Intek M-490 Plus - Receiver Description; TROUBLESHOOTING HINTS

Model No: 3390 Drawring No:
Customer :
Title
M-490 Plus
Rev,Date:
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, 1
st
IF section and 2
nd
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 Q105,Q106 mixes the incoming RF
signal to generate first IF signal. Mixed signals were filtered with the XF101 (10.695 MHz) crystal filter
and other tuning circuits. Output signal of mixer is filtered with CF101 (455 KHz ceramic filter). The 455
KHz signal from the 2
nd
IF filter was amplified and limits internaly. After amplification the signals fed the
quadrature detector loop L104. Then we can see the recovered audio signals on Pin 11 for FM of
IC102. With the amplitude of recovered signals, Q112 serves as an audio amplifier. For AM signal Will
be pass filter CF101 and induced to Q116, Q117 respective and detected to voice signal by D111.
TROUBLESHOOTING HINTS
Symptom
Probable Cause Remedy
Unit does not
work at all
•
Defective power switch VR102.
•
Blown fuse.
•
Broken DC power cord.
•
Defective IC101.
•
Replace
•
Replace
•
Replace
•
Replace
No output from
speaker at all
•
Defective external speaker jack.
•
Poor connection on microphone connector
•
Defective push switch on microphone.
•
Defective internal speaker.
•
Defective VR102, IC103 other components.
•
Repair or replace
•
Repair or replace
•
Repair or replace
•
Replace
•
Replace the defective
components.
No noise on
speaker
•
Measure all the voltage of IC102 with voltage
chart
•
Defective squelch circuit components (RV102,
VR108, IC102)
•
Replace
•
Replace
Squelch does not
work
•
Defective VR108, RV2, IC2.
•
Replace the defective
components.
•
Re-adjust
Created by: Approved by: Rev.No:
For Stage: Release Date: Page: 6 / 61