Motorola Radio Mcs2000 Vol 1 68p81083c20 A Manual

							 
Troubleshooting9-15 
-Check that U0653 pin 52 is 5 VDC with pulses to ground while transmitting data. Then check U0655 
(disconnect pin 1). If problem disappears and OPTION SW B+ circuit is OK (see 5.), replace U0655. If the 
OPTION SW B+ circuit is defect, D0684 should also be checked. 
4.2SB9600 BUS-, J650 pin 4 
-This signal is normally 0 V with short pulses to 5 VDC when data are sent on the bus. If it is constantly 5 
VDC or 0 V, check D0678 (most common error), Q0657 and Q0656. 
-Check that U0653 pin 52 is 5 VDC with pulses to ground while transmitting data. Then check U0655 
(disconnect pin 12). If problem disappears and OPTION SW B+ circuit is OK (see 5.), replace U0655. If 
the OPTION SW B+ circuit is defect, D0683 should also be checked. 
4.3SB9600 BUSY, J650 pin 14 
-This signal is 0 V with pulses to 5 VDC when data are sent on the bus. If it is constantly 5 VDC or 0 V, 
check D0675 (most common error) and Q0653. Check that U0653 pin 43 is 5 VDC with pulses to ground 
while sending data.
-Then check U0656 (disconnect pins 1 and 12). If problem disappears and OPTION SW B+ circuit is OK 
(see 5.), replace U0656. If the OPTION SW B+ circuit is defect, D0685 should also be checked.  
4.4SB9600 data in comparator 
-If the above voltages are correct, check U0652, Q0658 and Q0656. Finally check U0653. 
4.5Communications stops only with accessory on MIC Conn  
-If bus communication stops working only when an accessory is connected to the MIC Connector 
(P0651), check the OPTION SW B+ circuit (See 5.). The accessory is either defect or incompatible.  
5OPTION SW B+/Multiplexing of MIC Connector 
Normal mode = No or simple microphone connected.
SB9600 mode = Smart accessory with serial bus connected. 
5.1SW B+ in Normal mode 
-Make sure no accessory is connected to the MIC Connector (P0651).
-With power connected to the control head on J0650 pins 17 and 18, check that the DC voltage on P0651 
pin 1 is approx. 12 VDC. If not check Q0662. 
5.2Multiplexer in normal position 
-Check that the voltage on U0655/U0656 pin 10 is 5 VDC. If this fails, check Q0662 and Q0663. 
5.3PTT input 
-Check that the voltage on U0653 pin 46 changes from 5 VDC to 0 V when P0651 pin 6 is connected to 
ground (equivalent to pressing PTT on a standard microphone). 
-If this fails, check U0655. 
5.4Monitor input 
-Check that the voltage on U0653 pin 45 changes from 5 VDC to 0 V when P0651 pin 3 is connected to 
ground.
-If this fails check U0656. 
5.5AUX input 
-Check that the voltage on U0653 pin 5 changes from 5 VDC to approx. 0 VDC when P0651 pin 7 is 
connected to ground.
-If this fails check U0655. 
5.6SW B+ in SB9600 mode 
-Connect a 5.6 kohm resistor from P0651 pin 1 to ground (a keypad microphone can be used instead).
-Check that the DC voltage on P0651 pin 1 is still approx. 12 VDC. 
-If not check Q0662. 
5.7SW B+ in SB9600 mode (high load) 
						

							 
9-16Troubleshooting 
-Connect a 68 ohm resistor from P0651 pin 1 to ground.
-Check that the DC voltage on P0651 pin 1 is still approx. 12 VDC.
-If not check Q0662. 
5.8Multiplexer in SB9600 position 
-Connect a 5.6 kohm resistor from P0651 pin 1 to ground (a keypad microphone can be used instead).
-Check that the voltage on U0655/U0656 pin 10 is 0 VDC.
-If this fails check Q0662 and Q0663. 
6Volume Control 
-Turn R0698 fully counter clockwise and then fully clockwise and verify the voltage on U0653 pin 14 goes 
from 0 V to 5 VDC.
-If not, check R0698. 
7Keypad 
-Check that when pressing a key, the correct input to U0653 pins 33-39 goes low. The actual pins can be 
found on the schematic diagram.
-Clean the carbon pads with alcohol.
-Check carbon on rubber keypad. If defect, replace keypad. 
8Key backlight 
See LCD backlight. 
9LED indicators 
-Check that the outputs from U0653 pin 49 (yellow), pin 48 (red) and pin 47 (green) changes to 5 VDC 
when LED must go ON.
-Check Q0659 (yellow), Q0660 (red) and Q0661 (green).
-Check the LEDs. 
10LCD backlight
10.1All LEDs 
If backlight cannot be turned on or off.
-Check that U0653 pins 26 and 27 are 5 VDC. If not check U0653.
-Check that the voltage of base on Q0651 is approx 1.5 VDC.
-Check Q0651 and U0652. 
						

							 
Troubleshooting9-17 
10.2One/some LEDs 
-One LED is off. Check the LED.
-One row of LEDs is off. Find the LED that makes the short circuit.  
11LCD
11.1Defect outside segments of display 
-If the LCD has either light or dark areas outside the segment, the LCD glass is defect and must be 
replaced. 
11.2Missing segments 
-Missing segments. Most likely a bad connection between PCB and LCD. Disassemble and clean PCB and 
zebra connector with alcohol. LCD glass surfaces can be cleaned with distilled water with 3% 
ammonium chloride; never use alcohol on the LCD glass.
-If necessary replace the zebra connector or LCD. 
11.3Weak segments 
-Segment brightness depends on the text displayed. Most likely a short between the lines from display 
controller/driver to LCD. Disassemble and clean PCB and zebra connector with alcohol. If necessary 
replace the zebra connector.
-Check U0651.
NOTE: When monitoring the signal on the LCD controller/driver outputs, a complex signal pattern is 
seen that jumps in 4 discrete voltage from 0V to + 5V. Waveform depends on the contents of the display. 
Outputs are never steady. A signal can always be seen on a scope unless there is a short, or the LCD driver 
is defect. 
12LCD bias voltage 
If segments that should be on are weak or segments that should be off are partly lit, the problem may be 
the bias voltage.
-Measure the LCD bias voltage (DC) between TP1 (+) and GND.
-The voltage should be approx. 5 VDC or 5.6 VDC depending on the viewing angle setting.
-Check Q0650. 
13Secure keyloading
13.1Secure keyloader sensing 
-Connect P0651 pin 2 to ground. Check that DC voltage on U0653 pin 4 goes to 0 V. If not, check P0651, 
R0679, R0678 and C0668. 
13.2Multiplexer in keyload position 
-Check that U0653 pin 42 goes to 5 VDC. If not check U0653. 
13.3Connections through multiplexer 
-Check that P0651 pins 6, 3 and 7 are connected to J0650 pins 10, 12 and 11 respectively. If not check 
U0655 and U0656.
-Also check D0683, D0684, D0685 and D0676. 
14Microprocessor U0653 
Replacement of U0653 requires special factory programming and alignment (currently not available in 
the radio service software). 
						

							 
9-18Troubleshooting 
Troubleshooting Chart 1-8B, Control Head Models II & III  
Numbers in brackets refer to accompanying troubleshooting procedure overleaf
Radio
can turn on/off?
(1.1)Check on/off switch (1.1)No
Yes
Radio
resets control
head?
(2.1)Error in radio!No
Yes Yes
5VDC
on TP3?
(1.2)Check 5V supply (1.2)No
Reset
circuit works?
(2.2)Check Q0655, U0660,
D0660 (2.2)No
Yes
Keypad
OK?
(7)Check electrical connection to µP.
Clean PCB or replace keypad (7)No
Yes Yes
Check R0697 (14) Volume
control OK?
(6)Check R0696 (6)
No
Under-
voltage detector
works?
(2.3)Replace U0660  (2.3)No
Yes
Accessory is defect!
Replace U0660  (2.3)
Micro-
processor clock
runs?
(3)Check Y0650 and U0653
(3)No
Yes
Yes
Serial bus
communication
OK? (4)Check the following:
BUS + (4.1)
BUS- (4.2)
BUSY (4.3)
BUS+/BUS- Comparator (4.4)
No
No Yes
LED
indicators
OK?Check U0654, Q0657,
Q0658, Q0659 and LEDs (9)
All LEDs?
No
Yes
Keypad
backlight
OK?
Check the LEDs
(8.2)
No
No YesYes
Check Q0650, Q0651
and Q0652 (8.1)
Yes
Communication
stops only with accessory
on MIC Conn?
(4.5)
SW B+ and
multiplexing of MIC
connector OK?
Check the following:
SW B+ voltage in normal mode (5.1)
Multiplexer in normal position (5.2)
PTT input (5.3)
Monitor input (5.4)
AUX input (5.5)
SW B+ in SB9600 Mode (5.6)
SW B+ in SB9600 Mode (high load) (5.7)
Multiplexer in SB9600 Position (5.8)
No
Text in
LCD display
OK?Check the following:
Defect outside segment area (11.1)
Missing segments? (11.2)
Weak segments? (11.3)
LCD bias voltage (8 volts)? (12)No
Yes
Secure
keyloading
OK?Check the following:
Check input from P0651 to µP U0653 (13.1)
Check multiplexer position (13.2)
Check connections through multiplexer
including ESD protection diodes (13.3)No
All LEDs?
LCD
backlight
OK?
Check the LEDs
(10.2)
No
No YesYes
Check U0654, Q0666,
Q0667 and U0656 (10.1)
Yes
Yes
Rotary
switch OK?
(14)
(model II
only)No
Replace and factory programming
and alignment necessary
Yes
Micro-
processor
OK?No
END
START
MAEPF-25122-O
FAIL 01/90
Radio never starts
after power on 
						

							 
Troubleshooting9-19 
Control Heads 
II and III Troubleshooting Procedure 
1Power Supply 
Check that the radio is connected to a power supply. 
1.1ON/OFF switch 
-Check that radio turns on. I.e. SW B+ is 12V DC. If not, press the ON/OFF switch to turn off radio.
-If the radio does not turn on, verify that there is DC voltage on the MIC-HI/ON_OFF line and that this 
voltage goes to ground when pressing the ON/OFF switch.
-If the DC voltage is present but does not go low check J0650 and R0696. 
1.25V DC supply 
-12VDC is now assumed to be present both on A+ and SW B+.
-Check that there is 5 VDC on TP3. If not check R0651 and U0650. 
2Reset 
-Check that the control head reset is functional. 
2.1Radio resets control head 
-Monitor uP reset on U0653 pin 18 with an oscilloscope. Turn radio off and on.
-Check that the uP reset goes from low to high (5 VDC) after power up and stays high. 
2.2Check reset circuit 
-If U0653 is not reset check Q0655 and U0660.
-Check that D0660 is not shorted. 
2.3Check the undervoltage detector IC U0660 
-Disconnect the control head from the radio and connect J0650 pins 7 and 13 to ground and pins 17 and 
18 to a variable DC supply.
-Measure the DC voltage at TP3.
-Monitor U0660 pin 1.
-Increase slowly the DC supply starting from 4 V.
-Check that U0660 pin 1 changes from 0V to 5 VDC when TP3 is approx. 4.3 V. If not replace U0660.
-Connect J0650 pin 3 to TP3. Check that U0660 pin 1 goes low. If not replace Q0665. 
2.4Continuous reset 
-If the control head is continuously reset by the radio it may be due to a bus communication problem or 
the microprocessor not working. 
3Microprocessor Clock 
-Check that the microprocessor oscillator is working (4 MHz square wave on TP2). If not check Y0650 and 
U0653.
-Clean PCB area round Y0650. 
4Serial Bus Communication 
A general serial bus communication problem in the radio, when the control head is connected, is 
typically indicated by an inactive radio on power up or the display showing FAIL 01/90.
Make sure no accessory is connected to P0651 (MIC Connector). Check the following lines with an 
Oscilloscope while turning the radio on and off. 
						

							 
9-20Troubleshooting 
4.1SB9600 BUS+, J650 pin 15 
-This signal is normally 5 VDC with short pulses to 0V when data are sent on the bus. If it is constantly 0 
V or 5 VDC check D0665 (most common error), Q0663 and Q0662. Check that U0653 pin 52 is 5 VDC 
with pulses to ground while sending data.
-Then check U0659 (disconnect pins 1 and 12). If problem disappears and OPTION SW B+ circuit is OK 
(see 5.), replace U0659.
-If the OPTION SW B+ circuit is defect, D0669 should also be checked. 
4.2SB9600 BUS-, J650 pin 4 
-This signal is normally 0 V with short pulses to 5 VDC when data are sent on the bus. If it is constantly 5 
VDC or 0 V, check D0664 (most common error), Q0661 and Q0662. Check that U0653 pin 52 is 5 VDC 
with pulses to ground while sending data.
-Then check U0657 (disconnect pins 1 and 12). If problem disappears and OPTION BW B+ circuit is OK 
(see 5.), replace U0657.
-If the OPTION SW B+ circuit is defect, D0667 should also be checked. 
4.3SB9600 BUSY, J650 pin 14 
-This signal is normally 0 V with pulses to 5 VDC when data are sent on the bus. If it is constantly 5 VDC, 
check D0659 (most common error) and Q0653. Check that U0653 pin 43 is 5 VDC with pulses to ground 
while sending data.
-Then check U0658 (disconnect pins 1 and 12). If problem disappears and OPTION BW B+ circuit is OK 
(see 5.), replace U0658.
-If the OPTION SW B+ circuit is defect, D0668 should also be checked. 
4.4SB9600 data in comparator 
-If the above voltages are correct, check U0656, Q0660 and Q0662.
-Finally check U0653. 
4.5Communication stops only with accessory on MIC Conn 
-If bus communication stops only when an accessory is connected to the MIC Connector (P0651), check 
the OPTION SW B+ circuit (See 5.). The accessory is either defect or incompatible. 
5OPTION SW B+/Multiplexing of MIC Connector 
Normal mode = No or simple microphone connected.
SB9600 mode = Smart accessory with serial bus connected. 
5.1SW B+ in Normal mode 
-Make sure no accessory is connected to the MIC Connector (P0651).
-With power connected to the control head on J0650 pin 17 and 18, check that the DC voltage on P0651 
pin 1 is approx. 12 VDC. If not check Q0664. 
5.2Multiplexer in normal position 
-Check that the voltage on U0657/U0658/U0659 pin 10 is 5 VDC.
-If this fails check Q0664 and Q0665. 
5.3PTT input 
-Check that the voltage on U0653 pin 9 changes from 5 VDC to approx. 1.7 VDC when P0651 pin 6 is 
connected to ground (equivalent to pressing PTT on a standard microphone).
-If this fails, check U0657. 
						

							 
Troubleshooting9-21 
5.4Monitor input 
-Check that the voltage on U0653 pin 9 changes from 5 VDC to approx. 3.3 VDC when P0651 pin 3 is 
connected to ground.
-If this fails check U0658. 
5.5AUX input 
-Check that the voltage on U0653 pin 5 changes from 5 VDC to approx. 0 VDC when P0651 pin 7 is 
connected to ground.
-If this fails check U0659. 
5.6SW B+ in SB9600 mode 
-Connect a 5.6 kohm resistor from P0651 pin 1 to ground (a keypad microphone can be used instead).
-Check that the DC voltage on P0651 pin 1 is still approx. 12 VDC.
-If not check Q0664. 
5.7SW B+ in SB9600 mode (high load) 
-Connect a 68 ohms resistor from P0651 pin 1 to ground.
-Check that the DC voltage on P0651 pin 1 is still approx. 12 VDC.
-If not check Q0664. 
5.8Multiplexer in SB9600 position 
-Connect a 5.6 kohm resistor from P0651 pin 1 to ground (a keypad microphone can be used instead).
-Check that the voltage on U0657/U0658/U0659 pin 10 is 0 VDC.
-If this fails check Q0664 and Q0665. 
6Volume Control 
-Turn R0696 fully counter clockwise and then fully clockwise and verify the voltage on U0653 pin 14 goes 
from 0 V to 5 VDC.
-If not, check R0696. 
7Keypad 
-Check that when pressing a key, both a column and a row input to U0653 pins 35-39 (rows) and 45-49 
(columns) go low. The actual pins can be found on the schematic diagram.
-Clean the carbon pads with alcohol.
-Check carbon on rubber keypad. If defect, replace keypad. 
8Keypad backlight
8.1All LEDs off or always on 
-If all keypad LEDs are OFF (or ON but never turns off), check Q0650, Q0651 and Q0652.
-The backlight ßip-ßop can be turned on by connecting the base of Q0651 through a 4k7 ohms resistor to 
5 VDC and turned off by connecting the base of Q0652 through a 4k7 ohms resistor to 5 VDC. 
8.2Light missing from some LEDS 
-Check the LEDs. 
9LED indicators 
-Check that the outputs from U0654 pin 6 (yellow), pin 9 (red) and pin 12 (green) change to 5 VDC when 
LED should go ON. 
						

							 
9-22Troubleshooting 
-Check Q0657 (yellow), Q0658 (red) and Q0659 (green).
-Check LEDs. 
10LCD backlight
10.1All LEDs 
If backlight cannot be turned on or off.
-Check that U0654 pins 16 and 19 are 5 VDC.
-If not, check U0654.
-Check that the voltage of base on Q0666 is 5 VDC.
-Check that the DC voltage of U0656 pin 1 is approx. 4.3 V.
-Check Q0667 and U0656. 
10.2One/some LEDs 
-One LED is off. Check the LED.
-One row of LEDs is off. Find the LED that makes the short circuit. 
11LCD
11.1Defect outside segments of display
-If the LCD has either light or dark areas outside the segment, the LCD glass is defect and must be 
replaced.
11.2Missing segments
-Most likely caused by a bad connection between PCB and LCD. Disassemble and clean PCB and zebra 
connector with alcohol. LCD glass surfaces can be cleaned with distilled water with 3% ammonium 
chloride; never use alcohol on the LCD glass. If necessary replace the zebra connector or LCD.
11.3Weak segments
-Segment brightness depends on the text displayed. Most likely caused by a short between the lines from 
display controller/driver to LCD. Disassemble and clean PCB and zebra connector with alcohol. If 
necessary replace the zebra connector.
-Check U0651.
-Check U0652 (model III only).
NOTE: When monitoring the signal on the LCD controller/driver outputs, a complex signal pattern is 
seen that jumps in 6 discrete voltages from -3V to + 5V. Waveform depends on the contents of the 
display. Outputs are never steady. A signal can always be seen on a scope unless there is a short, or the 
LCD controller or driver is defect.
12LCD bias voltage
If segments that should be on are weak, or segments that should be off are partly lit, the problem may be 
the bias voltage.
-Measure the LCD bias voltage (DC) between TP3 (+) and TP1 (-).
-The voltage should be approx. 8 VDC at ambient temperature.
-Check that U0654 pin 15 is high. If not check U0654.
-Check that U0655 pin 8 is approx. -5 VDC. If not check U0655.
-Check that U0653 pin 3 is approx. 2.5 VDC at ambient temperature. If not check R0742.
-Check that U0653 pin 20 is a square wave with a DC mean of approx. 3 VDC.
-If the bias regulation seems to run but the bias is too high or low this may be due to one of the following:
-1) Microprocessor has lost its factory adjustment parameters.
-2) Microprocessor is defect.
-Reprogramming of microprocessor or replacement of microprocessor requires a new factory adjustment 
currently not available in the RSS.
13Secure keyloading 
						

							Troubleshooting9-23
13.1Secure keyloader sensing
-Connect P0651 pin 2 to ground. Check that DC voltage on U0653 pin 4 goes to 0 V. If not, check P0651, 
R0690, R0691 and C0667.
13.2Multiplexer in keyload position
-Check that U0654 pin 5 goes to 5 VDC. If not check U0654.
13.3Connections through multiplexer
-Check that P0651 pins 6, 3 and 7 are connected to J0650 pins 10, 12 and 11 respectively. If not check 
U0657, U0658 and U0659.
-Also check D0666, D0661, D0667, D0668, D0669, D0721 and D0722.
14Rotary Switch (model II only)
-Turn rotary while monitoring normal radio operation.
-If rotary misses steps or jumps more than one step, replace R0697.
15Microprocessor U0653
Replacement of U0653 requires a special factory programming and alignment (currently not available in 
the RSS (radio service software). 
						

							9-24Troubleshooting
Troubleshooting Chart 1-9, Clock Distribution 
CHART 1-9   CLOCK DISTRIBUTION
No
Yes16.8MHz
on U5801-14
No
Yes2.1MHz
on U0200-E1
No
Yes3.68MHz,
or 7MHz, or 14 MHz
on U0200-D1
No
YesFrequency
on U0200-D1 divided
by 4 on 
U0103-34
Check
U0104
Check
U5800,
C5754, R5750 
Check
U5801,
R5759, C5768
Check
U0200,
R0204, L0200,
C0208, R0200 
Check
U0103
Yes
No
Frequency on
U0200-D1 on U0104-A3
and Frequency on U0200-D1
divided by 4 on
U0104-A4Check
U0103
START