Tong Hop Truyen Hinh

7/30/2019 Tong Hop Truyen Hinh

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I. Nguyn l truyn hnh mu

Trong h thng truyn hnh en trng nh truyn i c hin th bng sng ti cc im

tng dng my nh, camera c nhim v bin i sng ti truyn hnh nh nhiu mc in p

khc nhau. m bo cho nh thu c ng b vi nh pht i, ta cn phi pht xung ng b

dng v xung ng b mnh. Dng sng ca tn hiu truyn hnh en trng y gm tn hiu h

xung xa v xung ng b, v vy trong h thng truyn hnh mu ta phi truyn thng tin v mng vi mi im ca hnh u t l vi ba mu c bn: mu (R red ), mu lc (G green),

l

(B blue) v mu l mu khng cn truyn tn hiu chi. V vy, dng sng tn hiu truyn

hnh en trng gm xung xa, xung ng b truyn hnh v thng tin v chi c thay th b

truyn hnh thng tin v tn hiu mu.

S tng qut my thu truyn hnh mu.

Hnh 2: s khi ca my thu hnh mu.- Khi chn knh: c nhim v chn lc ly knh cn thu v bin tn hiu thu c thnh tn

hiu trung tn bng cch lyNSf

- THf = TTf

- Mch AFT (mch t ng tinh chnh): nhm n nh tn s dao ng ngoi sai NSf n

tn hiu thu ca knh tn hiu chi


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- Mch tch sng phch: c nhim v bin trung tn ting 1 v trung tn ting 2:

OIRT CCIR FCCTT

ting 1

31.5 32.5 41.25

TT

ting 2

6.5 5.5 4.5

- Mch khuch i trung tn ting SIF: c nhim v khuch i tn hiu in p trung tn ti

th 2 ln ln

- Mch DetFM v khuch i m tn: c nhim v gii iu tn tn hiu ting ri khuch

c cng sut ln a ra loa

- Mch khuch i trung tn hnh VIF: c nhim v khuch i tn hiu trung tn hnh ln

a vo mch tch sng hnh.

- Mch tch sng hnh: c nhim v gii iu bin tn hiu VIF tr thnh tn hiu hnh tng

- Mch khuch i video tng hp c nhim v khuch i in p tn hiu hnh tng hp l

ln a n: chi, sc, ng b, AGC.

- Mch Delay 0,7 ms v khuch i Y c nhim v lm tr tn hiu chi cho hnh nh en

trng(chi) v hnh nh mu(sc) trng khp vi nhau v khuch i in p tn hiu chi ln

a vo mch ma trn chi sc.

- Mch AGC(mch t ng iu chnh h s khuch i): c nhim v nhn tn hiu t sau t

sng hnh kim tra xem ln ca tn hiu c ln khng, c n nh khng, iu khin

khi chn knh v mch khuch i trung tn n nh tn hiu thu.

- Khi mu: l mt trong nhng khi quan trng vo bc nht ca tivi mu, n nh hng rn cht lng hnh nh ca truyn hnh mu. N c nhim v sau:

Tch ly tn hiu C t tn hiu hnh tng hp khuch i tn hiu sc C n gi tr cn thit.

hp vi xung ng b mu, sng mang mu gii iu ch v ly ra tn hiu mu R y v B

a vo mch ma trn chi sc. Mch ma trn v khuch i tn hiu R G B, mch ma trn

nhim v ly tn hiu y, R y, B y trn t l nht nh(cng hoc tr) c ba tn hiu mu


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bn R, G, B sau 3 tn hiu ny c cc tnh (-) c khuch i vi bin v cng sut ln

a n iu ch 3 katot n hnh

- n hnh mu CRT c nhim v bin tn hiu in thnh tn hiu hnh nh.

- Khi ng b mu: c nhim v tch ly tn hiu ng b mu thc hin ng b, ng

cng bc mch to sng mang ph trong my thu hnh h NTSC v PAL, thc hin ng pha

CMT trong my thu hnh h SecamIII B v h PAL. T ng tt knh mu lc thu chng trnen trng hoc chng trnh truyn hnh khc h mu.

- Khi tch v phn chia xung ng b c nhim v tch ly xung ng b dng v mnh ra

khi tn hiu hnh tng hp v phn chia tn hiu iu khin fH v fV vo cc tng qut dng v

mnh.

- Khi qut dng, so pha, OSC, khuch i m, khuch i cng sut dng FBT c nhim v

to ra cc tn hiu qut dng ng b vi my pht v khuch i vi bin ln cung cp

cun li dng, to a in p cao p HV cp cho anot n hnh v mt s in p khc cp cho

li n hnh v mt s mch khc trong my thu hnh.

- Mch to dng in ng quy: c nhim v to dng in c tn s dng v dng in c

s mnh vi bin , hnh dng nht nh cp cho c cu hi t c t trn c n hnh. C c

t ny c tc dng hi t 3 mu R,G,B trn mi phn t ca nh.

- Mch sa mo gi: c nhim v sa xung qut dng v mch a ti cun li dng v

mnh sao cho hnh nh qut c tr li nh ban u m khng b mo hnh hc.

- Mch xa tia qut ngc: c nhim v xa tia qut ngc khi tia in t thc hin qu trn

qut ngc khng mang thng tin.

- Mch chnh lu ngun: c nhim v bin i in p AC thnh cc mc in p AC, DC m

my cn s dng cho cc khi.

- Mch n p: n p in p gip cho cc khi trong TV.

- CPU: iu khin s hot ng ca cc khi trong TV.

Ch : vi mch ngun TV mu phi c n nh cao, gn phi nh, khi c s t bintrong my thu th khi ngun phi c ct ri ra khi cc khi, phi c mch bo v qu p, qudng v qu ti.

II. Khi qut dng


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2.1. Nhim v ca khi qut dng

Nhim v chnh ca khi qut dng l to ra cc mc in p cao phn cc cho n hnhng, ngoi ra khi qut dng cn cung cp xung dng cho cun li ngang li tia in t qutchiu ngang mn hnh.

2.2. 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 AFC t p hi tip v to ra in p iu khin, nu tn s AFC bng H.syn th p iu khin khng => tn s qut dng khng i, nu tn s AFC > tn s H.Syn th mch so pha to ra in p ikhin gim => lm tn s dao ng dng gim v ngc li. ( AFC l vit tt ca Auto FrequenControl : T ng iu chnh tn s dng, H.syn l vit tt ca Horyontal Synsep : Xung ng bdng )

Mch to dao ng dng : To ra xung dng c tn s bng 15625Hz , tn s ny c gc nh nh in p iu khin t mch so pha, trng hp hng mch so pha hoc mt xung H.hay xung AFC th tn s dng bi sai => sinh hin tng mt ng b => nh b xin hoc tringang.

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

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

n hnh, nh p HV = 10.000V, p G2 = 110V, v cung cp xung dng iu khin cun li ngan

2.3. H hng thng gp ca khi qut dng.

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


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My c vo in nhng khng ln mn sng

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 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 .

III. Khi qut mnh

3.1. 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 tin t dn theo chiu dc.


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Xung ng b : iu khin cho mch dao ng , dao ng ng tn s.

S khi - khi qut mnh.

3.2. 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 :


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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 thn

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 .

IV. B knh v b trung tn4.1. B knh.

4.1.1 Nhim v ca b knh.

B knh c 3 nhim v sau:

- Thu tn hiu t mt i pht bng nguyn l cng hng, nhiu i pht cng i n my t

nhng tn hiu t i pht no c tn s trng vi tn s mch cng hng s c thu vo .

- Sau khuch i tn hiu c chn bng cc mch khuch i cao tn, do di tn caton b sng truyn hnh tng i rng ln ngi ta chia lm 3 di sng

+ Di VHL t knh 1 n knh 3

+ Di VHF t knh 4 n knh 12

+ V di UHF t knh 21 n knh 63

+ Cc knh 13 n 20 khng dng trong lnh vc truyn hnh

- To dao ng ni cung cp cho mch i tn

- i tn tn hiu thng qua mch trn tn, tn hiu t i pht c trn vi tn s dao n

to thnh tn hiu trung tn, tn hiu trung tn c tn s c nh t 31,5MHz n 38MHz .

4.1.2 Nguyn l hot ng ca b knh.

thu mt tn s no v loi b cc tn s khc, ngi ta s dng nguyn l cng hng

bng cc mch cng hng .


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Hnh 1: Mch cng hng ni tip Mch cng hng song song

- Dng t in v cun dy u ni tip ta c mt mch cng hng ni tip, c im cmch cng hng ni tip l c tr khng rt nh ti tn s cng hng v c tr khng ln vi c

tn s khc.

- Nu ta u song song t in vi cun dy ta s c mt mch cng hng song song, m

cng hng song song li c c im ngc li l chng c tr khng rt cao ti tn s cng h

v c tr khng nh i vi cc tn s khc .

Mch cng hng cao tn RF trong b knh.

Hnh 2: Mch cng hng cao tn RF.

Trong b knh Ti vi mu ngi ta s dng Diode Varicap ( Diode bin dung ) lm t in tr

cc mch cng hng,c im ca Diode bin dung l : chng c in dung thay ikhi ta p v

n mt in p ngc thay i, Diode ny s thayth cho cc t xoay trong cc mch d sng b

in p .

- Mch cng hng cao tn RF c th gm nhiu mch cng hng ni tip kt hp vi cc

mch cng hng song song, trong cc mch cng hng c s tham gia ca diode bin dung


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c th thay i tn s cng hng thng qua s thay i in p .

- Dng in p VT ( Vol Tuning = in p d knh ) i vo cc mch cng hng ny

cc diode bin dung mt in p ngc, in p VT c th thay i t 0 n 28V.

- Gi s khi chnh VT = 10V th c hai mch cng hng tn s l f2, khi mch s cho

s f2 i qua , nu ta thay i gi tr VT sao cho mch cng hng ti f1 th mch s cho tn s f1

qua .

4.1.3 Cc s khi trong b knh.

a) S khi b knh

Hnh 3: S khi ca b knh.

+ Mch cng hng c nhin v chn ly mt knh sng.+ Mch VHL khuch i cc tn hiu ca cc knh 1 n knh 3.

+ Mch VHF khuch i cc tn hiu t knh 4 n knh 12.

+ Mch UHF khuch i cc tn hiu t knh 21 n knh 63.

+ Mch OSC to tn s dao ng ni.

+ Mch Mixer c nhim v i tn.

+ VT (Vol Tuning) l in p d knh, in p VT thay i t 0 n 28V.

+ AGC ( Auto Gain Control ) l in p t ng iu chnh khuch i ca knh, in p

khong 6V

+ in p BU l 12V cp cho di UHF hot ng

+ in p BH l 12V cp cho di VHF hot ng

+ in p BL l 12V cp cho di VHL hot ng

+ Trong mt thi im ch c mt trong ba in p BU, BH hoc BL c cp in.

+ B =12V l in p cp ngun chung cho b knh


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+ AFT ( Auto Fine Tuning ) T ng tinh chnh tn s d sng, in p ny c th khng s

dng.

+ IF l chn tn hiu trung tn ra.

b) S mch iu khin ca b knh.

Hnh : S mch iu khin ca b knh.

- IC chuyn mch iu khin cung cp in p cho cc chn BU, BH, BL, trong mt thi ich c mt trong 3 chn trn c cp in.

- Mch iu khin p d knh VT bao gm :

+ in p chun 33V c cung cp t ngun 110V gim p qua in tr khong 10K v

gim c nh trn mt diode zener 33V.

+ Lnh VT t vi x l

+ n Q1 c nhim v thay i in p VT t 0 n 28V a vo chn VT ca b knh.

- Khi ta d knh, tng ng vi vch d sng tng dn l in p VT cp cho knh thay i

n 28V.

c) S mch dng d knh v nh knh.


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Hnh : Mch dng d knh v nh knh.- Trong qu trnh d knh, khi thu c tn hiu nt nht th qu trnh d knh t ng dng

hoc t ng nh, nh vy phi c mt mch pht hin im tn hiu nt nht => chnh l

mch AFT trn IC trung tn.

- Mch AFT tch mt phn tn hiu Video u ra trung tn to in p AFT, khi khng

tn hiu, chn AFT c in p thp, khi c tn hiu in p AFT tng ln, trong qu trnh d knh

thu c tn hiu in p AFT tng dn, n im nt nht th in p AFT khng tng v bt

gim => chnh l im c tn hiu tt nht.

- in p AFT c a v chn AFC ca vi x l thc hin qu trnh dng d knh v n

knh t ng.

- qu trnh d tay ( Menu Search ) khi thu c tn hiu in p AFT tng bo v vi x l

dng qu trnh d knh ti im nt nht, nu ta nh th in p VT ti im s c nh vo

Memory.

- Nu ta t ch d knh t ng ( Auto Search ) th mi khi in p AFT tng n nh =

IC vi x l t ng nh li im in p VT vo IC nh Memory.

- Sau khi d knh xong, nu ta bm vo s knh nh th gi tr in p VT li c xut

IC nh.

4.1.4 Cc s c thng gp v knh.

* My khng thu c tn hiu, mn nh c nhiu khng c hnh

Cc nguyn nhn dn n hin tng trn l:


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+ Mt tn hiu an ten nh t dy an ten, t nm cm anten.

+ Mt in p d knh VT.

+ Mt in p BU, BH hoc BL

+ in p AGC b sai.

+ Do hng knh

* My thu c tn hiu nhng cc knh u b nhiu

Cc nguyn nhn dn n hin tng trn l :+ Do t an ten , nm an ten.

+ in p AGC b sai.

+ in p B+, BU, BH hoc BL b gim < 9V.

+ Do hng knh

* My thu c di UHF nhng khng thu c trn di VHF hoc ngc li.

Cc nguyn nhn dn n hin tng trn l:+ Mt in p cung cp cho di VHF ( nu mt di VHF ) hoc mt in p cung cp cho d

UHF (nu mt di UHF).

+ in p VT b gim.

+ Do hng knh.

* My ang xem th di knh mt hnh.

Cc nguyn nhn dn n hin tng trn l:

+ in p VT b thay i , thng do cc t gy trn ng in p VT b d hoch t ho b

kh.

+ in p 33V b st p do diode Zener b d hoc t giy song song b chp.

+ Do hng cc Dit Varicap trong b knh.

4.2 B khuch i trung tn.

* Nhim v ca b khuch i trung tn.- Khuch i tn hiu trung tn t b knh a sang, mch khuch i tn hiu trung tn l n

sinh nhiu trn mn hnh.

- Tch sng th tn ly ra tn hiu Video tng hp

- To in p t iu khuch cho b knh AGC v mch K trung tn.

- To in p AFT a v CPU t ng dng ch d knh


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V. Chuyn mch AV

5.1 S tng qut v nguyn l chung ca chuyn mch AV.

S khi.

Hnh : S tng qut ca chuyn mch AV.

Nguyn l ca chuyn mch AV.

- Tn hiu Video ca ng Tivi sau tch sng c a qua mch chn ting sau i nchuyn mch AV.

- Tn hiu thu t u VCD c khuch i m sau a n mt u vo th hai ca IC

chuyn mch AV.

- Lnh AV t vi x l i vo IC chuyn mch iu khin chn ly mt trong hai tn s tr

- Tn hiu ra ca IC chuyn mch l tn hiu tng hp ca 3 tn hiu :

+ Tn hiu chi Y

+ Tn hiu sng mang mu C

+ Xung ng b dng H.Syn v xung ng b mnh V.Syn

- Tn hiu trn c khuch i m cho kho ln ri c chia lm 3 ng cung cp tn h

cho cc mch : x l chi, gii m mu v tch xung ng b.

5.2 S nguyn l mch chuyn mch AV


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Hnh : S chuyn mch AV.- Tn hiu Video ng Tivi ra khi IC trung tn chn s 1 i qua mch chn ting L1, X1

c khuch i m qua n Q1 i tip qua t ni tng C2 n chn 1 IC chuyn mch

- Tn hiu ng Video i vo qua rc cm c khuch i qua n Q3 ri c ghp qua

so quang l IC4 tip tc i qua t ni tng C3 vo chn 2 IC chuyn mch

- Mch mu vng trn s l mch AV cch ly nhm cch ly rc cm u VCD vi mass m

mch AV cch ly c ngun nui ring c ly t mt bin p nh c s cp u vi chn AFC

cao p

- Vi cc my c b ngun cch ly th khng c mch AV cch ly nh trn m tn hiu Vide

thng vo chn t C3 i vo IC chuyn mch

- Lnh AV/TV i t chn 2 IC Vi x l vo chn 4 ca IC chuyn mch

- Tn hiu ra chn 3 i qua t C4 sau c khuch i m qua n Q2 ri c chia lm

ng

- Tn hiu Y i n mch x l chi, Tn hiu C i n mch gii m mu, Tn hiu H.Syn vV.Syn i n mch tch xung ng b.

VI. Khi x l tn hiu chi.

6.1 Nhim v ca khi x l tn hiu chi


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S tng qut mch x l tn hiu mu v chi

Nhim v ca khi x l tn hiu chi l :

Khuch i tn hiu chi ( tn hiu nh en trng ) iu chnh sng mn hnh

iu chnh tng phn

Xo tia qut ngc dng v mnh

T ng gii hn sng mn hnh .

6.2 Cc mch trong khi x l tn hiu chi


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Cc mch trong khi x l tn hiu chiKhi x l tn hiu chi thng tch hp trong IC tng cng vi khi gii m mu, khi c c

mch nh sau : Mch Clamp l mch gim in p mt chiu ca tn hiu chi Mch Contras iu chnh bin ca tn hiu chi, khi bin tn hiu chi

thay i th tng phn thay i .Mch Shapness l mch b tn s cao cho tn hiu chi nhm lm tng i gai

sc ca nhMch Bright l mch iu chnh in p mt chiu ca tn hiu chi, khi chnh

Bright in p DC ca tn hiu chi thay i =>in p DC trn 3 Katt n hnh thay i => thay i .

Cc lnh Contras, Shapness, Bright c iu khin t IC vi x l.Mch ABL( Auto Bright Limited ) t chn ABL ca cao pc chnh lu ly


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chiu m a v hai ng Bright v Contras c tc dng t ng gii hn sng .Xung dng HP a v mch chi nng in p thm tn hiu chi nu mt xung ny t

hiu chi s b mt . Tr chi DL1 c tc dng lm chm tn hiu chi 0,7 s ch tn hiu mqu trnh x l chm hn, trong cc my th h mi tr chi c tch hp trong IC

VII. Khi gii m mu7.1 Nhim v ca khi gii mKhi gii m c nhim v : Gii m tn hiu sng mang mu Choma (C) ly ra ba tn

mu R-Y, G-Y, B-YTn hiu C c iu ch theo ba h l : NTSC, PAL v SECAM v vy khi gii m Ti

phi c kh nng gii m a hNu h hng khi gii m th vn c hnh nh en trng do tn hiu chi vn cnS tng qut ca khi gii m nh sau :

S tng qut ca khi gii m mu 7.2 Nguyn l lm vic ca mch gii m h NTSC


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S nguyn l mch gii m NTSC Trong qu trnh iu ch ba tn hiu R-Y, G-Y v B-Y ngi ta m ho tn hiu G-Y v

hai tn hiu cn li sau hai tn hiu R-Y v B-Y c iu ch vo sng mang C tn s

3,58MHz ( H NTSC) hay 4,43MHz ( H Pal) , hai tn hiu R-Y v B-Y cng c iu ch vo

tn s nhng c pha lch nhau chng nhiu sang nhau my thu tn hiu C c tch ra nh mch lc gii thng BPF (Ben Pass Finter ) i v

khi gii m Tn hiu i qua mch ACC( Auto Color Control ) c t ng iu chnh v mu sc,

Color t CPU i vo mch ny thay i m nht mu . Sau hai tn hiu C ca R-Y v B-Y c tch ra thng qua cc mch lch pha tn hi

+90 v -90

Mch R-Y Detect tch sng ly ra tn hiu R-Y Mch B-Y Detect tch sng ly ra tn hiu B-Y Mch Ma trn tng hp ti to tn hiu G-Y Mch OSC to dao ng 3,58MHz cung cp cho mch tch sng mu Mch Phase lm lch pha tn hiu dao ng => c tc dng iu chnh sc thi mu, ln

tint t CPU i n iu chnh sc thi mu


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Busgate l cng nhn dng tip nhn xung dng i vo, xung dng H.P ( Horyontal Pu

vo lm nhim v ng b tn hiu mu Ident l mch nhn dng, nhn dng s c mt ca dao ng v xung dng bo cho

mch trit mu Kitler l mch trit mu s trit tiu mu sc trong cc trng hp mt tn hiu dao n

hay mt xung dng .7.3 Nguyn l lm vic ca mch gii m h PAL

S nguyn l mch gii m h PALH PAL iu ch tn hiu R-Y chm so vi tn hiu B-Y cch nhau mt khong thi gian

dng qutTrong qu trnh gii m khi tch hai tn hiu , tn hiu B-Y c i qua tr m bo hai

hiu ra cng v vy mch gii m h PAL c thm linh kin tr mu, my i c tr mu ngoIC, trong cc my mi y tr mu c tch hp trong IC

Mch to dao ng cho h PAL l 4,43MHzH PAL khng c mch iu chnh v Phase v khng c lnh TintCc mch khc c s dng dng chung vi h NTSC


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H PAL v h NTSC khng tch ri m ch tch ra cc thnh phn khc nhau, lnhSystem ng vai tr chuyn mch gia hai h.

VIII. Khi khuch i cng sut sc (k video).

8.1 Nguyn l tng hp tn hiu hnh nh.

Tn hiu Video Analog m Card Video cho ra gm 3 ng:

- Tn hiu Video - R (mang thng tin v mu ca nh).

- Tn hiu Video - G (mang thng tin v mu xanh l ca nh).

- Tn hiu Video - B (mang thng tin v mu xanh l ca nh).

8.2 Ngun gc ca tn hiu R,G,B.

- Theo nguyn l phn tch v tng hp mu sc trong t nhin th mi mu sc bt k tth phn tch thnh ba mu c bn l (R), xanh l (G), xanh l (B) v ngc li t ba mu

bn trn ta cng c th tng hp thnh mt mu bt k, chnh v vy mt bc nh c hng trimu nhng thc cht my tnh ch lu li ba mu c bn ca mi im nh m thi.

-Ngun gc ca tn hiu R, G, B l do bc nh mu c phn tch thnh ba bc nh ngt khi chng mi c thu vo, sau cc bc nh ny c i thnh tn hiu Video nhnguyn l qut hoc nh cc Sensor (cm bin).


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- a vo my tnh lu tr hay x l, cc tn hiu R, G, B phi c i thnh tn hidng 0, 1;

- Khi cho hin th bc nh ra mn hnh, cc tn hiu s ca bc nh li c i thnh thiu Analog thng qua Card Video v cho ra ba tn hiu R, G, B sau cc tn hiu ny c

khuch i qua tng khuch i Video ri a ra n hnh tng hp li hnh nh.

8.3 Nguyn l tng hp nh mu trn n hnh.

- Khi c ba tn hiu mu a n ba Katt , mn hnh s cho ra bc nh mu trung th


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-Nu mt mt tn hiu mu th mu sc ca hnh nh tng hp s b sai khc vi mu sca nh gc.8.4 Nhim v, s v v tr khi khuch i video.

Nhim v: Khi Video c nhim v khuch i ba tn hiu mu R (), G (xanh l ) v(xanh l ) ln bin ln trc khi a vo iu khin cc Katot n hnh pht x.

-Ngoi ra khi Video cn trn tn hiu hin th, iu chnh tng phn, cn bng trncho mn hnh.

S khi:- Khi khuch i video c hai tng chnh v hai mch ph.- Tng tin khuch i Video - Pred Video Amply.- Tng khuch i cng sut - Video OUT.- Mch to hin th - Display.

- Mch cn bng trng - Bias.


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- Tng tin khuch i Video c nhim v khuch i ba tn hiu t Card Video a sanln bin ln cung cp cho tng khuch i cng sut, ngoi ra tng ny cn thc hin chnh tng phn, cn bng ba tn hiu R, G , B.

- Tng khuch i cng sut Video gm ba tng khuch i song song, khuch i cho b

mu R, G, B, tng ny c th s dng cc cp Transistor hoc s dng IC cng sut.- Mch BIAS l mch phn cc p mt chiu cho ba Katt, mch c nhim v cn bngtrng cho mn hnh, cc my i c mch ny thng c ba bin tr cn chnh l R-Bias, GBias v B-Bias. Trong cc my i mi, cc bin tr ny c thay th bng cc lnh t vi x

- Mch Display gii m tn hiu hin th, tn hiu hin th t vi x l a ti thng qua hng Data v Clock c IC Display gii m ly ra cc tn hiu R,G,B sau chn vo tn hVideo, IC Display c th c tch hp trong IC tin khuch i Video.

V tr khi khuch i Video:Nm trn v n hnh, pha sau ui n hnh.- Trn v ui n gm c cc IC:

+ IC tin khuch i Video l IC nhiu chn. IC tin khuch i s dng ngun Vcc 12tn hiu t CPU ti c a thng vo IC ny, ba tn hiu ra c a sang IC khuch i csut.

+ IC khuch i cng sut l IC gn trn to nhit. IC cng sut c Vcc l 90V, tn hiui t IC tin khuch i ti, tn hiu ra cung cp cho ba Katt n hnh.

+ IC gii m hin th Display : l IC nh , Vcc cho IC Display l 5V, tn hiu vo l DaClock ly t IC Vi x l, tn hiu ra l R, G, B c a sang IC tin khuch i trn vi hiu Video.

IX. Khi ng ting.- Bao gm cc khi khuch i cng hng lc ly trung tn ting, loi b cc thnh

tn s khc , khi tch sng iu tn ly ra m tn sau qua khi khuch i m tn, cnsut m tn pht ra loa.

- S khi ca ng ting:


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- Tn hiu iu tn FM i cng tn hiu Video tng hp c tch qua t giy => i quamch cng hng u vo i vo tng khuch i trung tn ting => sau khi K ln bin

ln tn hiu a sang mch tch sng iu tn ly ra tn hiu m tn => sau tn hiu mc khuch i qua mch cng xut ri a ra loa pht li m thanh.

Qu trnh x l tn hiu ting my thu.

- Tn hiu FM c tch ra khi tn hiu Video tng hp v i n mcx l ting a h .

- Mch x l tinga h : Mch ny c kh nng tip nhn cc h ti4,5MHz - 5,5MHz - 6,0MHz v 6,5MHz khi thu t cc i pht c h ting khc nhau .

- Mch tch sngiu tn : Tch tn hiu m tn ra khi sng mang iu tn FM .- IC chuyn mch : Tip nhn thm tn hiu ting t u VCD .- Mch iu chnh m lng : iu chnh m lng to nh.- Mch khuch i cng sut : Khuch i tn hiu m tn ln bin ln ri a ra

pht ra m thanh .Mch x l ting a h v tch sng iu tn.


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- Tn hiFM c khuch i sau c chia lm 2 nhnh nhnh trn gm 3 thch anh u song son5,5MHz -6,0MHz - 6,5MHz i vo IC Mixer , nhnh di i qua thch anh 4,5MHz .

- Lnh System s ng m cho nhnh trn hay nhnh di hot ng, Th d lnh System c in p => n Q3 dn =>u tt nhnh di xung mass, v n Q2 dn => Q1 tt=> m cho nhnh trn hot ng, v ngc li khi lnh System khng c in => nhn

trn s b kho v nhnh di hot ng .- Mch Mixer l mch trn tn. Gi x tn s vo l f1, tn s dao ng l f2,s ra l f3 ta c : f3 = f1 ; f3 = f1 + f2 ; f3 = f1 - f2

- Nu tn hiu vo l 5,5MHz - 6,0MHz - 6,5MHz s i qua c cc thch antng ng i vo IC phch => u ra IC u c tn hiu 6,0MHz v i qua thach anh 6,0M sang mch tch sng iu tn.

- Nu tn hiu vo l 4,5MHz s c nh hng i qua nhnh di sang mtch sng iu tn .

- Mch tch sng iu tn c cc thch anh cng hng tn s 4,5MHz hay

6,0MHz l cc thch anh cng hng u ra .


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X. n hnh mu

10.1 Cu to n hnh mu

* Cu to ca mn hnh :Mn hnh mu c cu to bi cc im Phosphor c kh nng pht sng ra cc mu

xanh l , xanh l khi c tia in t bn vo, cc im mu ny c xp sen k to thnh

im tam RGB gi l im nh (Pixels), mt im mu th ch pht ra mt mu c cng

thay i, nhng mt im nh th cho v s mu thng qua nguyn l trn mu, tuy cc im

mu ch ng cnh nhau nhng do im mu qu nh v khong cch gia chng qu ngn,

thng khng phn bit c hai im ring bit v c cm gic l mt mu tng hp.

S im nh ca mn hnh mu l khong 500.000 im, v s im mu s l 500.000

= 1.500.000 im , v vy mt im mu c kch thc rt nh, nhn thy r ba im mu,

dng knh np soi vo mn hnh, khi ta s nhn thy cc im mu ch ng gn nhau m


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* 3 Katt : KR , KG , KB

L ni pht x ra 3 dng tia in t i song song bay v pha mn hnh, dng pht x t

ch bn vo cc im R, t KG ch bn vo cc im G, t KB ch bn vo cc im B, ch

tnh (khng c hnh - mn sng c nhiu trng ) in p 3 Katt c phn cc khong 100 150V DC, cc Kato pht x c chng phi c nung nng nh si t. pht x ca

Katt s gim dn theo thi gian s dng, khi hnh nh s m dn v thiu chi tit v t

thng gi l n hnh gi, nu cc Katt c pht x khng cn bng, th hnh nh s b sa

mu v ta gi l n hnh b lch tia, trong cc trng hp trn ngi ta thng tng in p

t ln 1 n 2V cho pht x tng theo => qu trnh gi l kch n hnh.

* Si t Heater :

C nhim v nung nng gip cho 3 Katot pht x ra tia in t, si t c cung cp 4

nu n c nh hoc 6,3V nu l n c trung , 3 Katt c 3 si t u song song, trong tr

hp n hnh b mt hn mt tia th thng do b t si t => t si t th ta ch c th th

n hnh

* Li G1 :

Cn gi l li khin c nhim v iu khin dng pht x, tuy nhin trong Tivi mu th

li khng s dng v em u xung mass.

* Li G2 : Li gia tc

Gi l li gia tc v n c nhim v tng tc tia in t bay v mn hnh, li c cun

cp in p khong 400V ly t trit p Screen trn thn cun cao p, khi chnh nm Screen

p G2 thay i => sng mn hnh thay i, G2 thng c iu chnh khong 60% gi

nm Screen, nu G2 qu cao => mn nh s qu sng v m km theo tia qut ngc, nu

G2 qu thp => nh b ti hoc c th mt nh sng.* Li G3 : Li hi t

Gi l li hi t v n gip cho ba tia in t pht x t 3 Katt hi t li ng trn m

hnh => gip cho hnh nh c sc nt cao nht, in p G3 ch c mt gi tr ng cho m

hnh, gi tr G3 khong 5000V v cn tu theo kch thc n hnh, in p ny ly t trit


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Pocus trn thn cun cao p do c th iu chnh c, nu ta chnh sai p Pocus => hnh

s b nho, cc chi tit khng r, v in p Pocus l kh cao do v ma m t , in p

Pocus thng b d r lm hng nha sau ui n => Sinh hin tng nh b nho , bt m

sau mt thi gian mi r dn* Cc chi tit bn ngoi :

- Cun li tia: Cun li tia c gn vo c n hnh c nhim v li tia in t qut t t

sang phi, t trn xung di. c hai cun li tia l cun li dng v cun li mnh, cun li

c cung cp xung dng t chn C n cng xut dng, cun li mnh c cung cp xung

mnh t IC cng xut mnh, nu mt xung i ti cun li dng th mn hnh ch c ct sng d

nu mt xung mnh i ti cun li mnh th mn hnh ch cn mt vch sng ngang.

- Nam chm Puryty: Nam chm Puryty l cc vng trn gn quanh c n hnh ngay sau

cun li tia, Nam chm Puryty c nhim v hng cho ba tia in t pht x t 3 Katt bn

vo im mu tng ng ( th khng chnh ) nu ta chnh sai => nh s c vin mu, khi

phi theo vt sn nh du ca nh sn xut chnh tr li v tr c.

- Cun dy kh t - Degauss: l cc vng dy qun xung quanh n hnh, cun kh t c

nhim v kh t d trn n hnh do t trng tri t nhim vo khc phc hin tng nh

t, nhim t l hin tng mn hnh b loang mu, sai mu thnh tng vng, cun kh t ch

ng trong khong 2 n 3 giy u khi mi bt my, dng in qua cun kh t rt mnh

khong 1,5 n 2Ampe, cun kh t c iu khin t mt in tr kh t nm trn b ngu

trc cu Diode chnh lu.

- B mt n hnh: B mt n hnh c cu to bi cc im Phosspho c kh nng ph

cc mu (Red), Xanh l cy (Green) v Xanh da tri (Blue), dng tia in t pht x t c

Katot s p vo cc im mu tng ng, pha sau mn hnh ( bn trong) cch mn hnh kho1cm l mn chn c l, c 3 im mu cho ta mt im nh v mi im nh c mt l nh

mn chn, mc ch ca mn chn ngn cc tia in t khng bn vo cc im mu sai v


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10.2 Nguyn l hot ng.

Nhim v ca mn hnh l ti to li hnh nh

10.2.1 iu kin mn hnh pht sng

- Cao p hot ng bnh thng

+ C in p HV

+ C in p G2

+ C in p G3

- C in p si t

- Chnh lch gia Katt v G1 khng qu 100V

- n hinh tt.

=> V vy khi Monitor khng c mn sng l do mt trong cc nguyn nhn trn.

10.2.2 Nguyn l hot ng

n hnh mu s dng phn mn hunh quang dng hin th cc im nh, cc i

nh pht sng theo ng mu sc cn hin th cn cc tia in t tc ng vo chng to ra

pht x nh sng. ng phng CRT s to ra cc tia in t p vo mn hunh quang hin

cc im nh theo mong mun.

Cm u phng in t bao gm ng phng cc chm tia in t . y c ba ng pv cho ba mu khc nhau. Trong mi ng c mt si t (kiu ging dy tc bng n si

chng ta thng thy, nhng tc si t y th c hnh dng c bit hn nhiu). Khi lm

th si t c nung nng n nhit nht nh cc in t t do trong kim loi ca si

tc nhy khi b mt. Khi cc in t nhy ra th chng c nm trong mt in trng c


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hiu in th rt ln gia ng phng in t v Anot th b ht vo in trng thnh cc

chm tia in t.

to ra mt tia in t c th hi t ti mt n ca mn hnh , ng CRT c cm thu k

t (h thu knh t ny khng ging nh cc thu kinh quang hc). li cc tia in t n

im mong mun th ng CRT c cc cun li tia theo hai phng (ngang v ng) iu khi

ny n cc v tr trn mn hunh quang.

Cc chm tia in t c iu khin theo cc to khc nhau bi cc cun li tia t

hi t ti cc im l ca mt n, xuyn qua cc l ny th chng p vo lp pht pho m

s hin th i vi cc mu sc khc nhau. Mi l trn mt n l mt im nh, tng ng vmu -xanh lc-xanh lam.

Tong Hop Truyen Hinh

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