may restore capacity:  
If the nickel-cadmium battery is only sparingly or seldom  
used and is left on continuous charge for one or two months at  
a time, it could experience reduced capacity. This would sev-  
erly reduce the life of the battery between charges. On the first  
discharging cycle, the output voltage could be sufficiently  
lowered to reduce the battery’s hours of useful service.  
As preventative maintenance to insure that the radio is  
always operable, regularly schedule the following checks to  
be made on each radio.  
Soldering and de-soldering techniques of the surface  
mounted IC’s are similar to the above outlined procedures  
for the surface mounted chip components. Use extreme care  
and observe static precautions when removing or replacing  
the defective (or suspect) IC’s. This will prevent any damage  
to the printed wire board or the surrounding circuitry.  
1. Discharge the multicell battery at the normal discharge  
rate until the output voltage is approximately 1 volt per  
cell. For MPI-II radio batteries thisequals 6volts output  
for 2 watt radios and 8 volts output for 4 watt radio.  
1. Check the condition of and clean electrical connec-  
tions such as antenna, battery and battery charging  
contacts.  
The most common method of causing this limited capacity  
is regularly performing short duty cycles; when the battery is  
operated so that only a portion (50%) of its capacity is ex-  
pended. This type of operation can cause the battery to become  
temporarily inactive and show a severe decrease in the ability  
to deliver at full rated capacity.  
The hot-air soldering system is the best method of  
replacing surface mount IC’s. The IC’s can easily be re-  
moved and installed using the hot-air system. See the manu-  
facturers instructions for complete details on tip selection  
and other operating instructions unique to your system.  
2. Check RF power output.  
Refer to the typical Ni-Cad cell discharge curve in  
Figure 9. Note the flatness of the discharge voltage.  
Discharging below the kene of the curve does not give  
added service. Experience shows that discharging be-  
low 1.0 Volt is not necessary for reconditioning a cell.  
3. Check the transmit frequency.  
4. Check the transmit modulation.  
8
 
LBI-38557  
LBI-38557  
2. A full charge cycle using an appropriate Ericsson GE  
a. If there is a dot ontop ofeach crystal filter can, then  
use these dots to orient filters Z501 and Z502(See  
Figure 10)  
charger.  
3. This procedure should be repeated again. Performing  
the rated discharge and charge cycle at least twice  
should sufficiently restore the battery.  
b. If either crystal filter can does not have a dot on  
top, then the side of the can which has the part  
numberprinting will be usedfor orientation. Orient  
the marking side of Z502 toward L502 and the  
marking side of Z502 toward PTT switch S4 (see  
Figure 10).  
MODIFICATION INSTRUCTIONS  
(Alternate IF Option)  
3. The radio data file must be modified if the Alternate IF  
option is installed. MPI Synthesized (MPI-II) Radio  
Programming software version 2.0 or higher must be  
used to make this change. Toggle the Standrad IF status  
in the F7 Option field to "NO". Reprogram the radio  
with the new data file.  
To install the Alternate IF Option, follow the instructions  
shown below:.  
S
E
R
V
I
1. Remove 2nd oscillator crystal unit Y501 and install  
45.755 MHz crystal unit (19B233066G18)  
4. Refer to the Receiver Alignment procedure in this  
manual. Start at the beginning of the Receiver Align-  
ment section and follow the instructions for IF Align-  
ment and Second LO Frequency Set. the remaining  
sections may be omitted.  
2
Remove 1st IF crystal filters Z501 and Z502. Install  
45.3 MHz crystal filters (19A705613G26) using one of  
the following orientation methods:  
C
E
S
E
C
T
I
O
N
9
 

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