Sua chua TV

7/31/2019 Sua chua TV

1/39


2/39

[email protected]

trng => bc nh ny mang thng tin v chi, sau ta dng mu t => cho ta sc mu , ta t mu tht m cho ta bo ho mu cao, nu t mu nht th bo ho mu thp.

Truyn hnh en trng ch truyn i thng tin v chi, cn truyn hnh mu th truyn y cc thng tin ca nh.

b) nhy tng phn .Mt bc nh c nhiu chi tit nh v cc chi tit nh c chi khc nhau, tng phn l tl gia chi cao nht so vi chi thp nht, t l ny cng ln th tng phn cng cao,ngoi t nhin th chnh lch ny l khong 10.000 ln nhng trong truyn hnh (Ti vi) th thay i ny l khong trn 100 ln, trong mn hnh my tnh th thay i l 256 ln.

nh c tng phn cao nh c tng phn thp

Mt ngi c kh nng phn bit c hai im sng c tng phn hn km nhau khong0,02 ln.

c) Kh nng phn gii ca mt . l kh nng mt ngi phn bit c hai im ring bit khi nhn

t mt gc hp.

Mt ngi nhn hai im A, B theo mt gc hp

Mt ngi ch c kh nng phn bit c hai im A, B trn khi nhn t mt gc > 1,5' , nugc < 1,5' th mt ngi khng c kh nng phn bit c hai im ring r, da vo c im ny trontruyn hnh ngi ta ch pht li cc im nh ri rc sao cho t mt ngi nhn vo cc im nh vi mtgc nhn nh ta khng thy c l hai im phn bit.

=> T nghin cu trn ngi ta tnh c trn mt mn hnh, ngi ta khng cn pht li tt c cc imnh m ngi ta ch pht li khong 600 im nh theo chiu dc v 800 im nh theo chiu ngang, mnhnh c phn gii cng cao th s im nh cng ln.

d) Qun tnh ca mt .Khi ta nhn mt bc nh, nu bc nh vt tt th hnh nh vn tn ti trong con ngi khong 0,1


3/39

[email protected]

giy, l hin tng lu nh trong vng mc hay cn gi l qun tnh ca mt.=> Li dng tnh cht ny, nu ta cho bc nh xut hin ri rc khong 10 ln trong 1 giy th ta c cm

nhn l mt bc nh lin tc.=> Trong truyn hnh, ngi ta truyn i 25 bc hnh / giy, do hnh nh ta cm nhn l lin tc.Th d di y cho thy cng mt bc nh nhng c cc tc xut hin khc nhau :

nh xut hin 1 ln / giy nh xut hin 5 ln / giy

2. Nguyn l truyn hnh.

* Cc tham s ca hnh nh .

chi trung bnh : Mi im nh u c chi ring cu thnh ton b nh, trongtruyn hnh en trng ngi ta truyn i tn hiu c trng cho chi ca mi im nh.

Mu sc : Mu sc ca cc phn t nh, tham s ny ch cn thit vi truyn hnh mu. Hnh phng : Truyn hnh l truyn bc hnh phng theo khng gian hai chiu, truyn

tng im nh ln lt theo chiu ngang v chiu dc, chiu ngang gi l qut dng,chiu dc gi l qut mnh.

nh ng Truyn hnh l truyn i cc bc nh ng , mt ngi cm nhn schuyn ng l lin tc th cn truyn i s bc nh sao cho mt khng thy c snhp nhy ca nh.- Th d bc nh IC trn c tc l 5 hnh / giy, ta cm thy hnh nhp nhy, nhngnu ta tng ln ti 25 hnh/ giy th ta s thy bc nh l lin tc.

* Nguyn l truyn hnh nh .Ngi ta khng truyn ton b bc hnh m truyn ln lt tng dng t trn xung di nh

ta c mt quyn sch.Mt bc hnh c chia lm 625 dng qut t trn xung di, sau truyn i tn hiu ca

tng dng qut n my thu vi tc 15625 dng / giy, my thu ti to li c hnh nhc th cng phi qut li 625 dng cho mt mn nh v cng phi qut vi tn s 15625 dng /giy, qu trnh ny gi l ng b gia tn hiu thu v pht.

* Nguyn l qut .


4/39

[email protected]

Nguyn l qut nh.

Bc nh trn minh ho c qut vi tc 10 dng / giy v ch qut c 8 dng cho mlt t trn xung di, trong truyn hnh cng c nguyn l qut tng t nhng c tc qut l 15625 dng/ giy, v qut 312,5 dng cho mt lt t trn xung (mt bc hnhchia lm 625 dng v c qut lm hai lt, mt lt qut cc dng chn v mt lt

qut cc dng l )

3. Tn hiu truyn hnh.

* S to thnh tn hiu th tn ( Video ) .

Camera i hnh nh thnh tn hiu Video

truyn hnh nh i xa trc tin hnh nh phi c i thnh tn hiu in - gi l tn hiuVideo , hnh nh c thu vo qua ng knh v hi t trn mt lp phin c bit, sau ta dngnguyn l qut chuyn t thng tin hnh nh thnh tn hiu in.


5/39

[email protected]

Dng tia in t qut trn lp phin to thnh tn hiu Video

Lp phin l mt mng kim loi c bit c in tr thay i theo cng sng, khi c in t qut qua, cc im sng ti c tr khng khc nhau to thnh dng in mnh yukhc nhau i qua, tn hiu in ly ra t lp phim c dng in bin i t l vi thng tinv sng ca hnh

nh, tn hiu ny c a vo mch iu ch to thnh tn hiu Video ng ra ca Camera.

* Thnh phn ca tn hiu truyn hnh y

Tn hiu truyn hnh y bao gm tn hiu th tn (mu xanh), xung ng b dng (mu ),

xung ng b mnh ( mu tm)

Thi gian qut thun t t1 n t2 l 54s Thi gian qut ngc dng t t2 n t3 l 10s Thi gian qut ngc mnh t t4 n t5 l 25s


6/39

[email protected]

Xung ng b dng v mnh c chn vo tn hiu video trong thi gian tia in t qutngc.

Tia qut ngc dng mu tm, tia qut ngc mnhmu xanh l , tia qut dng thun l tia mu trng

Tn hiu truyn hnh y bao gm : Tn hiu th tn : thu c t nguyn l qut nh nh trn cn gi l tn hiu video

( on tn hiu t t1 n t2 ) Xung ng b dng H.Syn (Horyontal Synsep : ng b dng): l xung chn vo tn

hiu video trong thi gian tia in t qut ngc (on t2 n t3 ) xung ny c giisang my thu ng b tn s qut dng.

Xung ng b mnh V.Syn (Vertical Synsep) l xung chn vo tn hiu Video khi qutxong mt mn hnh t trn xung di (on t4 n t5) xung ny c gi sang my thu ng b tn s qut mnh.

4. iu ch tn hiu pht i truyn hnh .

Tn hiu ting c gii tn t 20Hz n 20KHz rt hp so vi ton b di tn ca tn hiu hnh t0 n 6MHz , v vy bo ton tn hiu ting khi pht chung vi tn hiu hnh, ngi ta phi iuch tn hiu ting vo sng mang tn s t 4,5MHz n 6,5MHz theo phng php iu tnthnh sng FM ri mi trn vi tn hiu hnh to thnh tn hiu video tng hp .

iu ch tn s tn hiu ting


7/39

[email protected]

Nh vy tn hiu video tng hp bao gm (Video + H.syn + V.syn + FM) pht ton b tn hiu ny i xa, i pht ngi ta tin hnh iu ch tn hiu video tng

hp trn vo tn s siu cao tn di VHF t 48MHz n 230MHz hoc di UHF t 400MHz n880MHz theo phng php iu bin. v chia lm nhiu knh, mi knh chim mt gii tnkhong 8MHz.

Ph tn hiu ca mt knh truyn hnh.

Nguyn l pht ca i truyn hnh.

Sau khi tn hiu Video tng hp c iu ch vo mt knh sng : Th d knh 9 (nm ph tn hiu t 199,25MHz n 205,75MHz) ta c sng mang , sng mang tip tc khuch i cng xut hng chc KW ri a ra Anten pht pht thnh sng in ttruyn i trong khng gian vi vn tc nh sng.


8/39

[email protected]

Phn tch s khi My thu hnhNi dung : Phn tch s khi ca my thu hnh en trng, M t s hot ng ca i

truyn hnh

1. S khi Ti vi en trng.

S khi my thu hnh en trng .

My thu hnh en trng l hi t tt c nhng kin thc c bn ca k thut truyn hnh, hiumy thu hnh en trng l c s tip cn vi my thu hnh mu v my thu hnh k thut s.

My thu hnh en trng bao gm cc khi chnh sau :

B knh : C nhim v thu tn hiu sng mang t cc i pht sau i tn v tn

hiu IF, cung cp cho mch khuch i trung tn. Khi trung tn : Khuch i tn hiu trung tn v tch sng th tn tch tn hiu

Video tng hp ra khi sng mang , tn hiu thu c sau tch sng gm c tn hiuVideo, xung H.syn, xung V.syn v tn hiu FM.

Tng khuch i th tn: T tn hiu Video tng hp, tn hiu

video c tch ra i vo tng khuch i th tn, tng K th tn khuch i tn hiuvideo ln bin mnh ri a vo Katt n hnh iu khin dng pht x, tito li hnh nh trn mn hnh.

n hnh : Chuyn i tn hiu truyn hnh thnh hnh nh quang hc, khi phc li

nh ging pha pht. Khi ng b : Hai xung ng b c gi sang my thu t pha pht c nhim viu khin khi qut dng v qut mnh ca my thu qut cng tn s nh bn pht khi phc li hnh nh, hai xung ny c tch ra sau tch sng th tn v ckhuch i qua khi ng b, sau xung H.syn i ti iu khin mch dao ng dng,xung V.syn i ti iu khin mch dao ng mnh.


9/39

[email protected]

Khi qut dng : Nhim v ca khi qut dng l to ra cc mc in p cao cungco cho n hnh hot ng, ng thi cung cp xung dng cho cun li ngang litia in t qut theo chiu ngang.

Khi qut mnh : Nhim v ca khi qut mnh l to ra xung mnh cung cp chocun li tia, li tia in t dn theo chiu dc

Khi ng ting : Khuch i tn hiu iu tn FM, sau tch sng iu tn lyra tn hiu m tn v khuch i qua tng cng xut ri a ra loa.

M t s hot ng ca i truyn hnh

Bui truyn hnh trc tip Cat Singer


10/39

[email protected]

B knh v hin tng hng knhNi dung : Nhim v, Cu to v nguyn l hot ng ca b knh, Mch cng hng cao

tn, dao ng ni, mch i tn trong b knh, Phn tch h hng ca b knh v phngphp kim tra sa cha.

1. S khi ca b knh.

S khi ca b knh

Mch vo : C nhim v chn knh theo nguyn l cng hng sng, ti anten cnhiu sng mang t cc i pht khc nhau i ti, sng mang no c tn s trng vitn s dao ng ca mch vo s c chn i vo mch khuch i.cao tn.

Mch K cao tn : Khuch i sng mang t i pht sau khi c thu vo qua mchcng hng .

Mch dao ng : C nhim v to dao ng ni a vo mch trn tn. Mch trn tn : C nhim v trn tn s dao ng vi tn hiu cao tn ly ra tn s

trung tn IF

IF = F0 - RF

F0 : L tn s dao ng ni

RF : L tn hiu cao tn ( sng mang )IF : L tn s trung tn, tn s IF c

di tn c nh t 31,5MHz n 38MHz

2. Mch vo & K. i cao tn.

Mch vo thc cht l mt by cng hng, khi ta chuyn knh, cc cun dy c cm khngkhc nhau c tip xc vo mch cng hng lm thay i tn s cng hng, nu tn scng hng trng vi tn s sng mang th tn hiu sng mang c thu vo v c khuchi qua tng Q1 , u ra tng K cao tn Q1 c thm mt mch cng hng na nng bin tn hiu ln mc cao nht.


11/39

[email protected]

B chuyn knh c kh trong my thu hnh en trng.

3. Mch dao ng ni

Mch to dao ng

Mch to dao ng cung cp dao ng ni cho mch i tn, khi ta chuyn knh, cun L1c thay th to ra mch cng hng c tn s thay i

4. Mch i tn


12/39

[email protected]

Mch i tn

Mch i tn c tn hiu RF v tn s dao ng ni OSC cng c a vo cc B ca ni tn, tn hiu trung tn IF ly ra trn cc C c gi tr bng hiu hai tn s u vo

IF = OSC RF

Nu tn s RF tng th tn s dao ng OSC cng tng tng ng m bo tn s IF lunlun khng i, tn s trung tn IF chim mt gii tn t 31,5MHz n 38MHz

Gii tn ca tn hiu IF

5. Hin tng khi hng b knh

Khi hng b knh ta thy mn hnh c cc biu hin nh sau :

Bnh 1 ) Mn nh ch c nhiu, khng c hnh.


13/39

[email protected]

Mn nh c nhiu, khng c hnh.

Phn tch nguyn nhn : Nhiu bt ngun t mch khuch i trung tn, mn nh c nhiuchng t t mch khuch i trung tn cho ti n hnh hot ng tt, khng c hnh tc lkhng thu c tn hiu t i pht => Suy ra hin tng ny l do hng b knh hoc t

Anten.

Hng sa cha :

Kim tra in p Vcc cho b knh Kim tra in p t iu khuch AGC c khong 6V Kim tra Anten Cc yu t trn tt th ta thay th b knh.

Bnh 2 ) Mn nh c hnh nhng rt nhiu, ting r

Mn nh c hnh nhng rt nhiu ting r.

Nguyn nhn ca hin tng trn hon ton tng t nh bnh 1, nhng mc hngnh hn, cc bc kim tra v sa cha tng t Bnh 1


14/39

[email protected]

Mch khuch i trung tn IFNi dung : Phn tch s nguyn l ca mch khuch i trung tn v mch tch sng th

tn, hin tng khi hng trung tn v cc bc kim tra sa cha

1. S mch khuch i trung tn

Mch khuch i trung tn s dng IC

IC Khuch i trung tn bao gm cc mch .

IF AMPLY l mch khuch i tn hiu trung tn t b knh a sang, sau cung cptn hiu cho mch tch sng.

Detector L mch tch sng, tch tn hiu Video tng hp ra khi sng mang ca ipht, bin p T2 cng hng cho mch tch sng.

Vdeo Amply L mch khuch i tn hiu Video trc khi a ra ngoi

IF AGC (Auto Gain Control ) L mch to in p t iu chnh khuch i cho mchtrung tn

RF AGC L mch to in p t iu chnh khuch i cho mch RF Amply ca bknh

Mch trung gian gia b knh v tng khuch i trung tn l b lc gii thng, mchny c nhim v cho tn hiu trung tn thuc gii 31,5MHz n 38MHz i qua v loi bcc tn s ln cn, mch ny bao gm cc linh kin, C1,L1,C2,C3, L2, T1 to thnh ccmch cng hng nng cao bin tn hiu trong di sng trung tn, tn hiu voc a vo cc chn 8 v 9 ca IC

Tn hiu ra chn s 3 l tn hiu Video tng hp bao gm Tn hiu th tn (Video),xung H.syn, xung V.syn, tn hiu iu tn FM.


15/39

[email protected]

Cc thnh phn trong tn hiu Video tng hp

2. Biu hin khi hng trung tn.

Trung tn l ngun sinh ra nhiu trn mn hnh ng thi cng l mch khuch i tn hiu thut b knh, v vy khi hng trung tn mn hnh thng c biu hin khng c nhiu, khng chnh, khng c ting, ch cn mn nh sng min .

Ti vi hng trung tn, ch cn mn sng mn, khng c nhiu.

3. Cc bc sa cha mch trung tn.

Xc nh ng nguyn nhn l h hng mch trung tn : da vo biu hin nh trn ,mn nh sng mn khng c nhiu, khng

c hnh, khng c ting. Xc nh v tr ca mch trung tn trn v my : L khu vc c cc bin p cng hng

trung tn bng hp st vung c li ferit chnh c Kim tra ngun nui Vcc 12V cho IC : in p ny o trn t ho lc ngun cnh IC

Thay IC trung tn


16/39

[email protected]

Khi khuch i th tn VideoNi dung : Nhim v ca mch khuch i th tn, phn tch s mch khuch i th tn,

Phn tch h hng v phng php kim tra sa cha

1. Tn khuch i th tn (Video)

Nhim v ca mch khuch i th tn :

Khuch i tn hiu Video sau tch sng ln bin ln => cung cp cho n hnhti to li hnh nh.

Tip nhn xung dng v xung mnh a v xo tia qut ngc Thc hin cc chc nng iu chnh tng phn, sng.

Tng khuch i th tn my Samsung 359R

Nhim v cc linh kin trong mch :

C1 : L t ni tng

CF1 : L thch anh, lc tn hiu ting khng cho ting nh hng sang ng hnh n Q khuch i tn hiu th tn, R2 l in tr nh thin, R3 l tr ghnh, R4 l trn nh nhit , R5 l in tr phn p.

Trit p Contras iu chnh bin tn hiu ra => L trit p chnh tng phn trnmn hnh

Xung dng H.P (Horyontal Pull ) i qua R6 v D1, xung mnh V.B (Vert Blanking) iqua R7 v D2 : hai xung cng i qua t C3 vo cc E n K th tn lm nhim v xotia qut ngc


17/39

[email protected]

T C4 a tn hiu th tn vo Katt n hnh v ngn in p mt chiu Trit p Bright lm thay i in p mt chiu trn Katt => L trit p chnh sng

mn hnh

Phn tch cc h hng ca tng khuch i th tn :

1) Trng hp tng khuch i th tn khng hot ng:n K th tn khng hot ng khi

Mt ngun Vcc 110V Hng n K th tn t in tr nh thin t in tr ghnh

Biu hin trn mn hnh l: Mn nh ch c mn sng mn , khng hnh, c tia qutngc.

Biu hin khi hng tng khuch i th tn

Phng php kim tra tng khuch i th tn :

Kim tra ngun Vcc cho tng khuch i th tn phi c 110V Kim tra ch in p trn n Q phi c UBE 0,6V v UCE 2/3 Vcc 70V

2) C hnh nhng c tia qut ngc xen vo

C hnh : Chng t tng K th tn vn hot ng bnh thngC tia qut ngc: L do mt xung mnh a v n K th tn xo tia qut

ngc.=> Cn kim tra mch a xung mnh t cng xut mnh v tng K th tn kim tra


18/39

[email protected]

Cu to v hot ng ca n hnhNi dung : Tm hiu cu to ca n hnh en trng, Nguyn tc hot ng ca n hnh, Hintng ca n hnh gi, n hnh hng

1. Cu to v hot ng ca n hnh

Cu to v hot ng ca n hnh

Cu to ca n hnh :n hnh l mt bu thu tinh ht chn khng v c cc cc chnh l :

Cc Ant : c cung cp in p HV ( Height Vol : 10KV ) to ra sc ht cc tiain t bay v m hnh.

Katt : L cc pht x ra dng tia in t bay v pha mn hnh, tia in t bt rakhi b mt Katt th Katt phi c nung nng nh si t, Tn hiu th tn c avo Katt iu khin dng tia in t pht x, ti to li hnh nh trn mn hnh .

Li G1 cn gi l li khin c u Mass, khi tt my G1 c cung cp in p-100V chn li tia in t cn d trn n hnh, trnh hin tng xut hin msng khi tt my.

Li G2 gi l li gia tc : c cung cp in p +110V tng tc tia in t Mn hnh : c ph mt lp Phospho ng nht, khi c tia in t bn vo th lp

Phospho pht sng, cng sng t l vi cng dng tia in t. Cun li tia : Nm ngoi c n hnh, gm hai cun li dng v li mnh, c nhim v

li tia in t qut t tri sang phi, t trn xung di, nu khng c hai cun li tiath tia in t i thng v pht sng thnh mt im trn mn hnh.


19/39

[email protected]

Hot ng ca n hnh : n hnh hot ng ( cho hnh nh ) trc ht ta cn phncc cho n hnh sng ln , sau a tn hiu th tn vo Katt iu khin dng tia in tpht x to li hnh nh .

n hnh pht sng th ta cn cung cp cho n hnh 4 iu kin sau :

C in p HV = 10KV cung cp cho Ant C in p 110V cung cp cho li G2 C in p 12V cung cp cho si t Katt c thot xung mass

2. H hng thng gp ca n hnh :

n hnh thng hng dng tia pht x b yu i , lm cho sng mn hnh gim hocmt nh sng.

Kim tra n hnh : kim tra n hnh, ngi ta kim tra ccin p phn cc cho n hnh, nu cc in

p ny vn y m n hnh khng sng => l n hnh hng, nu mn hnh sng yu=> l mn hnh b gi.


20/39

[email protected]

Khi qut dng v cao pNi dung : Nhim v ca khi qut dng, phn tch s khi qut dng, H hng thng gp

ca khi qut dng, nguyn nhn v phng php kim tra sa cha

1. Nhim v ca khi qut dng

Nhim v chnh ca khi qut dng l to ra cc mmc in p cao phn cc cho n hnhhot ng, ngoi ra khi qut dng cn cung cp xung dng cho cun li ngang li tia int qut theo chiu ngang mn hnh.

2. Phn tch s khi qut dng .

S khi ca khi qut dng

Mch so pha : So snh gia hai tn s l xung H.syn t i pht gi ti vi xung AFCt cao p hi tip v to ra in p iu khin, nu tn s AFC bng H.syn th piu khin khng i => tn s qut dng khng i, nu tn s AFC > tn s H.Syn thmch so pha to ra in p iu khin gim => lm tn s dao ng dng gim v

ngc li. ( AFC l vit tt ca Auto Frequency Control : T ng iu chnh tn sdng, H.syn l vit tt ca Horyontal Synsep : Xung ng b dng )

Mch to dao ng dng : To ra xung dng c tn s bng 15625Hz , tn s ny cgi c nh nh in p iu khin t mch so pha, trng hp hng mch so pha hocmt xung H.syn

hay xung AFC th tn s dng bi sai => sinh hin tng mt ng b => nh b xinhoc tri ngang.

Tng kch dng : khuch i xung dng cho mnh sau a ti iu khin ncng xut ng m

Tng cng xut : Hot ng ch ngt m iu khin bin th cao p hotng . B cao p : L bin th hot ng tn s cao 15625Hz cung cp cc mc in p

cao cho n hnh, nh p HV = 10.000V, p G2 = 110V, v cung cp xung dng iukhin cun li ngang.

3. S chi tit khi qut dng my Samsung 359R


21/39

[email protected]

S khi qut dng my Samsung 359R

Phn tch s chi tit :

R1, R2, D1, C1 l mch so pha, mch ny so snh xung H.syn v xung AFC ( mu tm) to ra in p iu khin i qua R3 v R4 vo iu khin n dao ng Q1 R3, C2 l mch lc tch phn loi b thnh phn xung xoay chiu , gi li thnh phn

mt chiu Q1 l n to dao ng, t C4 v cun L1 to thnh mch dao ng LC, t C3 hi tip

dng, tn s dao ng ph thuc vo cc t C3, C4, v cun dy L1, nm chnhH.Hold chnh l iu chnh li cun dy L1 => lm cm khng L1 thay i => lm tn s


22/39

[email protected]

dao ng thay i, tn s c n nh nh in p iu khin t mch so pha asang , dao ng c ly trn chn E i qua R8 a sang tng kch dng.

Q2 l n kch dng, khuch i xung dng ln mnh sau ghp qua bin p kchT1 sang iu khin n cng xut Q3

Q3 l n cng xut, hot ng ngt m nh mt cng tc in t => to ra dng in

xoay chiu chy qua cao p T2, t C5 l t b, C6 v D3 l t v Diode nht, D4 v C7l mch chnh lu in p B2 =110V cung cp cho G2, C8 v D5 to ra in p m avo G1 khi tt my, in p HV ly trn cun th cp khong 10KV in p ny dngv n hnh lm cc m ca t lc v vy v n hnh phi lun lun c tip mass .

Tng dao ng dng 4. H hng thng gp ca khi qut dng.

1) My c vo in nhng khng ln mn sng .

My c vo in nhng khng ln mn sng


23/39

[email protected]

Nguyn nhn : C hai nguyn nhn dn n hin tng trn l

Hng khi qut dng => cao p khng hot ng Hng n hnh.

Kim tra : Kim tra in p B2 ( o p B2 trn t C7 bng 110V ) xc nh xem cao p c hot

ng hay khng ? nu p B2 = 0V l cao p khng hot ng . Kim tra in p cung cp cho cc tng cng xut, tng kch, tng dao ng xem c

khng ? o ch in p UBE v UCE trn cc n Q1 v Q2, thng thng in p ny c

UBE 0,6V v UCE 2/3 Vcc

2) Mt ng b dng, hnh nh b hnh sc da

Hnh nh b hnh sc da do mt ng b dng

Nguyn nhn : Hin tng trn l do sai tn s dng c th do hng

Hng mch so pha Mt xung ng b H.syn t mch tch xung ng b a sang mch so pha Mt xung AFC t cao p a v so pha Chnh sai nm H.Hold

Kim tra :

Chnh li trit p H.Hold ( trit p chnh dao ng dng ) Kim tra cc linh kin trong mch so pha R1, R2, D1, C1 Kim tra mch cung cp xung ng b H.syn

Kim tra t , tr dn xung dng AFC v mch so pha


24/39

[email protected]

Khi qut mn hinhNi dung : Nhim v ca khi qut mnh, Phn tch s khi, Phn tch cc h hng vphng php kim tra sa cha khi qut mnh

1. Nhim v ca khi qut mnh :

Nhim v ca khi qut mnh l li tia in t qut theo chiu dc, khi qut mnh bao gm :

Mch to dao ng : To ra xung mnh c tn s 50Hz cung co cho tng cng xut Mch tin K: Khuch i xung mnh cho kho hn trc khi a vo tng cng

xut. Tng cng xut : Khuch i xung mnh cho ln ri a n cun li mnh li

tia tia in t dn theo chiu dc. Xung ng b : iu khin cho mch dao ng , dao ng ng tn s.

S khi - khi qut mnh.

2. S chi tit khi qut mnh s dng n bn dn :

S chi tit khi qut mnh dng n bn dn.

Phn tch s mch :


25/39

[email protected]

Q1 l tng dao ng, hot ng theo nguyn l dao ng nght, L1 l cun dy to daong, VR1 l trit p iu chnh tn s cn gi l trit p V.Hold

VR2 l trit p a xung dao ng sang tng tin Ki, khi chnh VR2 s lm thay ibin dao ng ra => VR2 l trit p chnh chiu cao mn hnh.

VR3 l trit p chnh tuyn tnh, khi chnh VR3 th dng xung thay i => tuyn tnh

mnh thay i, tuyn tnh l dn u gia cc im nh theo chiu dc. Q2 l tng tin khuch i , K o pha tn hiu trc khi a vo hai n cng xut. Q3 v Q4 l hai n Ki cng xut, mc theo kiu y ko L2 l cun li mnh gn trn c n hnh Mch hi tip qua C1 c tc dng sa mo tuyn tnh . Xung ng b mnh c a vo mt u ca cun dy L1

3. S khi qut mnh dng IC trong Ti vi Samsung 359R

S khi qut mnh dng IC trong Ti vi Samsung 359R

Phn tch s trn :

Trong IC c tch hp ba mch : To dao ng : V.OSC, tng tin Ki V.Amplyv tng cng xut V.OUT, cc linh kin in tr, t in c a ra ngoi.

Xung ng b V.SYN i qua mch lc tch phn R1, C1 sau i qua t vo chn s 5=> i vo mch dao ng gim c nh tn s mnh.

Trit p V.HOLD chn 6 c tc dng iu chnh thay i tn s mnh. Trit p V.SIZE chn 4 c tc dng iu chnh thay i kch thc dc mn hnh.


26/39

[email protected]

Trit p V.LIN t sau cun li tia c tc dng thay i in p hi tip => Lm thay ituyn tnh dc mn hnh, C3, C4 l cc t hi tip .

4. Cc h hng thng gp ca khi qut mnh.

1) Mn hnh ch cn mt vch sng ngang

Mn nh cn mt vch sng ngang

Nguyn nhn :

Mt in p cung cp cho khi qut mnh Hng IC cng xut mnh Hng cc linh kin R, C xung quanh IC

Kim tra :

Xc nh ng IC cng xut mnh ( d ngc t zc li mnh v ) Kim tra Vcc cho IC ( vi my en trng l 12V vi Ti vi mu l 24V) o Vcc trn t lc

ngun to nht cnh IC Thay IC cng xut mnh nu cc ch in p c .

2) Mn nh b mo tuyn tnh dc, co di chn, dn trn u :


27/39

[email protected]

Mn nh b mo tuyn tnh dc

Nguyn nhn :

Chnh sai trit p V.LIN Kh cc t ho trn mch hi tip sa mo tuyn tnh. Hng IC

Khc phc :

Chnh li trit p V.LIN Thay cc t ca mch hi tip nh t C3, C4 s trn ( Cc t hi tip l t ho

thng c tr s nh t 1F n 22F nm xung quanh khu vc IC cng xut mnh.) Thay IC nu cc nguyn nhn trn c loi tr .

3) Hnh b tri theo chiu dc

nh b tri theo chiu dc

Nguyn nhn :

Chnh sai trit p V.Hold => lm sai tn s dao ng mnh. Mt xung ng b V.SYN


28/39


29/39

[email protected]

Khi khuch ai xung ng b

Ni dung : Nhim v ca cc xung ng b, phn tch s mch khuch i v tch xung ngb, cc h hng ca khi ng b.

1. Mch khuch i v tch xung ng b

Xung ng b bao gm xung ng b dng H.SYN v xung ng b mnh V.SYN c gisang my thu hnh cng vi tn hiu Video, hai xung ng b ny c nhim v iu khin khiqut dng v qut mnh qut ng tn s nh bn pht, iu ny rt quan trng cho vic khiphc li hnh nh, nu bn my thu b sai tn s qut dng s sinh mt ng b dng => hnh b xin, nu sai tn s qut mnh s sinh mt ng b mnh => hnh b tri theo chiu dc.

S khi ca khi ng b :

S khi ca khi ng b

Mch tch xung ng b : Tch tn hiu ng b chung ra khi tn hiu Video tnghp . Mch khuch i : Khuch i bin xung ng b chung Mch tch phn : Cho tn hiu ng b mnh V.SYN i qua Mch vi phn : Cho tn hiu ng b dng H.SYN i qua

S mch chi tit :


30/39


31/39


32/39


33/39


34/39


35/39

[email protected]

My khng mn sng, khng hnh, khng vo in

Nguyn nhn :

Chy bin p ngun, hoc t cu ch. Chy cc Diode ca mch chnh lu

Kim tra :

Kim tra bin p ngun : ng h thanh x1 v o vo hai u phch cm in AC,nu kim ng h khng ln => l bin p ngun b chy, nu kim ln vi chc ohm lbin p bnh thng.

o kim tra trn cc Diode chnh lu cu Cui cng ta cp in v o trn hai u t lc ngun chnh phi c 18V DC

2) Hnh nh b un o, c ting loa .

Hnh nh b un o

Nguyn nhn :

Bn cht ca hin tng trn l do in p cung cp cho my b nhim xoay chiu 50Hzv vy nguyn nhn l :


36/39


37/39

[email protected]

Khi ng tingNi dung : Phn tch s khi ng ting, phn tch mch trung tn ting, phn tch h

hng thng gp v phng php kim tra sa cha

1. S khi ng ting

S khi ng ting

Tn hiu iu tn FM i cng tn hiu Video tng hp c tch qua t giy => i qua mchcng hng u vo i vo tng khuch i trung tn ting => sau khi K ln bin ln tnhiu a sang mch tch sng iu tn ly ra tn hiu m tn => sau tn hiu m tnc khuch i qua mch cng xut ri a ra loa pht li m thanh.

2. Mch trung tn ting dng Transistor

Mch trung tn ting dng Transistor

T301 l bin p trung tn cng hng u vo , cng hng tn s 6,5MHz Q1 l n khuch i trung tn T302 l bin p trung tn tch sng, sau bin p T302 l mch tch sng iu tn n Q2 l mch khuch i tn hiu m tn .

3. Khi ng ting dng IC


38/39

[email protected]

Khi ng ting trong Tivi Samsung 359R

CF1 l thch anh cng hng u vo, cng hng tn s 6,5MHz IF Amply l tng K trung tn ting FM DET l mch tch sng iu tn CF2 l thch anh cng hng u ra Tn hiu m tn sau tch sng c a n trit p Volume sau a sang tng

cng xut AUDIO OUT khuch i v a ra loa.

4. Hin tng h hng khi ng ting

1) My c hnh, khng c ting.

Nguyn nhn :

Hng loa Mt in p Vcc cung cp cho khi ng ting

Hng IC cng xut ting

Hng mch trung tn ting

Kim tra :

Kim tra loa : ng h thang x1 o vo hai u dy loa, nu c m thanh stsot loa l loa bnh thng, nu kim khng ln v khng c ting ng l loa hng.

o kim tra Vcc cho IC cng xut Thay IC ting nu cc iu kin trn tt.

2) C ting r km theo ting ni , ting ni nh.

Nguyn nhn :


39/39

[email protected]

Do mch trung tn cng hng sai tn s, thch anh cng hng khng ng h .

Kim tra :

Kim tra mch trung tn, kim tra cc thch anh cng hng, nu thu cc i trong nc

th thch anh l 6,5MHz.

Sua chua TV

Documents

Transcript of Sua chua TV