Kenwood TR-7400A Service Manual
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Kenwood TR-7400A Service Manual

Kenwood TR-7400A Service Manual

2m fm transceiver
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Summary of Contents for Kenwood TR-7400A

  • Page 1 http://www.Datasheet4U.com...

  • Page 2: Table Of Contents

    ........... SPECIFICATIONS ......FINAL TRANSISTOR SPECIFICATIONS .......... BLOCK DIAGRAM ........CIRCUIT DESCRIPTION ......... PARTS ALIGNMENT PC BOARD ........PA UNIT (X45-1090-10) ........PD UNIT (X50-1380-10) ........VCO UNIT (X50.1370.10) ......INDICATOR UNIT (X54-1210-10) ........RX UNIT (X55-1150-10) ........TX UNIT (X56-1230-10) ..........

  • Page 3: Specifications

    Transistors FETs I Cs Diodes 144.00 to 147.995 MHz Digital (TTL Logic) control of phase locked VCO Less than k750 Hz at 25"~ -20 to +50°c 11.5 VDC to 16.0 VDC (13.8 VDC as reference) Negative grounding Less than 1A in receive with no input signal Less than 8A in transmit (HI) Less than 4.5A in transmit (LOW) (at 13.8 VDC)

  • Page 4: Final Transistor Specifications

    Stud Tstg V cso VCEO VEBO torque TA=~~"c "c inIb Unit -65 to Ratings Standard value Symbol LTPD level Unit Condition Minimum Maximum ICBO 15 V BVCES 15 mA 100 mA BVCEO BVEBO 5 mA 5V, IC 15V, f =0.1 MHz 12.5 V, POUT =30W 175 MHz, 12.5 V, POUT =30W...

  • Page 5: Block Diagram

    -.(b T-----~---- I114171919151 POWER SW TLR-313x6 L--------,- DISPLAY UNIT (X54-1210- 10) 13.8V DISPLAY UNIT (X54- 121 0- 10) r---------- DEC. DRIVER VCO UNlT (X50- SN7447AN X 3 r------ SWITCH BOARD (BCD 400-799) - - - - - - - - - - - - - - - - - - - - ~lvl~-N(1/537- 1/936)
  • Page 6 ---- ------- ---------- -------- TX, RX...
  • Page 7 Afr and Af,! are the frequency deviations of the REF OSC and LOCAL OSC respectively. You will see how the VCO The TR-7400A incorporates new1 y developed circuit frequency changes with the deviations and N preset in the techniques such as a PLL frequency synthesizer as the local oscillator.
  • Page 8 -" " Charge No. 1 pump No.2 To 013 (OFF circuit of VCO output) UNLOCK Indicator Fig. 3 PHASE DETECTOR Block Diagram...

  • Page 10: Circuit Description

    H8D5022 ---A Dlsc Output L.P.F. Fig. 5 TONE SQUELCH Circuit...
  • Page 11 VCT CIRCUIT The equipment incorporates a VCT circuit at the out- Parts number put side of the transmission mixer to improve spurious radiation and output levels in the wide range from 144 to 88.5 L79-0408-05 148 MHz. Varicaps D2, 3 and 4 are connected to tuning 94.8 L79-0409-05 coils L11, 12 and 13 through temperature compensation...

  • Page 12: Parts Alignment

    (838-0302-05) (838-0301-05) Knob (MAIN) sub panel Knob (5 kHz) Knob (TX OFFSET) (A22-0701~03) (K29-0702-04) (K23-0702-04) Mounting bracket Mounting rail Earphone jack stopper (J90-0045-04) (E 11-0003-1 5) (J51-0006-15) 4P socket (E08~047 1-05) Heat sink (F 20-0502-05)
  • Page 13 RF meter ADJ. (X56-1230-10) ~V'AVR Tone oscillator module PA UNlT (option) (X45-1090-10) VCO UNIT RX UNIT Center meter point (X50-1370-10) (X55-1 150-10) meter ADJ. TON< UNIT ~rotecti6n ADJ loption) SWITCH BOARD Tone dev. ADJ. Herical resonator...
  • Page 15 i""l f""i 2SC460 (B) 2SC733 (Y) TD3410AP TD3493EP 2SC458 (B) 2SA495 (Y1 TD3420AP MC4044P MC74416P 1234 5678 1234567 r PC BOARD FOR SWITCH (525-2506-131 PC BOARD FOR CHOKE (525-2507-041...

  • Page 18: Rx Unit (X55-1150-10)

    Coh]n =am- -,LO ->LO Eh]~ 0 .. Or;. hlF'n Lo'g= a-"- Lo'Efl"' *-r-. " " m c\i O,%n *- G yJ" sb', Ln-0 "m' h]-2 "hlr; --hl...
  • Page 20 ~18-0802.05 E22-0207-05 CE04WlA470 Electrolytic 47~F 10WV E23-0047.04 Terminal x 1 I CK45FlH103Z Ceramic 0.01~F +80%,-20% E30-0355.05 Wire (for speaker) CK45D1 H102M Ceramic lOOOpF f20% E31-0403-05 Connector with lead CK45F1 H103Z Ceramic 0.01~F +SO%,-20% E31-0404.15 Connector with lead CC45SLlHIOI K Ceramic IOOpF E31-0405-05 Connector...

  • Page 21: Parts List

    M type connector 2P connector (jack) Earth lug x 2 Terminal x 12 ~ ; i ~32.0703.14 Hexagonal boss x 5 UNIT (X50-1370-10) CAPACITOR CQ92MlH103K Mylar 0.01pF *lo% CQ92M1 H223K Mylar 0.022pF CE04WlC100 Electrolytic 10pF 16WV CQ92M1 H223K Mylar 0.022pF CQ92MlH102K Mylar 1000pF...
  • Page 22 marks CAPACITOR CC45SLlH070D Ceramic f0.5pF CC45SL1 H470K Ceramic 47pF C90-0262-05 Ceramic 0.047pF CS15ElC2R2M Tantalum 2.2pF 16WV CS15E1 VR22M Tantalum 0.22pF 35WV CE04WlHR47 Electrolytic 0.47pF 50WV C90-0254-05 Ceramic 0.022pF CE04WlA101 Electrolytic 100pF 10WV C90-0254-05 Ceramic 0.022pF CE04WlA101 Electrolytic 1OOpF IOWV C90-0262-05 Ceramic 0.047pF CK45D1 H 102M...
  • Page 23 :gks Description Parts No. marks Carbon 4.7kCl 1/8W CQ92M1 H223K Carbon 18kn 1/8W CK45F 1 H103Z Carbon 330n 1/8W CC45SL1 HOIOC Carbon lOkn 1/8W CK45D1 H102M Carbon 150n 1/8W CK45F1 H103Z Carbon 820n 1/8W CK45DlH102M Carbon 10kn 1/8W CC45SLlH221 CQ92MlH223K SEMICONDUCTOR CQ92MlH223K CK45DlH102M...
  • Page 24 Parts No. ,::is Description Parts No. CE04W1 A470 Electrolytic 47pF IOWV R 72 RD14CY2ElOlJ CK45F 1 HI032 Ceramic O.01pF +80%,-20% RD14CY2E102J CE04W1 H R47 Electrolytic 0.47pF 50WV RD14CY2ElOlJ CK45F1 HI032 Ceramic O.01pF +80%,-20% RD14CY2E102J CE04WlC100 Electrolytic 10pF 16WV R76, 77 RS14AB3AOIOJ CE04W1 H010 Electrolytic...

  • Page 26: Packing

    (H10-1206 (H25 0029 04)
  • Page 27 om-- Bind screw (N35-3006-45) Case (B) (~01-0704-12) Fig. Removing the Case REMOVING THE PANEL (Refer Fig. 7) Remove the knobs. --@. In fact, this board is Remove the screws constructed with Remove the panel and the subpanel Panel (A20-2301-05) Knob (SQU) (K21-0703-04) Knob (VOL) (K2 1-0704-04)
  • Page 28 + 6 0 0 00~~1~ -600 Front glass (810-0601-04) Fig. 8 Removing the Indicator REMOVING THE TX UNIT REMOVING THE FINAL SECTION (Refer Fig. (Refer Fig. Remove the leads @ and @from terminal pins. Rernove the leads from the terminal pins. 0-0.
  • Page 29 TO REMOVING LED MOTHER BOARD Remove knobs and front panel. Loosen SQIVOL control knob. Remove all LED display. Remove 4 screws on each corner of mother board J25-2513-03. Remove 2 connectors on board.

  • Page 30: Troubleshooting

    Normal Troubleshooting frequency at TP3 of VCO unit. Trouble in PLL circuit Condition Service Point Possible Cause Measures (Remedy) Checkvottage and replace trans- 5V supply at AVR circuit No 5V supply due to malfunc- former. (main body) tion in lClOl and 0101.
  • Page 31 Cause Remedy Symptom lmproper adjustment in protection circuit. TR defective in final driver stage. Abnormal voltage in AVR (2SD235). Check Improper adjustment for trimmer in pre-driver stage. Readjustment (3) Defective deflection at RF Antenna SWR defective. Check Readjustment meter (under normal power lmproper adjustment for VR1 in PA unit.
  • Page 32 Cause Squelch in ON setting. Tone switch set to tone squelch position. Malfunction in audio circuit. Speaker lead wires defective. (in particular, connecting parts). Ear phone jack broken. Antenna system defecitve (M-type connector, antenna wires, etc.) RF cavity tuning shifted. D6 defective in VCO unit.

  • Page 33: Level Diagram

    fc: 146.0 MHz...
  • Page 34 DISC 455 MHz 50 rnW easurernent polnt '& LOCAL OSC LEVEL (146 MHz) -0.7 0.9 V...
  • Page 35 PD UNlT 1x50-1380-10) (X54-1210-10)
  • Page 36 1.3 step 1-1 1. It should be stressed not to turn factory sealed parts. Set TR-7400A to 146.00 MHz simplex. Adjust VR1 on VCO to measure 9.00V at 9V terminal. Adjust TC1 inside metal box on VCO to read 5.00V at CV terminal.
  • Page 37 (1) Unlock circuit and its indicator. When TPI of VCO unit (X50-1370-10) is grounded with controls set arbitrarily. (a) The unlock indicator on the panel should light. (b) The RF voltage at TP2 of the RX unit (X55- 1150-10) should be attenuated by 20 dB or more. When the MHz control is turned rapidly, the un- lock indicator should go on and off.
  • Page 38 Dummy load " RF OUT Fig. 15 Sensitivity Adjustment Detector 2.5 Squelch Adjustment (1) Set the SOU knob at the I I-o'clock position and without receiving any signal, adjust VR2 of the RX unit so that reception noise just diminishes (by turn- ing it in the diminishing direction).
  • Page 39 3.3 Adjustment of MIX Stage (1) Connect the RF VTVM to TP3 of the TX unit and key the transmitter. Adjust Lll, L12, L13, L14, TCl and TC2 repeatedly for maximum indication. (2) Set the frequency to 144.5 MHz and adjust VR6l on the choke circuit board for maximum indication.
  • Page 40 switch to SQ, adjust VR3 of the RX unit so that DEV become +-I kHz. jig. Note: An active filter needed as a 3.10 Adjustment of Protection Circuit (1) Connect a DC voltmeter of 1 0.3 V range to terminal TP (on the filter circuit board). Adjust VR2 for minimum indication at a frequency of 146.0 MHz and the Hi setting.
  • Page 41 MIC INPUT LEVEL IN Example 2 ANTENNA INPUT VOLTAGE Example 3 RX S-METER SENSITIVITY a--144.00 x-~146.00 0-0147.99 10 pv 100 pv ANTENNA INPUT VOLTAGE...

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