Realisitic TRC-476
Documentation Project

CBTricks.com

PLL & Transmitter Alignment

 

Phase Locked Loop and CPU Section

Test Equipment Required
a.    Frequency Counter
b.    DC Power Supply (13.8 Volt. 3 Amp.)
c.    DC Voltmeter
d.    Oscilloscope

Alignment Procedure

Step

Setting

Connection

Adjust

Adjust for

1

Frequency adjustment:
MIC: Receive
Volume: Optional
Squelch: Optional
CH Selector: Optional
RF Gain: Optional
Function: CB/PA PA, ANL, NB,
CH9: OFF

Frequency counter to output pin 20 of IC501

C528

10.240MHz ± 100Hz

2

RX VCO voltage adjustment:
MIC: Receive
Volume: Optional
Squelch: Optional
CH Selector: 1
RF Gain: Optional
Function: CR/PA PA, ANL, NB,
CH9: OFF

Connect DC voltmeter between R527 and R531

L501

2V

3

TX VCO voltage adjustment:
MIC: Transmit
Volume: Optional
Squelch: Optional
CH Selector: 1
RF Gain: Optional
Function: CB/PA PA, ANL, NB,
CH9: OFF

Connect DC voltmeter between R527 and R531

L501

Indication on DC voltmeter must be 1.5-2.5 Volt. If DC voltmeter does not indicate 1.5-2.5 volt, readjust L501.

4

CPU IC Voltage check:
MIC: Receive
Volume: Optional
Squelch: Optional
CH selector: Optional
RF Gain: Optional
Function: CB/PA PA, ANL, NB,
CH9: OFF

Connect DC voltmeter to pin 24 of IC501

 

Indication on DC voltmeter must be 5- 6V volt.

5

CPU frequency check:
MIC: Receive
Volume: Optional
Squelch: Optional
CH Selector: Optional
RF Gain: Optional
Function: CR/PA PA, ANL, NB,
CH9: OFF

Connect oscilloscope to pin 8 and 9 of IC501

 

Check for 160 Hz of square waveform on the oscilloscope

 

Transmitter Section

Test Equipment Required

a. RF Powermeter (RF SSVM) f. DC Power Supply (13.8 Volt, 3 Amp.)
b. 50 ohm load (non-inductive) g. Spectrum Analyzer
c. RF Attenuator h. Frequency Counter
d. Oscilloscope i. Coupler
e. Audio Generator j. Dummy Load

Alignment procedure

 

Step

Setting

Connection

Adjust

Adjust for

1

RF Driver stage:
MIC: Transmit
Volume: Optional
Squelch: Optional
CH Selector: 19
RF Gain: Optional
Function: CR/PA PA, ANL, NB,
CH9: OFF

Connect oscilloscope to base of Q302

L302

Maximum waveform on the oscilloscope.

2

RF Power stage:
MIC: Transmit
Squelch: Optional
Volume: Optional
CH Selector: 19
RF Gain: Optional
Function: CR/PA PA, ANL, NB,
CH9: OFF

Connect dummy load and RF powermeter to the EXT-ANT. Jack on the set

L303
L304
L305
L306

Maximum indication on the powermeter (4 watts). If indication is not in 4 watts range, readjust L301, L302, L303, L304, L305, L306

3

Second harmonic check:
MIC: Transmit
Volume: Optional
Squelch: Optional
CH Selector: 19
RF Gain: Optional
Function: CB/PA PA, ANL, NB,
CH9: OFF

Connect RF powermeter with dummy load to spectrum analyzer through coupler/ -40dB attenuator to EXT-ANT. Jack on the set

 

At no modulation, compare the level of fundamental frequency to the level of harmonic frequency. Suppression of the 2nd harmonic frequency level must be lower than - 60dB. Check for the other channels.

4

Frequency check:
MIC: Transmit
Volume: Optional
Squelch: Optional
Channel selector: 19
RF Gain: Optional
Function: CR/PA PA, ANL, NB,
CH9: OFF

Connect dummy load and frequency counter through coupler to RF powermeter. Connect RF powermeter to EXT-ANT jack on the set.

C528

Make sure that the indication of the transmitter frequency is 27.185MHz ± 300Hz on the frequency counter.

5

TX Power LED adjustment:
MIC: Transmit
Volume: Optional
Squelch: Optional
Channel Selector: 1
RF Gain: Optional
Function: CR/PA PA, ANL, NB,
CH9: OFF

Connect dummy load and oscilloscope through coupler to RF powermeter. Connect RF powermeter to EXT-ANT Jack on the set

RV202

Adjust until the 3rd LED light up at 4 watts RF output power.

 


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we cannot guarantee that the instructions will work on every radio presented.