Receiver Section - Kenwood TM-271A Service Manual

Item Condition
6. MAX 1) CH : TX low (Wide)
deviation CH : TX center (Wide/Narrow)
CH : TX high (Wide)
2) AG : 1kHz/50mV
3) Transmit
7. MIC 1) CH : TX center (Narrow)
sensitivity 2) AG : 1kHz/5.4mV (TM-271A)
AG : 1kHz/2.4mV (TM-271E)
3) Transmit
8. CTCSS 1) CH : TX low (Wide)
fine CH : TX center (Wide/Narrow)
deviation CH : TX high (Wide)
2) Transmit
9. DCS fine 1) CH : TX low (Wide)
deviation CH : TX center (Wide/Narrow)
CH : TX high (Wide)
2) Transmit
10. DTMF 1) CH : TX center (Wide/Narrow)
fine 2) Transmit
deviation
If normal power is not obtained, please follow the
step below
Open the shielding cover (upper), and screw 3 locations
around ANT pin.
1. Switch off the transceiver.
Impedance of Final FET (Q504) and Drive FET (Q503) can
be measured easily using DVM Ω mode.
Normal condition – Gate : 20kΩ~50kΩ, Drain : 1MΩ~2MΩ
The above impedance values are rough estimations.
2. Switch on the transceiver. Check the voltage at F501 out-
put point.
The voltage is around 13.8V in receiving condition. The
voltage will be 12.6V~ in transmitting condition. If found
0V at this point then F501 is broken.
3. Remove R516.

Receiver Section

Item
Condition
1. Band pass 1) CH : RX low (Wide)
tuning CH : RX center (Wide/Narrow)
CH : RX high (Wide)
2) SSG output
: –121dBm (0.2µV) (Wide)
: –119dBm (0.25µV) (Narrow)
Mod : 1kHz
Dev : ± 3.0kHz (Wide)
Dev : ± 1.5kHz (Narrow)
ADJUSTMENT
Measurement
Test equipment Terminal
Modulation analyzer ANT
or Linear detector MIC
(LPF : 15kHz)
Oscilloscope
AG
AF V.M
Modulation analyzer
or Linear detector
(LPF : 3kHz)
Oscilloscope
4. Connect 50Ω load at the ANT location.
Transmit and check current drain at High power mode.
If the current drain is less than 1A, then Final FET is bro-
ken.
If the current drain is less than 5.0A, short the Drive FET
gate to ground, and check the current drain.
If the current drain is not 0.1A less than the original value,
then the Drive FET is broken.
5. Check input power level at Drive FET gate location.
Connect the wire to [RF] location.
Transmit and check for power to be within the range of
0.3W~0.6W.
If power found is less than 0.3W, check the circuit before
the Drive FET.
Measurement
Test equipment Terminal
SSG ANT
Oscilloscope EXT. SP knob
AF V.M
Distortion meter
TM-271A/271E
Adjustment
Parts Method
Encoder ± 4.0kHz (Wide)
± 2.0kHz (Narrow)
knob
According to the large +, –
Check
Encoder ± 0.75kHz (Wide)
± 0.35kHz (Narrow)
knob
± 0.75kHz (Wide)
± 0.35kHz (Narrow)
± 3.0kHz (Wide)
± 1.5kHz (Narrow)
Adjustment
Parts Method
Encoder Adjust to maximum SINAD.
Specifications/
Remarks
± 100Hz (Wide)
± 50Hz (Narrow)
± 1.2~1.9kHz
(Narrow)
± 50Hz
± 50Hz (Wide)
± 40Hz (Narrow)
± 200Hz (Wide)
± 100Hz (Narrow)
Specifications/
Remarks
SINAD
: 12dB or higher
25