Kenwood TR-7850 Service Manual

® A product of
TRIO-KENWOOD CORPORATION
17-5, 2-chome, Shibuya, Shibuya-ku, Tokyo 150, Japan
TRIO-KENWOOO COMMUNICATIONS, INC.
1111. West Walnut Street, Compton, Califorma, 90220
TRIO-KENWOOO COMMUNICATIONS, GmbH
0-6374 Steinbach TS. Industriestrasse 8A. West Germany
S : TRIO-KENWOOO(AUSTRALIAIPT Y. LTD.
FRVI CE A N 1 A 30 Whiting Street. Artarmon. Sydney NSW. Australia 2064
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VHF FM TRANSCEIVER
USE THIS SERVICE MANUAL
TOGETHER WITH THAT OF TR-7800.
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CONTENTS
BLOCK DIAGRAM ......... ccc ccccece cette eee eee eeaeneee nen eenens 2
PC BOARD VIEW
FINAL UNIT (X45-1180-10) ........cc ccc ceeeeeeeeeeee teres 2
PARTS LIST 00... eccecceeeceeseseeccuusssaeseeuecesueseeneseaaes 3
SEMICONDUCTOR DATA ............cccccccccccsececseeeceseseeeeees 4
ADJUSTMENTS... ccccccccccecseeeseesssascsaseeusseneesanenees 5
SCHEMATIC ABBREVIATION. ............cccceccecneceseeeneeaeenes 6
SCHEMATIC DIAGRAM (K)(M) ........ eccetetttenereen 7
SCHEMATIC DIAGRAM (W)(T) .............06. BACK COVER
SPECIFICATIONS
[General] Frequency tolerance...............66 Less than +20 x 10° a
Semiconductors ...........0..c0ceeeees MPU 1 (—20°C~ +50°C) |
ICs 18 (W)(T), 19 (K)(M) Spurious radiation .................06. Hi Less than — 60 dB
Transistors 58 (W)(T), 60 (K)(M) LOW Less than — 53 dB
FETs 9 Maximum frequency
Diodes 79 (K)(M)(T), 78 (W) deviation (FM)............0:ccee +5 kHz
Frequency range.............ccseeee ees 144.000 to 145.995 MHz (W)(T) RPT. Tone burst frequency......... 1,750 Hz
144.000 to 148.995 MHz (K)(M) Microphone ...... ( e v eben eeeeeeenenenraes Dynamic microphone with PTT switch,
Frequency synthesizer............... Digital control, phase locked VCO 5002
Antennéimpedance.. 50 ohms [Receiver Section)
PODANCE «oe eeeeeeeerees m 4759 CIPCUITIY...... cece eee e ne ee ene ee eee re tees Double conversion superheterodyne
Power requirement Treereeeeeeeseeres 13.8V DC +15% Intermediate frequency ............. istIF 10.695 MHz
GrOUNGING ........ cece ce cee eee eens ences Negative , ondIF 455 kHz
* Operating temperature .............. 7 20°C to + 50°C ; ; Receiver sensitivity ...............6668 Better than 0.5 uV for 30 dB S/N
Current drain... eee eee 0.4A in receive mode with no input Better than 0.2 nV for 12 dB SINAD
signal 9A in Hi transmit mode (Approx.) Receiver selectivity ..............060 More than 12 kHz (—6 dB)
nes than sm or memory pack up Less than 24 kHz (—60 dB)
rom an external power supply Spurious response ...............0006. Better than 60 dB
through the BACK UP terminal) Squelch sensitivity ...............0006. 0.16 uV (threshold) |
| Less than 2 mA for memory back up Auto scan stop level.............0008. Less than 0.2 nV (threshold)
. . (from battery) WY Audio OUtPUt.............c cece cece ee eens More than 2.0 watts across 8 ohm
DiIMENSIONS.............0ccccc eee eee eens 175 mm (6-7/8") wide load (10% dist.)
64 mm (2-1/2") high
220 mm (8-5/8") deep
(projections excluded)
WeIGHt .......ccccceeeeeeceeeeeeeeeene eee 2.2 kg (4.84 Ibs) (approx.)
[Transmitter Section]
RF output power
(at 13.8V DC, 502 load) ..... Leese HI 40 Watts min.
LOW 1 to 15 watts approx.
(According to FREQ.)
Modulation ..........0cccccccceeeeee eee Variable reactance direct shift
Note: Circuit and ratings are subject to change without notice
due to developments in technology.
© 1981-4 PRINTED IN JAPAN
B51-0936-00 (K)(M)(W)(T) 1000 @