Tait TM8110 Service Manual

TM8100/TM8200 Service Manual Transmitter Fault Finding (25W) 341
© Tait Electronics Limited June 2006
Task 11 —
Power and Current
Are Low
If the RF output power and the supply current are uniformly low at all
frequencies, one of the PAs is suspect or the input to the PAs is reduced.
Check each PA in turn:
1. For the first PA (Q310), enter the CCTM command 331 to check the
DAC value of final bias 1 (
CDC TX FIN BIAS 1). Record the value x
returned.
2. Note the current reading on the DC power supply.
3. Enter the CCTM command 331 1 to turn off final bias 1.
4. Enter the CCTM command 33 to place the radio in transmit mode.
5. Note the RF output power measured at the test set. This should be
as shown in Table 12.5.
6. If the RF power is correct, go to Step 7 to repeat the check with the
second PA. If it is not, enter the CCTM command 32 to place the
radio in receive mode, and carry out Task 12
and then Ta s k 1 3.
7. For the second PA (Q309), enter the CCTM command 332 to check
the DAC value of final bias 2 (
CDC TX FIN BIAS 2). Record the value y
returned.
8. Note the current reading on the DC power supply.
9. Enter the CCTM command 332 1 to turn off final bias 2.
10. With the radio still in transmit mode, note the RF output power
measured at the test set. This should be as shown in Table 12.5.
11. Enter the CCTM command 32 to place the radio in receive mode.
12. If the RF power measured in Step 10 is correct, go to “RF Signal
Path” on page 361. If it is not, carry out Tas k 12
and then Ta s k 1 6.
Table 12.5 RF output power of individual RF power amplifiers at different frequencies
Frequency band
Frequency within band
Lowest frequency Centre frequency Highest frequency
A4 24 ± 5W 25 ± 5W 25 ± 5W
B1 29 ± 5W 34 ± 5W 29 ± 5W
C0 23 ± 5W 22 ± 5W 17 ± 5W
D1 33 ± 5 W 28 ± 5 W 29 ± 5 W
H5 5 ± 5W 12 ± 5W 27 ± 5W
H6 13 ± 5W 19 ± 5W 28 ± 5W

Tait TM8110 Specifications

General

IP Rating	IP54
Channel Spacing	12.5 kHz / 25 kHz
Modulation	FM
Operating Temperature	-30°C to +60°C
Frequency Range	136-174 MHz, 403-470 MHz, 450-520 MHz

Summary

Chapter 1: Description of the Radio

1 Introduction

Overview of the TM8100 and TM8200 series radios, covering frequency bands, RF output power, accessories, and product codes.

1.1 Frequency Bands

Details the available frequency bands for the radios, such as A4, B1, C0, D1, H5, H6, and H7.

1.2 RF Output Power

Describes the two RF output power options available: 40W/50W and 25W.

1.3 Accessories

Lists various audio accessories, installation kits, internal options boards, and other accessories for the radios.

1.4 Product Codes

Explains the product codes used to identify TM8100 and TM8200 mobile radio products and their features.

Chapter 2: Servicing the Radio

4 General Information

Discusses repair levels, website access, tools, equipment, spares, test equipment setup, and servicing precautions.

4.1 Repair Levels and Website Access

Details the manual's coverage of level-1 and level-2 repairs and outlines website access levels for technical information.

4.3 Servicing Precautions

Covers essential precautions for servicing radios, including mechanical, compliance, anti-static, and transmitter issues.

5 Disassembly and Reassembly

Provides instructions on how to remove and mount the control head, and disassemble/reassemble the radio body and control heads.

Chapter 9: Frequency Synthesizer Fault Finding

9.1 Initial Checks

Describes two types of initial checks: calibration checks and lock status, depending on fault symptoms.

9.2 Power Supplies

Details the four power supplies for the frequency synthesizer and measurement points for diagnosing faults.

9.3 Phase-locked Loop

Explains checking critical PLL outputs and inputs, including charge pump supply and reference frequency.

9.4 Loop Filter

Guides on checking loop filter functionality by measuring loop voltage, VCO fault, reference voltage, and feedback voltage.

Chapter 10: Receiver Fault Finding

10.1 Faulty Receiver Sensitivity

Covers determining the extent of receiver sensitivity loss and checking receiver gain.

10.2 Excessive Loss of Sensitivity

Details fault diagnosis for excessive receiver sensitivity loss, covering power supplies, logic signals, lock status, IF amplifier biasing, and matching circuitry.

10.4 Incorrect RSSI Readings

Addresses issues with incorrect RSSI readings, focusing on AGC voltage calibration and RSSI delta gain.

Chapter 11: Transmitter Fault Finding (40W/50W)

11.1 Power Supplies

Checks the two power supplies and the switch circuit for the transmitter, including 13.8V DC and 9V DC supplies.

11.2 Transmitter RF Power

Guides on checking transmitter RF power, including forward/reverse powers and output power, and troubleshooting based on results.

11.3 Biasing of PA Driver and PAs

Details checking and repairing biasing for Power Amplifiers (PAs) and the PA driver, including DAC values and current readings.

Chapter 13: CODEC and Audio Fault Finding

13.1 Power Supplies

Checks the 9V, 3V, and 2.5V DC supplies for the CODEC and audio circuitry.

13.2 Faulty Speaker Audio

Covers diagnosing faults related to no speaker audio or distorted speaker audio, checking audio power amplifier and speaker outputs.

13.4 Faulty Receiver

Addresses issues where the receiver does not operate, checking level shifter and QN test point.

Chapter 14: Fault Finding of Control Head with Graphical Display

14.1 CCTM Commands

Lists CCTM commands used for fault finding of the control head, including LED, LCD, and key functions.

14.2 Power Supply Faulty

Guides on checking 3.3V and 13.8V supply voltages to the control head and its components.

14.3 LCD Display Faulty

Provides steps for troubleshooting a faulty LCD display, including checking connections, contacts, and replacing the LCD.

14.4 LCD Backlighting Faulty

Covers troubleshooting LCD backlighting issues, including checking supply voltage, signals, and components like Q102.

Chapter 15: Fault Finding of Control Head with 1- 2- or 3-Digit Display

15.1 Display Faulty but not LEDs

Focuses on diagnosing faults where the display functions partially or not at all, checking elastomeric strips and LCD.

15.3 All LEDs Faulty

Outlines procedures for when all LEDs are faulty, including checking IC3 and replacing the control-head board.

15.5 Some but not All Keys Faulty

Details troubleshooting steps for individual or groups of faulty keys on the control head.

Chapter 16: Spare Parts

16.1 Radio Body

Lists serviceable parts for the radio body, including cover, lid, chassis, and connectors, with IPNs and quantities.

16.2 Control Head with Graphical Display

Lists serviceable parts for the graphical display control head, including screws, loom, keypad, and LCD assembly.

16.3 Control Heads with 1-, 2- or 3-Digit Display

Lists serviceable parts for control heads with 1-, 2-, or 3-digit displays, such as looms, keypads, and LCDs.

Chapter 17: TMAA01-01 Line-Interface Board

17.1 Operation

Explains the operation of the line-interface board, how to toggle it on/off with function keys, and radio programming.

17.3 Installing the Line-Interface Board

Provides a step-by-step procedure for installing the line-interface board, including parts required and tightening torques.

17.5 Interface Specification

Summarizes signals for the options-extender board on internal and external connectors, including pinouts and descriptions.

17.8 Circuit Description

Details the circuit description for the audio and logic interfaces of the line-interface board.