Icom IC-751A Service Manual page 3

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TABLE OF CONTENTS
1. SPECIFICATIONS ................. 0c ccc ccc cee cee cree cnn eee e nett neste ees 1—1~2
1-1 GENERAL 0.00.00 cece cece cece cece cece cece eee nets eee e eee neeneteeteeseeeneeeenerenenes 1-1
1-2 TRANSMITTER 00.0.0... 0cccc ccc ce cece cece ccec eee ee eee e eee et ee eee etteeeneeneeeaes 1—1
1-3 RECEIVER oo... coc cccc cece cc cece cece eee eeece eee neta eee eee eeeneeeeteeetneteneeeetnneny 1-2
2 OUTSIDE AND INSIDE VIEWS ......0..0..0.00..0 cece cece eee c eee ete tee nene es 2—1~5
2-1 FRONT PANEL oo... 00.00 c ccc cece cca ccee eee eeeeece eee eeee been eeteeteeeeeetneeeeennes 2-1
2-2 DISPLAY... occ cee cece cece cece cece eect eee e eee e eee e tee net ete betneteet eet ee ence 2—2
2-3 TOP PANEL .......0..00cccccccce cece cce cee eee eea eee eeeeeteetneteeeteeenesteneeeeenes 2-2
2-4 REAR PANEL 2.0.0... 00.0cccecc nec eecc cee cee eect eee eee eeeeeeeeeeneeeeentteeeseneaes 2—2
2-5 MAINUNIT ........ccccccecc eee ec eee ee eee eee eee ece eee eseesteeneeeeeeeneaneeenerenes 2—3
2-6 LOGIC AND PLLUNITS .0..0..0..00ccc cece ees ce cece eee eee eee te nee eee eee eeenereereeenes 2—4
2-7 REUNIT ooo oc ccc cece cece cece cce eee ceeeeee eee eeeeeeeneteneteeeeteeeetereseneseeeeaes 2—5
2-8 PAUNIT ooo... ccccecceccc eee cece eee ecc eee ecesecee eee eeteeeteeeneeeeetneeteeeeeeeeeraes 2—5
3 BLOCK DIAGRAM 2.0.00... 00.00 ccc ccc cece cence cece cece eect eee eetbeeeeeeenies 3—1
4 CIRCUIT DESCRIPTION .................... 2c cece cee cnc ete ee cen eens 4—1~20
4-1. RECEIVER CIRCUITS 00.0.0... 000 cc cc ccc ccc ec cece eee e nett een eeeneseeeeeetenesneeaes 4—1
4-2 TRANSMITTER CIRCUITS .....0..0..00ccccceccceeeeeee cece cette eeeeetaeeseeteeeeies 4—4
4-3 POWER SUPPLY CIRCUITS ........0..00. ccc ccc eec cece ec eee eee et ee eee nee eeteee ner ee 4—8
4-4 PLU CIRCUITS 20.000... occ cc cece cece cece cece eee ee eect eeeeeteeeteeteeeieeeaeeeees 4—8
4-5 LOGIC UNIT 00... oo ccc e cece cece cece cece eee e eee neceeeeneeeneeneeeeeseeerneeeeeeeaes 4—12
4-6 DISPLAY UNIT 0.00... coc ccc cece ccc c cece nee ece neta eee eeceetneeteetteeeneteeereeeees 4—18
4-7 OTHERCIRCUITS 2.200.000. ccc ccc ec cece eee ee cece eee eee eee eee ee eeneeaeeneeeeeneee ened 4—19
5 DISASSEMBLY AND ASSEMBLY DIAGRAMS ...........................e sees 5—1~10
5-1 FRAME DISASSEMBLY .........0..00.00ccccccecee secu eeeeeceeeeeeeeeeteeeeeeeneneetaes 5—1
5-2 FRONT PANEL (1) DISASSEMBLY ...........00.00cccccceeeeeec eee eeeeeeeeeeeeeeenees 5—2
5-3 FRONT PANEL (2) DISASSEMBLY ...........0..00.000cceeceeeceeceeeeeeee eee eeeeeeees 5—3
5-4 FRONT PANEL (3) DISASSEMBLY ...........00.00cccccceeceeeeeeeeeeeeeeeeeeneeeeeeees 5—4
5-5 REAR PANEL DISASSEMBLY .........00..00c0cccccececee secu eecneeeeeeeesaeeceeneetees 5—5
5-6 FRONT UNIT CONNECTOR ASSEMBLY ........00..00c0ccceeecneceeeeeeeeeeeeteeeeeaes 5—6
5-7 MAINUNIT CONNECTOR ASSEMBLY .......0..00.000c0ecceeecneeeeeeeeeeeeeeeeeeeees 5—7
5-8 LOGIC AND PLL UNIT CONNECTOR ASSEMBLY .............00c00eceeeeeeceeeeeeeees 5—8
5-9 RF UNIT CONNECTOR ASSEMBLY .........000.00cc0cccceceeeee eee eseueeeeeeeeeneeenes 5—9
5-10 FILTER UNIT CONNECTOR ASSEMBLY ........00..00c00ccceeceeeeeeeeeeeeeee eee eeaes 5—9
5-11 REAR PANEL CONNECTOR ASSEMBLY ........00..00.00ccceeceeeeeeceeeeeee eee eeaes 5—10
6 MAINTENANCE AND ADJUSTMENT ..................0..-00.00:0ceceeeeeeee ees 6—1~9
6-1 PREPARATION BEFORE SERVICING ........0..00..0cccceceeecn eee eece eee eeeneeenetees 6—1
6-2 PLLADJUSTMENT 2000.0. cece cc cece ccc ecc cence cence eee e een ee ten eeeeeneeeeeneenee 6—2
6-3 FREQUENCY ADJUSTMENT ......0..00.000c cc cc ecec eee eceeeeeeeeeeeeeteeeeneteeenies 6—3
6-4 RECEIVER ADJUSTMENT .........0..00ccccc ccc ceeeeee eee eee eee eeeeteneeeeeterenies 6—4
6-5 TRANSMITTER ADJUSTMENT ........0..000c0ccceeceeeeeeeenecaeeeeeee een eteeerenenes 6—6
7 BOARD LAYOUTS 200.000.0000... 0 coco ccc cece ccc c eee e cence eee neeeeteneeaeeenes 7—1~9
7-1 FRONT AF UNIT 02000... 00.00 cc ccc cece cece cece ene ca ete eeee eect eee eeeteeneeeneeenetey 7—1
7-2 FRONT MARKER UNIT 0.2.00. 00.ccc ccc cc cece cece cece eeeeeeeeeee eee eee een eteneeneeey 7—1
7-3 FRONT MODE SWITCH UNIT 0.0.0... 00.. ccc cccc eee ee cence eee ete eet eeeeeeeeeeeeeees 7—1
7-4. MATRIX UNIT .00..0..00. 0000 ccc ecc cece eee cee cece nese eeeeeen seen eeeeeeeeeeeeteeeesees 7-2
7-5 MATRIX SWITCH UNIT 200.2... cece cece cece cece cece eee eeeeeeeeneeeeeeeeaeeeneerentens 7—2
7-6 DISPLAY UNIT ....0.. 00.00 cece ce ecc cece cece cece eee eeu eee eeeeeeeeaeeeeesteeieeeeeeaes 7—3
7-7 KEYER UNIT 200. ..c ccc cece ccc cece eee cece eceeecee bese ece een eeeetseeeneeeeeeeeeneeenes 7—3
7-8 LOGIC UNIT ooo. cc ccc cc cece cece ccc ce cee ee eee ee se eetbeeueeen eee eeeeeeeeeneeeneeaes 7-4
7-9 MAINUNIT 00.0... 0c cece ccc ce cece cece cece cece eeee eee ceed eceu een eeeeeeeeeeneeeeeneeaes 7—5
7-10 PLLUNIT oo... cece cece cece cece c cece eee ee eee cence eesti et eeeeeeeteeseeenereenees 7—5
THA REUNIT o.oo cece cece cece eee e cece bene eee cence eee eea een eenereeteereeeneenenees 7—6
7-12 PAUNIT ......0cccccc ccc ecceneeeeeee eet een ees ecb bee ebedeee bees eee nete been eeeeeeiees 7—7
7-13 PACONNECTOR UNIT ..0..0..0..0 cece ccc eec cence cece e ee eea eee eeeeteteeeeeenennenees 7—8
7-14 PACHOKE UNIT oo... .00.. 00. ccc ccc cece cece cence eee e cece nese eee netaeeeeeteeeeeeeeeey 7—8
7-15 FILTER UNIT 2... en nen rene nee enn e tenn eter neat ened 7—9