Midland 70-050 User manual

iilDLAND ©VINl^rHOlH]
VHF (LOW BAND)
SERVICE MANUAL
70-050
70-055
1690 North Topping Avenue
Kansas City, Missouri 64120 70-300500
09-050055-SM-3/85-1M

70-050/055
The Midland Models 70-050A, 70-050B, 7 0 - 0 5 ° C ’
7n D55C are solid state VHF Low Band Land Mobile
“ opera e the 29-37 MHz (7O-05OA, 70-055A)
70-053b 5 and 40-54 MHz (70-050C, 70-0550 ranges
70-05 5A, 70-055B, and
transceivers designed
35_44 MHz (70-050B,
and field
programmable/
these S'YN-TECH
Providino up to 80 channel capability
rroviu-Lug f r . 1P n r ies and options,
models^are^esignet/lc/providt^flexible c.Snlc.t* on. .or a vartet,
of applications.
distributed in the following forms.
service
; h e d and
Manual Addition (MA)
Change
Notice (CN)
Provides additional information useful
in unit alignment and service or to
upgrade for increased capability,. rrm
ted on BLUE paper.
rcuitry changes made during
by model and serial number.
YELLOW paper.
Details
production
Printed on
Manual Correction (MC)
Corrects manual errorsnot related to
production changes. Printed on
paper.
— , . . nii t i n (TB)- Provides solutions for field problems
fechmcal Bulletin ( ) ^ Lips for performance improvement.
. n T 11 1/ _ „ ~ ~
Careful use of
installed and
areas of manual
the manual information wilJ
maintained units. Comments
improvement are welcome.
insure properly aligned,
or suggestions conceining

TABLE OF CONTENTS
70-050/055
INTRODUCTION . P a 8 e 2
TABLE OF CONTENTS . p age 3
SPECIFICATIONS
General.P a 8 e 4
Receiver Performance.page 5
Transmitter Performance and CTCSS . page 6
E/PROM PROGRAMMING . p ages 7,8,9
THEORY OF OPERATION . pages 10,11,12,13,14
BLOCK DIAGRAM . P a 8 e 15
SUGGESTED TEST INSTRUMENTS . p age 16
Test Equipment Set-Up Diagrams.page 16
ALIGNMENT INSTRUCTIONS . p ages 17,18
Receiver & PA Board Alignment Points Diagram.page 19
Transmitter Alignment Points Diagram.page 20
Supplemental Alignment Instructions.page 21
PC BOARDS
E/Prom (Top & Bottom), Display CX-03 (Top & Bottom).page 22
Control CX-04, Control Interface CX-05 (Top 6 Bottom).page 23
Display Driver CX-06 (Top & Bottom)...page 23
Display CX-07 (Top & Bottom), Control Cable CX-08.page 24
CONTROL HEAD SCHEMATIC DIAGRAM 70-055A,B,C . p age 25
CONTROL INTERFACE SCHEMATIC DIAGRAM 70-055A.B.C . p age 26
CONTROL PANEL SCHEMATIC DIAGRAM 70-050A,B,C . p age 27
PC BOARD INTER-CONNECT DIAGRAMS
70-050A/B/C.P a S e 28
70-055A/B/C.Page 29
RECEIVER PC BOARD DRAWINGS
70-050/055 (Top View).page 31
70-050/055 (Bottom View).page 32
RECEIVER SCHEMATIC DIAGRAMS
70-050A/B/C.page 33
70-055A/B/C.. 34
TRANSMITTER PC BOARD DRAWINGS
70-050/055 (Top View). P age 35
70-050/055 (Bottom View).page 36
PA PC BOARD DRAWINGS
70-050/055 (Top View).page 37
70-050/055 (Bottom View).page 38
TRANSMITTER SCHEMATIC DIAGRAM . p age 39
VOLTAGE CHARTS
Transistors.page 40
Transistors, F.E.T.'S, Digital IC.page 40
Analog IC 6, IC901 Pin Out.page 41
SIMPLIFIED SQUELCH CIRCUIT SCHEMATIC . p age 42
REPAIR INFORMATION
Chip Component Identification Removal, Replacement.page 43
IC Removal, Replacement.page 44
PC Board Removal.page 45
TROUBLE SHOOTING CHARTS
General .
Receiver.
Transmitter, Modulator.
CPU/PLL . .
MOBILE INSTALLATION DIAGRAMS
70-050..
70-055.
INSTALLATION INSTRUCTIONS .
NOISE SUPPRESSION .
ACCESSORIES .
UNDER DASH DC POWER/ACCESSORY PLUG INSTRUCTIONS .
TRUNK MOUNT DC POWER/ACCESSORY PLUG INSTRUCTIONS .
MICROPHONE HANG-UP BOX & PARTS LIST .
MICROPHONE SCHEMATIC & PARTS LIST .
EXPLODED MECHANICAL VIEW DRAWINGS
70-050.
70-055.
PARTS LIST . p ages
PARTS ORDERING INFORMATION .
APPENDIX - OPTION INFORMATION
CTCSS Board, Model 70-2102A .
2/2.5 PPM Oscillator Kits, Models 70-2124/2125.
12.5 KHz Channel Spacing Kit, Model 70-2132 . .
Scan Kit (UD), Model 70-2141.
Scan Kit (TM), Model 70-2142.
Two Tone Sequential Decoder, Models 70-2151/2152
Noise Blanker Kit, Model 70-2191.
Tone Enabled Transmit/Receive .
Base Station Mic Adaptor Kit, Model 70-K33. . .
Special Busy Channel Lock-Out .
.page 47
.page 48
.page 49
.page 50
.page 51
.page 52
.pages 53,54
.pages 55,56
.page 57
.page 58
.page 59
.page 60
.page 61
.page 63
.page 64
65,66,67,68,69,70,71,72,73,74,75,76
.page 77
. . .pages 79,80,81,82,83,84,85,86
.page 87
.pages 88,89
.page 90
.page 91
.pages 92 thru 102
.pages 103,104
. page 105
. page 106
.pages 107,108
3

GENERAL SPECIFICATIONS 70-050/055
Nominal operating voltage:
Temperature range:
Antenna impedance:
Microphone:
Speaker - internal:(70-050A/050B/050C)
external:
Frequency control:
Frequencies of operation:
Receiver and transmitter performance
bandwidth without adjustment:
Maximum transmit-to-receive
frequency separation:
Frequency tolerance and stability:
Duty cycle:
High humidity:
Vibration stability:
Shock stability:
Channel capability:
Current drain - Standby:
Receive:
Transmit:
Dimensions (HWD):
Main chassis: (70-050/055)
Control head: (70-055)
Speaker: (70-055)
Weight:
Main chassis: (70-050/055)
Control Head: (70-055)
Speaker: (70-055)
13.6V DC (negative ground)
(12.2-16V DC range)
-30°C to +60°C
50 ohms, unbalanced
Dynamic element, with amplifier
8 ohms
4 ohms
Frequency synthesized with
EPROM Programming
29-37 MHz (70-050A/055A)
35-44 MHz (70-050B/055B)
40-54 MHz (70-050C/055C)
1.0 MHz Standard
2.0 MHz (Optional)
2.0 MHz
+5 PPM Tx and Rx (Standard)
+2.5 or 2.0 PPM Tx and Rx (Optional)
Intermittent EIA RS 152-B
(1 minute Tx, 4 minutes Rx)
95% @ 50°C per EIA
RS-152-B, sec. 13
EIA RS-152-B, sec. 14
EIA RS-152-B, sec. 15
Up to 80 channel transmit/receive
0.35 A DC
1.00 A DC
8.00 A DC
65 x 185 x 280mm (2% M x 7V x 11")
50 x 88 x 80mm (2" x 3%" x 3 3/16")
100 x 100 x 77mm (4" x 4" x 3")
3.0 kg (6.6 lb.)
0.8 kg (1.8 lb.)
0.71 kg (1.58 lb.)
4

RECEIVER SPECIFICATIONS
70-050/055
Refer to EIA RS-204-C and
Standard of Performance.
Sensitivity:
Squelch sensitivity:
DOC RSS-119 for Method of
12dB SINAD
Threshold
Tight
Measurement and
0.25uV @50 ohm
0.2uV max or 6dB
SINAD
1.OuV min, 2.OuV max
Squelch blocking:
Receiver attack (squelch release)
time:
Receiver squelch closing time:
Modulation acceptance bandwidth:
lOdB
100ms max
200ms max
+7.0KHz min @ 20/25/30 KHz
+4.5KHz min @ 12.5 KHz
Adjacent channel two signal
selectivity and desensitization:
Spurious response attenuation:
Intermodulation spurious response
attenuation:
(measured at useable sensitivity)
Audio power output:
Audio frequency response:
Hum and noise:
Conducted suprious RF power:
90dB @ +20KHz
90dB
80dB (Noise Blanker off)
75dB (Noise Blanker on)
1W @ 5°6 THD @ 8 ohms (Internal)
5W a 5°o TI1D @ 3.2 ohms (External)
Per EIA and DOC Specifications
Unsquelched 40dB
Squelched 50dB
200uV across 50 ohms (800pW)
from DC to 1000MHz
Intermediate Frequencies: 10.7MHz (1st) and 455KHz (2nd)
SCAN SPECIFICATIONS
Scan speed: 20 channels/second
Channel capacity: 64 (PRI)
64 (SCAN)
Scan detection:
Scan resume delay:
Carrier, tone or vacant channel
0.3, 2.5/5 seconds or infinite
5

TRANSMITTER SPECIFICATIONS
70-050/055
Refer to EIA RS-152-B and DOC RSS-119 for Method of Measurement and
Standard of Performance.
Carrier power output:
Modulation system:
Audio frequency response:
Audio frequency harmonic
distortion:
System deviation:
Modulation limiting:
Hum and noise:
Occupied bandwidth:
Transmitter carrier attack time
Conducted spurious emissions:
Microphone input level and
impedance:
50W minimum, adjustable 25-50W
(optional 1-50W)
PM .
Per EIA and DOC RSS-119
Specifications
3% @ 1000Hz for +3.OKHz deviation
+5KHz, max
Instantaneous peak clipping with
low pass audio filter
50dB
Less than 25uW adjacent channel
power, +30KHz (-60dB from carrier
power)
100ms max for 50% rated power
Less than 25uW, 1MHz to 1000MHz
-8dbm +3dB/600 ohms
Output protection: Shall withstand for 5 minutes all VSWR around
Smith Chart of 20:1 without failure or damage.
Output stability:
Shall not exceed spurious emission requirements
when operated into a mis-match load with 5:1 VSWR
at any point on the Smith Chart.
CTCSS SPECIFICATIONS
(Optional, not supplied with unit)
Code Frequencies:
Modulation limits:
Decode sensitivity:
Receiver response time:
Encoder Response time:
Transmitter tone distortion:
Transmitter intermodulation
distortion:
SPECIFICATIONS SUBJECT TO
All EIA Standard from 67Hz to 241.8Hz
500 - 1000Hz
Less than 5dB SINAD
200ms max
50ms max
5% max
10 %
CHANGE WITHOUT NOTICE
6

E/PROM PROGRAMMING
70-050/055
E/PROM MODULE LOCATION AND REMOVAL
The operating frequencies and optional functions for the Midland 70—
050/055 transceivers are programmed in a semiconductor-memory E/PR0M
module. To remove the module for programming, first remove the trans¬
ceiver top cover, then locate the small printed circuit board near the
front of the unit, marked "Z-273". The module is mounted on two
connectors and can be separated from the main printed circuit board by
simply pulling straight up.
PROGRAMMING PREPARATION
NOTE: The 70-050/055 contains the HD44840A22 or
HD44840A27 microcomputer (IC 9 01). The 70-1C00
programmer used to program E/PR0M modules for the
70-050/055 must be upgraded to the "E0" or later
configuration.
The 70-1000 E/PR0M Programmer Operator’s Manual contains detailed
information concerning E/PR0M module programming. Be careful to
observe the following precautions.
DO NOT APPLY OR REMOVE PROGRAMMER AC POWER WHILE THE
E/PR0M MODULE IS PLUGGED INTO THE PROGRAMMER.
IT IS NOT NECESSARY OR RECOMMENDED TO PLUG THE E/PR0M
MODULE INTO THE PROGRAMMER EXCEPT TO PERFORM BLANK
CHECK, WRITE, VERIFY OR COPY OPERATIONS.
Apply power to the 70-1000 programmer and confirm the correct display
is present.
HEADING INPUT
Input the optional heading data as described in the 70-1000 manual.
BAND SELECTION
A band selection code must be entered to program the frequency range,
IF and reference frequencies, and local oscillator injection. he
standard configuration 70-050/055 will accept only Band 50, which is
entered as BAND CODE 0. Band 50 corresponds to a 30-50MHz frequency
range, 10.7 MHz RX IF, 10.24 MHz TX IF, 5 KHz reference frequency and
high side local oscillator injection.
The 70-050/055 can be converted to accept bands 5A, 5B, 5C, 5D or 5E
as follows:
1. Band 5A, BAND CODE 0A, differs from Band 50 only in using low side
receiver local oscillator injection instead of high side. Low side
injection may be used to reduce or eliminate interferenie from
intermodulation products. Band 5A should be programmed only if the Low
Side Injection Kit 70-2175 (70-050A/055A), 70-2176 (70-050B/055B) or
70-2177 (70-050C/055C) has been installed in the radio. If a Low Side
Injection Kit has been installed. Band 50 cannot be used.
7

E/PROM PROGRAMMING
70-050/055
2. Band 5B utilizes a 9.6 MHz TX IF, 12.5 KHz reference frequency and
high side local oscillator injection. This band selection allows the
programming of "splinter" frequencies at 12.5 KHz channel spacings.
The 70-2132 12.5 KHz Channel Spacing Kit must be added to the radio to
allow operation on these frequencies. Only those frequencies which are
evenly divisible by 12.5 KHz may be programmed in Band 5B. If full
specification receiver performance is required on adjacent 12.5 KHz
spaced channels, the 12.5 KHz 1st. / 2nd IF Filter Kit 70-2135 should
also be added to the transceiver.
3. Band 5C allows the programming of "splinter" frequencies with low
side local oscillator injection instead of high side. To utilize this
band, both the 70-2132 12.5 KHz Channel Spacing Kit and the
appropriate 70—2175/2176/2177 Low Side Injection Kit must be installed
in the radio. Other band selection codes may not be used after this
conversion .
4. Band 5D, BAND CODE 0D, utilizes a 10.24 MHz TX IF, 2.5 KHz
reference frequency and high side local oscillator injection. This
band selection allows mixed programming of standard 15 KHz spaced
channels and 12.5 KHz "splinter" frequencies. To utilize this band,
the 70-2138 2.5 KHz Channel Spacing Kit must be installled.
NOTE: Radios containing the 70-2138 kit can be programmed on_l.X with
programmers configured with "0.0" and later software.
5. Band 5E, BAND CODE 0E, allows the mixed programming of standard 15
KHz spaced channels and 12.5 KHz "splinter" frequencies with low side
local oscillator injection instead of high side. The 70-2138 kit and
the appropriate low side injection kit must, be installed in the radio.
CHANNEL PROGRAMMING
When the band selection has been, channel frequencies and auxiliary
codes can be entered as outlined in the 70-1000 Operator s Manual.
Note that. Auxiliary Code "0" (tone disable) is automatically
programmed for each transmit and receive channel if no other code is
entered. Auxiliary data may be programmed in E/PROM even if the CTCSS
option is not installed in the transceiver.
If the transceiver installation causes all power to be removed from
the unit by the ignition switch, it. should be noted that, the powerup
channel will always by the lowest numbered channel programmed. As long
as power is supplied to the radio power/auxiliary connecter, the
channel, in use at unit, turn-off will be displayed at. turn-on.
SCAN PROGRAMMING
Up to 64 channels can be programmed in each of 2 scan groups. Refer to
the 70-1000 Operator's Manual for programming details.
FUNCTION CODE PROGRAMMING
Eight transceiver functions are programmable by function code inputs
8

E/PROM PROGRAMMING
70-050/055
as detailed in the 70-1000 Operator's Manual.
The Busy Channel Lockout function, if programmed, prevents inadvertent
transmission on a occupied frequency and can be programmed to audibly
warn the operator that, transmission is not occuring. The BCL0 function
can be jumper selected to operate on carrier or CTCSS tone. The
standard radio is configured for carrier BCL0 by JP107. If tone BCL0
is desired, remove JP107 and install a jumper in the JP108 position.
DO NOT operate the radio with both JP107 and JP108 installed. Time Out
Timer programming is selectable from 30 seconds to 210 seconds as
detailed in the 70-1000 manual.
Note that for all radios programmed for either noise squelch scan or
CTCSS scan, the automatic default condition should be used for
function codes 3 and 4 (intervals A and B). These same default
conditions should also by used if no scan channels are programmed.
PROGRAMMING THE E/PROM MODULE
Carefully check the programming data entered in the buffer RAM of the
programmer for correctness by repeatedly pressing ENTER or by printing
out the buffer RAM contents on the 70-1300 printer.
Prepare the E/PR0M module for programming by a thorough erasure in the
70-1100 E/PROM Eraser. Plug the E/PR0M module in the programmer
adapter, noting the following precaution.
MAKE SURE THE E/PR0M MODULE CONNECTORS MATE PROPERLY WITH THE
ADAPTER PINS AND ARE NOT OFFSET IN EITHER DIRECTION.
Remove the module at the completion of the Blank Check, Write and
Verify operations. Reinstall the E/PR0M module in the transceiver,
again checking for proper mating of the connectors.
9

THEORY OF OPERATION
0-0
PLL/Synthesizer Function
The frequency synthesizer consists of two phase-locked loops. One loop
(Main PLL) is controlled directly by the microcomputer and generates
the receive local oscillator frequency. This loop also generates a
frequency used in the second loop (Transmit PLL) for transmitter
operat ion .
Reference Oscillator and Main PLL
A stable frequency for the entire radio is generated by a crystal
oscillator composed of X101, Q701 and related components. This
oscillator operates at 5.12 MHz and stability is maintained by use of
a posistor crystal heater. This 5.12 MHz signal is divided by 1024 in
IC701 to give the 5kHz reference frequency for the Main PLL loop
consisting of IC701 (phase comparator and programmable divider), Q704-
706 (loop low pass filter), D702/707 (VCO), and IC703 (pre-scaler).
The VCO frequency is equal to the channel frequency plus 10.7 MHz in
receive and channel frequency plus 10.24 Mhz in transmit. The VCO
frequency is divided by 32/33 by pre — scaler IC703 and further divided
in IC701. The division ratio of IC701 is controlled by the 8 bit code
latched into the shift register IC902 from the E/PR0M IC951 under
control of the microcomputer IC901 . The 8 bit code is sent in serial
fashion from IC902 to 1C701 under microcomputer control. Besides being
a programmable divider, IC701 is also a phase comparator which gene¬
rates an error signal for VCO control if the programmable divider
output, is out of phase with the 5 KHz reference frequency.
Modulator and Transmit PLL
The 5.12 MHz oscillator output is also fed to IC702 where it is
divided by 8 to give 640 KHz. This signal goes directly to the trans¬
mit phase shift modulator D101/D102. Audio from the microphone is
shaped and limited by IC101 (instantaneous deviation control),, fil¬
tered and buffered and fed to the phase shift modulator. The modulator
output becomes the reference frequency for the Transmit PLL loop
consisting of IC103 (phase comparator), D104/Q108 (VCO), D108 (mixer),
and 1C106 (fixed divider). The VCO output, is at the transmit channel
frequency and is mixed at D108 with the Ftx + 10.24 MHz signa.. from
the Main PLL loop to yield 10.24 MHz. This frequency is divided by 16
at 1C106 to give 640 KHz and compared with the 640 KHz reference
signal from the modulator. Thus the VCO output is forced to track the
modulated reference signal, reproducing this modulation at the trans¬
mit frequency. 1C102 detects any large differences between the two
phase comparator inputs and generates an out-of-lock signal which
biases Q111 on and prevents any transmitter signal from reaching the
power amplifier stages. Q111 is also biased on during receive by a
signal from the microcomputer IC901 pin 6.
Transmit Power Amplifier and APC (Automatic Power Controller)
The transmit PLL output, is amplified by Q1 10 before being fed : o the
PA section. The (1110 output is amplified to rated output by Q501 (pre¬
driver), Q502 (driver), and the final transistor Q503. A sample of the
RF output is detected by D501 and coupled to the diffential amplifier
10