Intek H-520 PLUS User manual

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H 520 PLUS
Service Manual

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Table of Contents
Page
Specifications 3
TestandAlignmentProcedure 8
BlockDiagram 13
SchematicDiagram 14
PrintedCircuitBoard 23
ChannelFrequencyCharts 25
PartsList 40
SemiconductorVoltageChart 45
Semiconductor Lead Assignment and Block Diagram 53
ExplodedViewPartsList 56
ExplodedView 57

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SPECIFICATIONS
1. GENERAL
Channels………………………...……………………………………………………................... 400 Ch AM/FM 4W
Frequency Range………………………………...…………………………..……………......25.615 to 30.105 MHz
FrequencyControl………………………………………………………………………………..…………..…….……PLL
Operating Temperature Range……………………………………..……..……………………………-10°/ +50°C
DC Input Voltage…………………………………………………....………………………..………....9.0 V DC ±15%
Size………………………………………………………………….……..………..….…140(L) X 60(W) X 30(H) mm
Weight………………………………………………………………………………..…………..……...……..……0.50 kg
2. RECEIVER
Receiving System……………………………….…………………………....Dual Conversion Super Heterodyne
Intermediate Frequency…………………………………………...…….…1st IF: 10.695 MHz, 2nd IF: 455 MHZ
Sensitivity……………………………………….…..............................….0.5 µV for 20 db SINAD in FM mode
Audio Distortion……………………………………………………….….……..…………….Less Than 8% @ 1 KHz
Image Rejection……………………………………….…………………..………………………………………...60 dB
Adjacent Channel Rejection………………………………………….…………………………………………....60 dB
Signal/ Noise Ratio…………………………….…………………………….…………………………………..….45 dB
Current Drain at standby……………………….…………………………………………………………..……..60 mA
3. TRANSMITTER
Output Power…………………………………………………………………………………..……...….4W @ 9.0 V DC
Modulation………………………………………………………………..………….…...………FM: 1.6 KHz ±0.2 KHz
Frequency response…………………………………………….…................................From 300 Hz to 3.0 KHz
Output impedance………………………………………………………………………………RF 50 ohm Unbalance
Signal/ Noise Ratio…………………………………………………………………………………..………..40 dB MIN
Current Drain…………………………………………………………………………………………….….…….1300 mA

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OPERATION INSTRUCTIONS
Having properly installed your batteries and hooked-up the antenna, you are now ready to operate your radio for
optimum reception and voice transmission.
Turn the power “ON” with ON/OFF switch.
Set the desired channel.
Adjust the squelch control knob to reduce any undesirable background noise when no signal is being received. To
do this, select a channel where no signal are present, or wait until signals cease on your channel. Then, rotate
the squelch control knob clockwise to a point where the background noise disappears.
Note: When the squelch is set properly, the speaker will remain quiet until a signal is
received. In order to receive weak signals, do not set the squelch too high.
Adjust the volume to the desired listening level.
To Transmit
Press and hold the push-to-talk button. Speak slowly and clearly in a normal voice two to three inches from the
microphone. A buit-in modulation control circuit will automatically adjust the microphone input level. There is no
need to speak loudly.
To Receive
Release the push-to-talk button.

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THEORY OF OPERATIONS
TRANSMITTER
A. RF Amplification
The output of double AMP Q201 is fed through tuning T203 and T204 to the base of pre driver AMP Q202. The
output is then supplied to RF driver AMP Q203. The output of Q203 is supplied with tuning circuit L204 and C214,
C215, C216 and goes to the base of final RF AMP Q204. The output of Q204 is supplied to the antenna through
L-C tuning circuit.
B. Circuit for Suppression of Spurious Radiation
The tuning circuit between the output of final AMP Q204 and antenna, 5-stage “PHI” network C221, C219, C220,
L206, C223, C245, L207, C241, C228, C240, L208, C242, C230, C229, L209, C234, C233, C232, L210, C243,
C235, C236 serves as a spurious radiation suppressor . This network also serves to match the impedance
between TX power AMP Q204 and the antenna.
C. Circuit for Limiting Power
After finished all alignment, the constant voltage supply circuit limits the available power 4 W or slightly less.
RV501 and corresponding three transistors Q509, Q502, Q501 control supply voltage of RF amplifier and other
circuits.
Tune all the trimmer parts for maximum indication of RF power meter and adjust RV501 to make 4 w indication
of RF power meter.
The tuning is adjusted so that the actual power is from 3.8 to 4.0 W. There are no other additional controls for
adjusting the TX output power.
D. Modulation Control
a. FM
The mic input is fed to audio amplifier IC KIA324 which drives modulation varicap diode D302 in the VCO circuit.
RV701 limits the incoming modulation audio levels to inhibit over modulation. While reading the modulation factor
on the modulation analyzing equipment, adjust RV701 shall not exceed +/-1.6 KHz/Dev. After 20 dB up from
1.25 KHz/1.2 KHz/Dev. Audio level
b. AM

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Modulation signal is fed to audio amplifier IC KIA324 and goes to TX voltage regulate circuit Q509, Q502, Q501 to
make nominal signal level to achieve wanted modulation. To control incoming audio signal, R272 and
corresponding ALC circuit limits the modulation shall not exceed +/-60% adjust RV702 +/-60% modulation under
1.0 KHz AF 60% mod plus 20 dB of audio signal.
E. Receiver
CB receiver is dual conversion supper-heterodyne type with the first IF 10.695 MHz and second IF 455 KHz.
Receiver is separated two blocks, 1st IF section and 2nd IF section.
The PLL synthesizer supplies first local frequency 16.270 ~ 16.710 MHz.(for EU) and 16.90625 MHz ~ 17.29625
MHz (for UK) With the provided first local frequencies Q102,Q103 mixes the incoming RF signal to generate first
IF signal. Mixed signals were filtered with the CF101 (10.695 MHz) crystal filter and other tuning circuits. Output
signal of mixer is filtered with CF102 (455 KHz ceramic filter). The 455 KHz signal from the 2nd IF filter was
amplified and limits internally. After amplification the signals fed the quadrature detector loop T104. Then we can
see the recovered audio signals on Pin 12 for FM and Pin 13 for AM of IC1.

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TROUBLE SHOOTING HINTS
Symptom Probable Cause Remedy
Unit does not work
at all
•Defective power switch VR601.
•Empty Battery.
•Broken wire Battery.
•Defective D501.
•Replace
•Replace
•Replace
•Replace
No output from
speaker at all
•Defective external speaker jack.
•Wire speaker open.
•Defective internal speaker.
•Defective VR601, IC601, Q601 other components.
•Repair or replace
•Replace
•Replace
•Replace the defective
components.
No noise on
speaker
•Measure all the voltage of IC601,102 with voltage
chart
•Defective squelch circuit components (RV101,
VR102, IC102)
•Replace
•Replace
Squelch does not
work
•Defective VR102, RV101, IC102.
•Replace the defective
components.
•Re-adjust
No modulation
•Defective RV702.
•Defective microphone or EXT microphone jack.
•Poor audio output and defective modulation
microphone amplifier components (IC103).
•Defective microphone wire connector.
•Replace
•Replace
•Replace the defective
components.
•Replace
LCD display does
not work
•Defective LED.
•Defective Q803.
•Replace
•Replace

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ALIGNMENT PROCEDURE
Step Setting Connection Adjuster Adjust for
1
Frequency adjustment
MIC : Receive
Volume : optional
Squelch : optional
CH selector : 19
Frequency counter to
dummy load (Figure
1).
X302 27.185MHz±300Hz
2
VCO Voltage adjustment
MIC : Receive
Volume : optional
Squelch : optional
CH selector : 19
Connect DC
voltmeter at test
point1
(Figure 2).
T302 1.4V at RX.
Figure 1 Figure 2

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TRANSMITTER SECTION
Test Equipment Required
•RF power meter (RF SSVM) •DC power supply (9.0 volt, 3 amp)
•50 ohms dummy load (non-inductive) •Spectrum analyzer
•RF attenuator (50 ohms non-inductive) •Frequency counter
•Oscilloscope •Coupler
•Audio generator
ALIGNMENT PROCEDURE
Step Setting Connection Adjuster Adjust for
1
RF power stage
MIC : Transmit
Volume : optional
Squelch : optional
CH : selector : 19
Connect dummy load and
RF power meter to the
EXT-ANT jack on the set
(Figure 3).
T203
T204
Maximum indication on
the power meter (4
watts). If indication is
not in 4 watts range,
adjust T203, T204.
2
Second harmonic check
MIC : Transmit
Volume : optional
Squelch : optional
CH : selector : 19
Connect RF power meter
With dummy load to
spectrum analyzer through
coupler /-40 dB
Attenuator to EXT-ANT jack
on the set
(Figure 4).
At no modulation,
compare the level o
fundamental frequency
to the level of harmonic
frequency. Suppression
of the 2nd harmonic
frequency level must be
3
Frequency check
MIC : Transmit
Volume : optional
Squelch : optional
CH : selector : 19
Connect dummy load and
frequency counter though
coupler to RF power meter.
Connect RF power meter to
EXT-ANT jack on the set
(Figure 5).
X302 Be sure that the
indication of the
transmitter frequency is
27.185MHz±300Hz on
the frequency counter.
4
TX power adjustment
Volume : optional
Squelch : optional
CH : selector : 19
Connect dummy load and
oscilloscope through
Coupler to RF power meter
connect audio generator to
microphone jack
(Figure 6).
RV501 Adjust until
3.6-4 Watts

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Figure 3
Figure 4

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RECEIVER SECTION
Test Equipment Required
•RF Signal generator (RFSG)
•SSVM
•Distortion meter
•DC power supply
ALIGNMENT PROCEDURE
Step Setting Connection Adjuster Adjust for
1
Audio output adjustment
MIC : Receive
Volume : Fully clockwise
Squelch: Turn to-
Counter clockwise
CH selector : 19
RFSG:27.185 MHz,1kHZ
1µV , 1.2 K Dev.
Connect RF signal
generator to EXT-ANT
jack. Connect SSVM and
distortion meter with 8
ohm dummy load
(Figure 7).
T102
T103
Maximum indication on
SSVM. Reduce output
from RFSG until the
audio output becomes
about
600mV.
2
Squelch adjustment
MIC : Receive
Volume : 600mV
Squelch : Clockwise
CH selector : 19
RFSG:27.185MHz, 1kHZ
1mV, 1.2K DEV.
Connect RF signal
generator to EXT-ANT
Jack. Connect SSVM and
distortion meter to EXT
speaker jack with 8 ohm
dummy load
(Figure 7).
RV101 Adjust until the audio
output appears.
3
Auto Squelch adjustment
MIC : Receive
Volume : 600mV
Squelch : Auto Squelch on
CH selector : 19
RFSG:27.185MHz, 1kHZ
1uV, 1.2K DEV.
Connect RF signal
generator to EXT-ANT
Jack. Connect SSVM and
distortion meter to EXT
speaker jack with 8 ohm
dummy load
(Figure 7).
RV103 Adjust until the audio
output disappears.

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Figure 5
Figure 6
Figure 7

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PLL CIRCUIT BLOCK DIAGRAM
1. INTRODUCTION
The frequencies for transmitter and receiver first local frequencies are all derived from a single 10.240 MHz
crystal by means of a phase locked loop. The first local oscillator frequencies are 16.270 MHz (CH 1) to 16.710
MHz (CH 40) for EU and 16.90625 MHz (CH 1) to 17.29625 MHz (CH 40) for UK. The second local frequency is
fixed at 10.240 MHz to generate second IF 455 KHz. During transmit, The VCO of the PLL operates 13.4825 MHz
(CH 1) to 13.7025 MHz (CH 40) for EU, 13.800625 MHz (CH 1) to 13.995625 MHz (CH 40) for UK the VCO
frequency goes to the double circuit Q201, T203, T204 which doubles the frequency to generate 26.965 MHz (CH
1) to 27.405 MHz (CH 40) for EU and 27.60125 MHz (CH 1) to 27.99125 MHz (CH 40) for UK
13.4825 MHz (CH 1) EU 26.965 MHz (CH 1)
13.7025 MHz (CH 40) EU 27.405 MHz (CH 40)
13.800625 MHz (CH 1) UK 27.60125 MHz (CH 1)
13.995625 MHz (CH 40) UK 27.99125 MHz (CH 40)
The VCO operating frequency for the receiver is 16.270, 16.90625 MHz (CH 1) to 16.710, 17.29625 MHz (CH 40)
as the first local oscillator, injected through the buffer AMP Q302 into the first fed balanced mixer Q102, Q103.
Q 201
VCO
T203,T204
Doubler
T
o Transmitte
r

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2. BASIC SYNTHESIZER SCHEME
The crystal frequency (10.240MHz) is divided by 1800 times to make 2.5 KHz which is fed to one side of the
phase detector. The VCO output is divided by a programmable divider, and fed to other side of the phase
detector Pin 11 of IC302. The feedback loop is closed by passing the phase detector output through an active low
pass filter and using the output to control the VCO frequency through varicap diode D301.
Under locked conditions, both of phase detector input signal must be indential at 2.5 KHz. The VCO frequency is
then given by:
FVCO / N = 0.0025 MHz or FVCO = 0.0025 x N MHz
Since “N” is an integer, the VCO frequency can be stepped up with 2.5 KHz increments. By suitable choice of “N”
the desired output frequency can be obtained.
Channel 1 Channel 40
N FVCO N FVCO Function
Transmit 5393 13.4825 5481 13.7025
Receive 6508 16.2700 6684 16.7100
EU
Transmit 5520.25 13.800625 5598.25 13.995625
Receive 6762.50 16.90625 6918.5 17.29625
UK
(SEE TABLE FOR OTHER CHANNELS)

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The VCO frequency goes to the double circuit, which doubles the incoming signals.
Double output Frequency
Transmit
_______
Transmit
_______
CH 1, 13.4825 MHz
CH 1, 13.800625 MHz
CH 40, 13.7025 MHz
CH 40, 13.995625 MHz
26.965 MHz
27.60125 MHz
27.405 MHz
27.99125 MHz
Since all frequencies are obtained from the crystal controlled PLL oscillator, all outputs are coherent with the
crystal oscillator frequency and maintaining the same percentage accuracy.
INTERNAL BLOCK DIAGRAM

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DIVIDE RATIO, VCO RX/TX FREQUENCIES FOR EACH CHANNEL OF “EU”
RX TX
Channels Frequencies
(MHz)
N
Frequencies MHz
N
Frequencies MHz
1 26.965 6508 16.27 5393 13.4825
2 26.975 6512 16.28 5395 13.4875
3 26.985 6516 16.29 5397 13.4925
4 27.005 6524 16.31 5401 13.5025
5 27.015 6528 16.32 5403 13.5075
6 27.025 6532 16.33 5405 13.5125
7 27.035 6536 16.34 5407 13.5175
8 27.055 6544 16.36 5411 13.5275
9 27.065 6548 16.37 5413 13.5325
10 27.075 6552 16.38 5415 13.5375
11 27.085 6505 16.39 5417 13.5425
12 27.105 6512 16.41 5421 13.5525
13 27.115 6516 16.42 5423 13.5575
14 27.125 6524 16.43 5425 13.5626
15 27.135 6528 16.44 5427 13.5675
16 27.155 6532 16.46 5431 13.5775
17 27.165 6536 16.47 5433 13.5825
18 27.175 6544 16.48 5435 13.5875
19 27.185 6548 16.49 5437 13.5925
20 27.205 6552 16.51 5441 13.6025
21 27.215 6608 16.52 5443 13.6075
22 27.225 6612 16.53 5445 13.6125
23 27.255 6624 16.56 5451 13.6275
24 27.235 6616 16.54 5447 13.6175
25 27.245 6620 16.55 5449 13.6225
26 27.265 6628 16.57 5453 13.6325
27 27.275 6632 16.58 5455 13.6375
28 27.285 6636 16.59 5457 14.6425
29 27.295 6640 16.60 5459 13.6475
30 27.305 6644 16.61 5461 13.6525
31 27.315 6648 16.62 5463 13.6575
32 27.325 6652 16.63 5465 13.6625
33 27.335 6656 16.64 5467 13.6675
34 27.345 6660 16.65 5469 13.6725
35 27.355 6664 16.66 5471 13.6775
36 27.365 6668 16.67 5473 13.6825
37 27.375 6672 16.68 5475 13.6875
38 27.385 6676 16.69 5477 13.6925
39 27.395 6680 16.70 5479 13.6975
40 27.405 6684 16.71 5481 13.7025

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DIVIDE RATIO, VCO RX/TX FREQUENCIES FOR EACH CHANNEL OF “UK”
RX TX
Channels Frequencies
(MHz) Frequencies MHz Frequencies MHz
1 27.60125 6546.5 16.90625 5412.25 13.800625
2 27.61125 6766.5 16.91625 5522.25 13.805625
3 27.62125 6770.5 16.92625 5524.25 13.810625
4 27.63125 6774.5 16.93625 5526.25 13.815625
5 27.64125 6778.5 16.94625 5528.25 13.820625
6 27.65125 6782.5 16.95625 5530.25 13.825625
7 27.66125 6786.5 16.96625 5532.25 13.830625
8 27.67125 6790.5 16.67625 5534.25 13.835625
9 27.68125 6794.5 16.98625 5536.25 13.840625
10 27.69125 6798.5 16.99625 5538.25 13.845625
11 27.70125 6802.5 17.00625 5540.25 13.850625
12 27.71125 6806.5 17.01625 5542.25 13.855625
13 27.72125 6810.5 17.02625 5544.25 13.860625
14 27.73125 6814.5 17.03625 5546.25 13.865625
15 27.74125 6818.5 17.04625 5548.25 13.870625
16 27.75125 6822.5 17.05625 5550.25 13.875625
17 27.76125 6826.5 17.06625 5552.25 13.880625
18 27.77125 6830.5 17.07625 5554.25 13.885625
19 27.78125 6834.5 17.08625 5556.25 13.890625
20 27.79125 6838.5 17.09625 5558.25 13.895625
21 27.80125 6842.5 17.10625 5560.25 13.900625
22 27.81125 6846.5 17.11625 5562.25 13.905625
23 27.82125 6850.5 17.12625 5564.25 13.910625
24 27.83125 6854.5 17.13625 5566.25 13.915625
25 27.84125 6858.5 17.14625 5568.25 13.920625
26 27.85125 6861.5 17.15625 5570.25 13.925625
27 27.86125 6866.5 17.16625 5572.25 13.930625
28 27.87125 6870.5 17.17625 5574.25 13.935625
29 27.88125 6874.5 17.18625 5576.25 13.940625
30 27.89125 6878.5 17.19625 5578.25 13.945625
31 27.90125 6882.5 17.20625 5580.25 13.950625
32 27.91125 6886.5 17.21625 5582.25 13.955625
33 27.92125 6890.5 17.22625 5584.25 13.960625
34 27.93125 6844.5 17.23625 5586.25 13.965625
35 27.94125 6898.5 17.24625 5588.25 13.970625
36 27.95125 6902.5 17.25625 5590.25 13.975625
37 27.96125 6906.5 17.26625 5592.25 13.980625
38 27.97125 6910.5 17.27625 5594.25 13.985625
39 27.98125 6914.5 17.28625 5596.25 13.990625
40 27.99125 6918.5 17.29625 5598.25 13.995625