Intek M-790 Service Manual.pdf

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1、 Model No: 3391 Drawring No: Customer : Model No: M-790 Plus Rev,Date: M-790 Plus Service Manual Created by: Approved by: Rev.No: For Stage: Release Date: Page: 1 / 60 Model No: 3391 Drawring No: Customer : Title M-790 Plus Rev,Date: Table of Contents Page Specifications 3 Test and Alignment Procedu

2、re 4 Block Diagram 14 Schematic Diagram 15 Printed Circuit Board 25 Channel Frequency Charts 26 Parts List 38 Semiconductor Voltage Chart 48 Semiconductor Lead Assignment and Block Diagram 55 Exploded View Parts List 58 Exploded View 60 Created by: Approved by: Rev.No: For Stage: Release Date: Page:

3、 2 / 60 Model No: 3391 Drawring No: Customer : Title M-790 Plus Rev,Date: SPECIFICATIONS 1. GENERAL Channels. 400 Ch AM/FM 4W Frequency Range. .25.615 to 30.105 MHz FrequencyControl.PLL Operating Temperature Range.-10 / +55C DC Input Voltage.13.2 V DC 15% Size.180(L) X 35(H) X 140(D) mm Weight.0.850

4、 kg 2. RECEIVER Receiving System.Dual Conversion Super Heterodyne Intermediate Frequency.1st IF: 10.695 MHz, 2nd IF: 455 MHZ Sensitivity.0.5 V for 20 db SINAD in FM mode Audio Distortion.Less Than 8% 1 KHz ImageRejection.65 dB Adjacent ChannelRejection.65 dB Signal/ Noise Ratio.45 dB Current Drain a

5、t standby.325 mA 3. TRANSMITTER Output Power.4W 13.2 V DC Modulation.FM: 1.8 KHz 0.2 KHz Frequency response.From 400 Hz to 2.5 KHz Output impedance.RF 50 ohm Unbalance Signal/ Noise Ratio.40 dB MIN Current Drain.1300 mA Created by: Approved by: Rev.No: For Stage: Release Date: Page: 3 / 60 Model No:

6、 3391 Drawring No: Customer : Model No: M-790 Plus Rev,Date: 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 channe

7、l. 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

8、 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 cle

9、arly 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. Created by: Approved by: Rev.No: For Stage: Release Date: Page: 4 /

10、 60 Model No: 3391 Drawring No: Customer : Model No: M-790 Plus Rev,Date: THEORY OF OPERATIONS TRANSMITTER A. RF Amplification The output of double AMP Q301 is fed through tuning IFT L301 and L302 to the base of pre driver AMP Q302. The output is then supplied through tuning circuit L303 to RF drive

11、r AMP Q303. The output of Q303 is supplied with tuning circuit L304 and C317,C315,C21 and goes to the base of final RF AMP Q304. The output of Q304 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 A

12、MP Q304 and antenna, 4-stage “PHI” network L308, C324, C1, C327, L311, C337, C333, L312, C328, C334, C338, L313 serves as a spurious radiation suppressor . This network also serves to match the impedance between TX power AMP Q304 and the antenna. C. Circuit for Limiting Power After finished all alig

13、nment, the constant voltage supply circuit limits the available power 4 W or slightly less. RV1 and corresponding three transistors control supply voltage of RF amplifier and other circuits. Tune all the trimmer parts for maximum indication of RF power meter and adjust RV1 to make 4 w indication of

14、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 mic audio amplifier IC KIA324 which drives modulation varicap diode D403 in the VCO circ

15、uit. RV401 limits the incoming modulation audio levels to inhibit over modulation. While reading the modulation factor on the modulation analyzing equipment, adjust RV401 shall not exceed +-1.8 KHz/Dev. After 20 dB up from 1.25 KHz/1.2 KHz/Dev. Audio level b. AM Modulation signals are filtered with

16、RC network and goes to the audio power AMP IC IC103 to make nominal signal level to achieve wanted modulation. To control incoming audio signal, diode D203 and corresponding ALC circuit limits the modulation shall not exceed +/-80% adjust RV201 +/-80% modulation under 1.0 KHz AF 60% mod plus 20 dB o

17、f audio signal. Created by: Approved by: Rev.No: For Stage: Release Date: Page: 5 / 60 Model No: 3391 Drawring No: Customer : Model No: M-790 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

18、 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 Q105,Q106 mixes the incoming RF signal to generate first IF signal. Mixed signals were filtered w

19、ith 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 2nd IF filter was amplified and limits internaly. After amplification the signals fed the quadrature detector loop L104. Then we ca

20、n 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 Rem

21、edy 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 interna

22、l 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, VR1, IC102) Replace Replace Squelch

23、 does not work Defective VR1, RV2, IC2. Replace the defective components. Re-adjust Created by: Approved by: Rev.No: For Stage: Release Date: Page: 6 / 60 Model No: 3391 Drawring No: Customer : Model No: M-790 Plus Rev,Date: No modulation Defective microphone. Poor audio output and defective modulat

24、ion microphone amplifier components (IC103). Defective microphone connector components. Defective ALC circuit D413, D414. Replace Replace the defective components. Replace Replace the defective components. LCD meter does not work Defective D5.D3 Defective IC101. Defective RV101.RV202 Replace Replace

25、 Replace LCD display does not work Defective RED wire fuse. Defective IC101, Q414. Replace Replace Channel selector does not work Defective IC101, SW105. Replace EMG CH9.19 does not work Defective EMG SW. Defective IC101. Replace Replace Created by: Approved by: Rev.No: For Stage: Release Date: Page

26、: 7 / 60 Model No: 3391 Drawring No: Customer : Model No: M-790 Plus Rev,Date: ALIGNMENT PROCEDURE Step Setting Connection Adjuster Adjust for 1 Frequency adjustment MIC : Receive Volume : optional Squelch : optional CH selector : 19 EU CH9 : off Frequency counter to dummy load (Figure 1). CT201 27.

27、185MHz300Hz 2 VCO Voltage adjustment MIC : Receive Volume : optional Squelch : optional CH selector : 1A CH9 : OFF Connect DC voltmeter between R406, C411 and GND. (Figure 2). L501 1V at TX. Figure 1 Figure 2 Created by: Approved by: Rev.No: For Stage: Release Date: Page: 8 / 60 Model No: 3391 Drawr

28、ing No: Customer : Model No: M-790 Plus Rev,Date: TRANSMITTER SECTION Test Equipment Required RF power meter (RF SSVM) DC power supply (13.2 volt, 3 amp) 50 ohms dummy load (non-inductive) Spectrum analyzer RF attenuator (50 ohms non-inductive) Frequency counter Oscilloscope Coupler Audio generator

29、ALIGNMENT PROCEDURE Step Setting Connection Adjuster Adjust for 1 RF power stage MIC : Transmit Volume : optional Squelch : optional CH : selector : 19 CH9 : OFF Connect dummy load and RF power meter to the EXT-ANT jack on the set (Figure 3). L301 L302 L303 Maximum indication on the power meter (4 w

30、atts). If indication is not in 4 watts range, adjust L301, L302, L303. 2 Second harmonic check MIC : Transmit Volume : optional Squelch : optional CH : selector : 19 CH9 : OFF Connect RF power meter With dummy load to spectrum analyzer through coupler /-40 dB Attenuator to EXT-ANT jack on the set (F

31、igure 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 lower than 60 dB. Check for the other channels. 3 Frequency check MIC : Transmit Volume : optional Squelch : optional CH : selector : 19 C

32、H9 : OFF Connect dummy load and frequency counter though coupler to RF powermeter. Connect RF powermeter to EXT-ANT jack on the set (Figure 5). CT201 Be sure that the indication of the transmitter frequency is 27.185MHz300Hz on the frequency counter. Created by: Approved by: Rev.No: For Stage: Relea

33、se Date: Page: 9 / 60 Model No: 3391 Drawring No: Customer : Model No: M-790 Plus Rev,Date: 4 TX power level adjustment Volume : optional Squelch : optional CH : selector : 1 CH9 : OFF Connect dummy load and oscilloscope through Coupler to RF powermeter connect audio generator to microphone jack (Fi

34、gure 6). RV202 Adjust until the 5th bar appears on the channel display LCD. Figure 3 Created by: Approved by: Rev.No: For Stage: Release Date: Page: 10 / 60 Model No: 3391 Drawring No: Customer : Model No: M-790 Plus Rev,Date: Figure 4 RECEIVER SECTION Test Equipment Required RF Signal generator (RF

35、SG) 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 RF gain : Fully clockwise CH9 : OFF RFSG:27.185 MHz,1kHZ 1V , 1.2 K Dev. Con

36、nect RF signal generator to EXT-ANT jack. Connect SSVM and distortion meter with 8 ohm dummy load (Figure 7). L101 L102 L103 L104 L106 L401 L402 L403 Maximum indication on SSVM. Reduce output from RFSG until the audio output becomes about 500mW (2V). Created by: Approved by: Rev.No: For Stage: Relea

37、se Date: Page: 11 / 60 Model No: 3391 Drawring No: Customer : Model No: M-790 Plus Rev,Date: 2 Squelch adjustment MIC : Receive Volume : 50mW (2V) 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 t

38、o EXT speaker jack with 8 ohm dummy load (Figure 7). RV1 Adjust until the audio output appears. 3 RF signal meter adjustment MIC : Receive Volume : 500mW (2V) Squelch : Fully counter Clockwise RFSG: 27.185 MHz, 1kHZ, 1V, 1.2K Dev. Connect RF signal generator to EXT-ANT Jack. Connect SSVM and distort

39、ion meter to EXT speaker jack with 8 ohm dummy load (Figure 7). RV101 Adjust until the 3rd LED on the S/RF meter lights up. Figure 5 Created by: Approved by: Rev.No: For Stage: Release Date: Page: 12 / 60 Model No: 3391 Drawring No: Customer : Model No: M-790 Plus Rev,Date: Figure 6 Figure 7 Created

40、 by: Approved by: Rev.No: For Stage: Release Date: Page: 13 / 60 Created by: Approved by: Rev.No: For Stage: Release Date: Page: 16 / 60 INTEK M-790 ESP Model No: 3391 Drawring No: Customer : Model No: M-790 Plus Rev,Date: PLL CIRCUIT BLOCK DIAGRAM 1. INTRODUCTION The frequencies for transmitter and

41、 receiver first local frequencies are all derived from a single 4.5 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 1

42、0.240 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 gose to the double circuit Q301,L301,L302 which doubles the frequency to generate 26.965 MHz

43、(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 r

44、eceiver 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 Q506 into the first fed balanced mixer Q107,Q108 Created by: Approved by: Rev.No: For Stage: Release Date: Page: 17 / 60 Q 408 VCO Q 301 Doubler To Transmitter Model No

45、: 3391 Drawring No: Customer : Model No: M-790 Plus Rev,Date: 2. BASIC SYNTHESIZER SCHEME The crystal frequency (4.500 MHz) 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 75 of IC101. The feedback loop is closed by passing the phase detector output through an active low pass filter and using the output to co