The Kenwood TK 90 is a professional VHF FM transceiver designed for commercial and amateur radio communications. This service manual covers technical specifications, circuit descriptions, alignment procedures, troubleshooting, and maintenance guidelines for qualified service technicians. The TK 90 operates in the 136-174 MHz frequency range with 25W output power and features programmable channels, CTCSS/DCS capabilities, and robust construction for demanding environments.
Complete technical specifications and performance characteristics of the Kenwood TK 90 transceiver.
| Parameter | Specification |
|---|---|
| Frequency Range | 136-174 MHz |
| Output Power | 25W (High), 5W (Low) |
| Modulation | 16F3 (FM) |
| Channel Capacity | 16 channels programmable |
| Power Supply | 13.8V DC ±15% |
| Current Consumption | 5A max (TX), 0.8A (RX) |
| Dimensions | 140W × 40H × 165D mm |
| Weight | 1.2 kg |
| Sensitivity | 0.25μV (12dB SINAD) |
| Audio Output | 2W at 10% distortion |
Detailed explanation of the TK 90 circuit blocks and signal flow.
WARNING! High voltages present in transmitter stages. Use appropriate safety equipment.
Step-by-step alignment instructions for optimal performance.
CAUTION! Use calibrated test equipment. Follow procedures exactly.
System block diagrams showing signal flow and circuit interconnections.
Complete block diagrams included for:
Receiver Section: RF amp → Mixer → 1st IF → 2nd IF → Demodulator → Audio
Transmitter Section: Microphone → Compander → Modulator → Driver → PA → Antenna
Control Section: CPU → Display → Keypad → EEPROM → PLL
Printed circuit board layouts for component placement and troubleshooting.
Tip: Use anti-static precautions when handling PCBs.
Complete component listing with part numbers and descriptions.
| Part Number | Description | Qty |
|---|---|---|
| X50-1230-01 | Main PCB Assembly | 1 |
| X50-1231-01 | Front Panel Assembly | 1 |
| X50-1232-01 | RF Power Module | 1 |
| X50-1233-01 | LCD Display | 1 |
| X50-1234-01 | Microprocessor IC | 1 |
| X50-1235-01 | PLL IC | 1 |
| X50-1236-01 | Final Transistor | 1 |
Systematic troubleshooting procedures for common problems.
| Symptom | Possible Cause | Corrective Action |
|---|---|---|
| No power | Power supply/fuse | Check 13.8V input; replace 5A fuse |
| No transmit | PA stage/PLL | Check final transistor; verify PLL lock |
| Poor reception | RF amp/alignment | Check RF transistors; realign receiver |
| No audio | Audio IC/speaker | Check audio amplifier IC; test speaker |
| Display issues | Ribbon cable/CPU | Reseat display cable; check CPU voltages |
Recommended maintenance intervals and procedures.
Monthly: Clean exterior, check connections, verify operation
Quarterly: Performance check, alignment verification
Annually: Complete alignment, component inspection, preventive maintenance
WARNING! Only qualified technicians should perform internal maintenance.
Important safety information for service personnel.
RF Exposure: Maintain safe distance from antenna during transmission
Electrical Safety: Disconnect power before servicing; discharge capacitors
ESD Protection: Use grounded workstations and wrist straps
Ventilation: Ensure adequate cooling during extended operation
Additional service information and technical notes.
Firmware Updates: Available from Kenwood service website
Calibration: Requires spectrum analyzer and communication service monitor
Warranty: 1 year limited warranty from date of purchase
Service Centers: Authorized Kenwood service centers nationwide
Contact: Kenwood Technical Support: 1-800-KENWOOD