Motorola Radio Mcs2000 Vol 2g 68p81080c48 O Manual

							 
Theory of Operation 13  
against over temperature conditions. The power control circuit senses 
the voltage drop across shunt resistor R3615, which is determined by 
the magnitude of the drain current in Q3561. This is a limit 
mechanism whereby the power control limits the magnitude of 
current that can be drawn by Q3561 to protect the device from 
excessive power dissipation. 
PA Power Control 
The maximum value of the PA control line is limited by R3601 and 
R3602, the resistor divider off of PA control. This inputs a signal back 
into the power control circuit that limits the magnitude of the voltage 
to which the PA control line can rise.
Reverse polarity protection for the transmitter is provided by diode 
CR3601. This diode is soldered to the board as well as being pressed 
against a member in the chassis heat sink so under reverse polarity 
conditions to the radio this diode conducts and protects the radio 
from damage. This diode also provides transient over-voltage 
protection by breaking down when the supply voltage to the radio 
exceeds 25 volts.
The power control circuit (located in the controller section of the 
radio) consists of the control amplifier (U0550-9), the control voltage 
limiter (U0202), the detector voltage buffer/amplifier (U0550-12, -13, 
-14) the PA temperature sense circuit (U0550-1, -2, -3) and the current 
limit circuit.
The voltage from the forward power detector in the PA is amplified by 
U0550-12, -13, -14. The output voltage is added to the PA power set 
voltage at the inverting input of control amplifier U0550-9. Its 
noninverting input is set to a fixed 4.65 volts. As long as there is a 
differential input voltage at the control amplifier input, the output 
voltage (PA control voltage) is altered. This in turn causes a change of 
the RF output power level and the detector voltage, which leads to a 
changing differential input voltage. When the control loop is in steady 
state the voltages at both the inverting and the noninverting input are 
equal.
To obtain a higher RF output level, the power set voltage generated by 
the D/A converter U0551-2 is reduced. This causes a lower level at the 
summing point U0550-9. The control loop compensates this 
difference by increasing RF power and detector voltage until balance 
between the two control amplifier inputs is obtained again. Reduction 
of the power level works in the opposite manner.
Operational amplifier U0202 functions as an integrator, which 
controls, via Q0556, the control voltage slope during key up and 
dekey.
During RX operation, Q0556 pulls R0590 down, the output of U0202 
is at its maximum level, Q0555 conducts and the output of U0550 is 
at its minimum output level.
After pressing PTT, transistor Q0556 switches off. Capacitor C0552 is 
charged via R0584 and R0590. In turn the output voltage of U0202 
decreases which causes an increase of the voltage at the non-inverting 
input of U550. This increases the PA control voltage. The loop is closed 
via R0591 and R0592. This feedback causes an exponential like rising 
edge of the control voltage. Such a smoothed keyup leads to an 
improved adjacent channel power reduction during TX keyup 
compared with a linear ramp. 
						

							 
14 Theory of Operation 
After keyup the circuit does not effect the performance of the power 
control circuit as long as the control voltage does not increase over a 
certain value defined by R0591/R0592 and the voltage applied to 
R0584 by the D/A output U0055-13. If this occurs the control voltage 
will be limited to the predefined value and the PA prevented from 
being damaged.
If the radio switches from TX to RX transistor Q0556 pulls R0590 
down and C0552 is discharged via R0590. This causes the output of 
U0202 to go up and tie down the noninverting input of U0550. The 
control voltage decreases controlled by the loop U0202, Q0555, and 
U0550.
The protection features in the PA power control operate by raising the 
non-inverted input to the operational amplifier above the reference 
voltage, which has the same effect as a larger input from the coupler. 
The thermal shutback circuit works when the temperature of R3610 
decreases its resistance, the output at pin 1 of U0550 increases. When 
that voltage rises above the reference voltage at pin 10 of U0550, the 
control voltage of the PA is decreased lowering the power output. The 
current limiting circuit measures the voltage drop across R3615 
causing an adjustable offset to the voltage controlled by the D to A 
output for current limit set. The difference of that is amplified at pin 7 
of U0550. When the voltage exceeds the reference at pin 10 of U0550, 
then current limit starts to engage reducing power output. 
Controller Detailed 
Functional 
Description 
The theory of operation for the controller section of the radio is 
located in Volume 1 of this service manual. 
DC Power Control 
and Regulation 
Detailed Functional 
Description 
The theory of operation for the dc power control and regulation 
section of the radio is located in Volume 1 of this service manual. 
						

							 
Reference Drawings 15 
Reference Drawings 
3 
This section contains the reference drawings listed below for the 
receiver (front end, IF, and back end), transmitter, and synthesizer 
portions of the radio.  
¥  
Overall Radio:  
-  
Transceiver Board Section Locations - Page 16  
-  
Schematic Diagram Interconnection List, Table 2 - Page 29  
¥  
Receiver:  
-  
Receiver Front End Component Locations and Parts List - 
Page 18  
-  
Receiver Front End Schematic Diagram - Page 19  
-  
Receiver IF Component Locations and Parts List - Page 20  
-  
Receiver IF Schematic Diagram - Page 21  
-  
Receiver Back End Component Locations and Parts List - 
Page 22  
-  
Receiver Back End Schematic Diagram - Page 23  
¥  
Synthesizer:  
-  
Synthesizer Component Locations and Parts List - Page 24  
-  
Synthesizer Schematic Diagram - Page 25  
¥  
Power Amplifier:  
-  
Power Amplifier Component Locations and Parts List -
Page 26  
-  
Power Amplifier Schematic Diagram -
Page 27
Refer to Volume 1 of this service manual (Motorola Publication 
68P81083C20) for reference drawings for the controller and control 
head portions of the radio.
Refer to the Secure Option service manual (Motorola Publication 
68P81083C25) for reference drawings for the secure option for the 
radio. 
Referen  
						

							 
16 Reference Drawings
Figure 2 Transceiver Board Section Locations
TRANSMITTER PA CONTROLLER
AUDIO AND POWER
REGULATION
SYNTHESIZERRECEIVER
IFRECEIVER
BACK END
RECEIVER
FRONT END CONTROLLER
COMMON
MAEPF-26504-O 
						

							 
Reference Drawings 17 
NOTES 
						

							 
18 
RESISTORS: 
R3301 0662057A97 100K
R3302 0662057A65 4700
R3303 0662057A73 10K
R3304 0662057A73 10K
R3305 0662057A18 51
R3306 0662057A73 10K
R3307 0662057A35 270
R3308 0662057A41 470
R3309 0662057A09 22
R3310 0662057A35 270
R3311 0662057C19 4.7
R3312 0662057A01 10
R3313 0662057A49 1000
R3330 0662057A61 3300
R3341 0662057A18 51
R3343 0662057A35 270
R3344 0662057A09 22
R3345 0662057A35 270 
TRANSFORMERS: 
T3301 2505515V03 4:1 BALUN
T3302 2505515V03 4:1 BALUN
T3303 2505515V07 4:1 BALUN 
Printed Circuit Board 
(For Reference Only): 
8402573Y06 
and 
8402573Y09 For Kit HUD4012D  
REFERENCE
SYMBOLMOTOROLA
PART NUMBERDESCRIPTION
REFERENCE
SYMBOLMOTOROLA
PART NUMBERDESCRIPTION
 
CAPACITORS: 
C3301 2113741F49 0.01 uF
C3302 2113741F25 1000 pF
C3303 2113740F45 56 pF
C3304 2113740F15 3.3 pF
C3306 2113740F51 100 pF
C3307 2113740F51 100 pF
C3308 2113740F51 100 pF
C3309 2113743K15 0.1 uF
C3310 2113741F25 1000 pF
C3312 2113740F51 100 pF
C3313 2113741F49 0.01 uF
C3314 2113743K15 0.1 uF
C3315 2113741F25 1000 pF
C3316 2113741F13 330 pF
C3317 2113741F13 330 pF
C3320 2113740F33 18 p F
C3321 2113740F24 7.5 pF
C3322 2113740F21 5.6 pF
C3323 2113740F18 4.3 pF
C3324 2113740F25 8.2 pF
C3325 2113740F20 5.1 pF
C3326 2113740F18 4.3 pF
C3327 2113740F22 6.2 pF
C3329 2113740F42 43 pF
C3330 2113740F45 56 pF
C3331 2113741F17 470 pF
C33322113741F17 470 pF
C3334 2113740F42 43 pF
C3336 2113740F15 3.3 pF
C3340 2113741F25 1000 pF
C3341 2113741F25 1000 pF
C3342 2113741F49 0.01 uF
C3343 2113741F49 0.01 uF
C3346 2113741F49 0.01 uF
C3348 2113741F49 0.01 uF 
DIODES: 
CR3301 4813833C02 Dual, 70V, Common 
Cathode
CR3302 4802081B58 Dual, Varicap
CR3303 4880154K03 Dual, Schottky Mixer
CR3330 4880142L01 PIN 
SHIELDS: 
E3301 2602474Y01 Preselector 
INDUCTORS: 
L3301 2462587T30 1000 nH
L3302 2462587T12 56 nH
L3304 2460591L29 16.03 nH, Airwound
L3305 2460591L29 16.03 nH, Airwound
L3306 2460591L29 16.03 nH, Airwound
L3307 2460591L29 16.03 nH, Airwound
L3308 2462587T30 1000 nH
L3309 2462587T30 1000 nH
L3320 2462587T16 120 nH
L3321 2462587T16 120 nH
L3322 2462587T16 120 nH
L3323 2462587T16 120 nH
L3325 2462587T12 56 nH
L3340 2462587T30 1000 nH 
TRANSISTORS: 
Q3301 4813824A17 PNP
Q3302 4882971R01 NPN 
RECEIVER FRONT END PARTS LIST
C3348
C3343
R3345
R3343C3341
L3325R3309
R3307
R3305C3314R3313
R3312E3301
C3304
CR3302
L3305
L3302
MAEPF-26494-O L3306
CR3303C3303
L3307L3304
C3316 L3320 C3321C3320
L3323L3321C3322
C3324
C3342C3326
C3333
C3329
C3334
C3328
C3325
L3322 C3315
R3310
C3336
L3308
C3312
R3301
C3308 C3317
C3310R3306
Q3302
C3306
C3307
C3302C3311 R3308
R3311C3323C3340
L3324
C3327
R3340
R3341C3330
C3347
C3346
R3344
T3303
T3301
T3302
HEAVY COMPONENTS SIDE
MAEPF-26495-O
C3331
R3330
C3301
C3309
R3304
C3313
Q3301
C3332
CR3330CR3301R3303R3302
L3301L3309Q3303
LIGHT COMPONENTS SIDE
 
Receiver Front End (Kit HUD4012D)
Component Locations and Parts List 
RECEIVER FRONT END COMPONENT  LOCATIONS 
NOTES:
1. All resistance values are in ohms unless indicated otherwise.
2. Components shown on component location and schematic 
diagrams but not included in parts list are not placed. 
 
This document was created with FrameMaker 4.0.3 
						

							 
19
 
9.3V
N.U.
IF_IN
(TO RECEIVER IF)
RX INJREG 5V 9.3V
IF4-4-2
E3301
63A81090C56-O
 
Receiver Front End (Kit HUD4012D) Schematic Diagram  
 
This document was created with FrameMaker 4.0.3 
10_RFE SD p19  Page 19  Tuesday, January 19, 1999  4:57 PM 
						

							 
20 
FILTERS: 
Y3401 4805846W01 Crystal, 44.85 MHz 
Y3402 4805846W03 Crystal, 44.85 MHz 
PRINTED CIRCUIT 
BOARD (For
Reference Only): 
8402573Y06 
and 
8402573Y09 For Kit HUD4012D  
REFERENCE
SYMBOLMOTOROLA
PART NUMBERDESCRIPTION
C3402R3410
CR3402
L3407
R3412 C3418
C3411 C3417 C3414
C3416
R3409
C3409
L3406C3419 R3403
MAEPF-26496-O L3402
Y3401
Y3402
L3401
C3401
R3401
C3335
R3404
C3407 C3403
L3403
R3408 R3405
R3414R3413
R3406
R3402
C3415
R3415
CR3401
C3408 C3410
C3412L3404C3404
C3405
R3411C3413 C3406
Q3401
MAEPF-26497-O C3361
C3305C3351
L3340 C3364 L3351L3350
C3420
C3360
Q3402
C3350
C3363
C3352
C3353
C3354
C3357
C3358C3355C3359
 
Receiver IF (Kit HUD4012D)
Component Locations and Parts List 
RECEIVER IF COMPONENT LOCATIONS 
REFERENCE
SYMBOLMOTOROLA
PART NUMBERDESCRIPTION 
CAPACITORS: 
C3305 2113741F49 0.01 uF
C3335 2113740F18 4.3 pF
C3350 2113740F51 100 pF
C3351 2113740F51 100 pF
C3352 2113740F51 100 pF
C3353 2113740F51 100 pF
C3355 2113740F51 100 pF
C3357 2113740F51 100 pF
C3358 2113741F58 100 pF
C3359 2113741F49 0.01 uF
C3360 2113740F51 100 pF
C3361 2113740F51 100 pF
C3401 2113740F24 7.5 pF
C3402 2113740F25 8.2 pF
C3403 2113740F31 15 pF
C3404 2113743A19 0.1 uF
C3405 2113740F24 7.5 pF
C3406 2113741F49 0.01 uF
C3407 2113740F51 100 pF
C3408 2113741F49 0.01 uF
C3409 2113741F49 0.01 uF
C3410 2113740F15 3.3 pF
C3411 2113741F13 330 pF
C3412 2113740F25 8.2 pF
C3413 2113741F25 1000 pF
C3414 2113740F09 1.8 pF
C3415 2113740F09 1.8 pF
C3416 2113740F27 10 pF
C3417 2113740F45 56 pF
C3418 2113740F31 15 pF
C3419 2113740F44 51 pF 
DIODES: 
CR3401 4880142L01 PIN
CR3402 4880154K03 Dual Schottky Mixer 
INDUCTORS: 
L3401 2462587T30 1000 nH
L3402 2462587T30 1000 nH
L3403 2462587T30 1000 nH
L3404 2462587T30 1000 nH
L3406 2462587T30 1000 nH
L3407 2462587T30 1000 nH 
TRANSISTORS: 
Q3303 5105625U28 Mixer, Integrated Circuit
Q3401 4882022N70 NPN 
       
RESISTORS: 
R3401 0662057A18 51
R3402 0662057A18 51
R3403 0662057A73 10K
R3404 0662057A73 10K
R3405 0662057A35 270
R3406 0662057A39  390
R3408 0662057A01 10
R3409 0662057A49 1000
R3410 0662057A59 2700
R3411 0662057A41 470
R3412 0662057A53 1500
R3413 0662057A39 390
R3414 0662057A01 10
R3415 0662057A73 10K 
RECEIVER IF PARTS LIST 
NOTES:
1. All resistance values are in ohms unless indicated otherwise.
2. Components shown on component location and schematic 
diagrams but not included in parts list are not placed. 
HEAVY COMPONENTS SIDE
LIGHT COMPONENTS SIDE 
 
This document was created with FrameMaker 4.0.3 
11_RIF CL/PL p20  Page 20  Tuesday, January 19, 1999  4:58 PM 
						

							 
21
N.U.
N.U.
N.U.
N.U.9.3V 9.3V
9.3V
N.U.N.U.47k47k
IF_IN
(FROM RECEIVER
FRONT END)
63A81090C57-O
N.U.
 
Receiver IF (Kit HUD4012D)Schematic Diagram  
 
This document was created with FrameMaker 4.0.3 
						

							 
22 
REFERENCE
SYMBOLMOTOROLA
PART NUMBERDESCRIPTION 
  
CAPACITORS: 
C3201 2113743K15 0.1 uF
C3202 2113740F51 100 pF
C3203 2113743K15 0.1 uF
C3204 2113743A23 0.22 uF
C3205 2113743K15 0.1 uF
C3206 2113743K15 0.1 uF
C3207 2113743A23 0.22 uF
C3208 2113743K15 0.1uF
C3209 2113743K15 0.1uF
C3210 2113740F41 39 pF
C3211 2113743A19 0.1uF 
C3212 2113743A23 0.22uF
C3213 2113743A23 0.22uF
C3214 2113741A51 0.018 uF
C3215 2311049A02 0.15 uF
C3216 2113743K15 0.1 uF
C3217 2113740F37 27 pF
C3218 2113740F41 39 pF
C3219 2113740F42 43 pF
C3220 2109720D14 0.1 uF
C3221 2113741F17 470 pF
C3222 2109720D14 0.1 uF
C3223 2113743K15 0.1 uF
C3224 2113743K15 0.1 uF
C3225 2113743K15 0.1 uF
C3229 2311049J23 10 uF
C3230 2113743K15 0.1uF
C3231 2113741F25 1000 pF
C3232 2113743K15 0.1uF
C3234 2113740F19 4.7 pF
C3243 2113743K15 0.1uF
C3245 2113743K15 0.1uF
C3246 2113743K15 0.1uF
C3247 2113741F49 0.01 uF
C3249 2113740F15 3.3 pF
C3250 2113740F22 6.2 pF 
DIODES: 
CR3201 4862824C01 Varactor
CR3203 4805129M96 Dual
CR3204 4880154K03 Dual Schottky Mixer 
SHIELD: 
E3201 2605261V01 ZIF 
INDUCTORS: 
L3204 2462587T23 470 nH
L3205 2462587Q44 560 nH
L3207 2462587T23 470 nH
L3208 2462587T30 1000 nH 
TRANSISTORS: 
Q3201 4882022N70 NPN
Q3203 4882022N70 NPN 
RECEIVER BACK END PARTS LIST 
RESISTORS: 
R3201 0662057A89 47K
R3202 0662057A89 47K
R3203 0662057A80 20K
R3204 0662057A59 2.7K
R3205 0662057A59 2.7K
R3206 0662057A59 2.7K
R3209 0662057A53 1.5K
R3210 0662057B47 0
R3211 0662057A84 30K
R3212 0662057A73 10K
R3215 0662057B05 200K
R3216 0662057A42 510
R3217 0662057A53 1.5K
R3218 0662057A53 1.5K
R3219 0662057A65 4.7K
R3220 0662057A81 22K
R3221 0662057A53 1.5K
R3222 0662057A73 10K
R3223 0662057A77 15K 
INTEGRATED CIRCUITS: 
U3201 5186296A02 Zero IF, F91 P-3 
PRINTED CIRCUIT 
BOARD (For
Reference Only): 
8402573Y06 
and 
8402573Y09
For KIt HUD4012D
 
REFERENCE
SYMBOLMOTOROLA
PART NUMBERDESCRIPTION
C3247
C3249
C3250
R3219 R3220 C3248
R3205
R3206C3234
C3218
L3204
C3231 C3225 R3223 R3210
R3212 R3211
Q3203L3207
CR3203E3201
R3201
R3202C3217
MAEPF-26498-O C3210
C3229
C3232
Q3201
C3219R3203
CR3201
R3221
R3209
C3243
R3222 C3203
CR3202C3246 L3208
MAEPF-26499-O
U3201
R3224 C3216
C3222
R3215
C3221
C3220
C3213
C3212
C3207
C3245C3211R3217 C3230 C3205C3201
C3202L3205
R3216
R3218
C3224
C3204
C3208
C3209
C3206CR3204C3223 C3214
R3204 C3215
 
Receiver Back End (Kit HUD4012D)
Component Locations and Parts List 
RECEIVER BACK END COMPONENT LOCATIONS 
HEAVY
COMPONENTS
SIDE
LIGHT
COMPONENTS
SIDE
 
NOTES:
1. All resistance values are in ohms unless indicated otherwise.
2. Components shown on component location and schematic 
diagrams but not included in parts list are not placed. 
 
This document was created with FrameMaker 4.0.3 
13_RBE CL/PL p22  Page 22  Tuesday, January 19, 1999  5:03 PM