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TI LIU M HNH DN TRI AMPLY

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M HNH DN TRI AMPLY

1. S KHI CA AMPLIFIER

Mt my tng m bao gm mt dy mch khuch i. Nhng mi tng c mt tn gi

ring ty theo nhim v ca n. Nhng d th no cng nm trong hai phn :

Phn tin K v phn KCS. Phn tin K c ng vo mc cao (AUX) v

phnng vo mc thp vi chc microvolt (t Micro hoc t u t cassette).

M hnh Amplifier c ba bng (Board) mch (K Mic-Aux, Equalizer, KCS)vi cc

cht cp ngun ring. Khi s dng khi no th ta ni dy cp ngun cho khi

1.1 Chc nng v nhim v ca cc khi

a. Mch K Micro: khuch i tn hiu t MICRO a vo. Tn hiu ng voca

tng ny thng rt nh khong vi micro volt.

b. Mch K Aux: khuch i tn hiu t cc ngun ph khc a vo. Ti ng vo ph

nhn rt nhiu ngun tn hiu c bin khc nhau. Nh t Phono c bin vi mv,

t Tape, Tuning, CD, VCR . . . C bin vi trm mv n 1V( tiu chun 600 mv) .

c. Mch Mixer: l mch khuch i c rt nhiu ng vo vi li khc nhau.

Yu cu ca mch ny l phi c n rt thp (nhiu nh). V y l tng khuch i

u tin nn t s S/N ph thuc vo tng ny. Tn hiu sau khi rakhi mch ny phi

c bin nh nhau.

d. Mch m sc: dng chn lc tn s m thanh ty theo s thch nghe ca mi ngi

(Tn hiu m tai ngi cm nhn t 20Hz _ 20KHz). Trong tn s thp t 20 Hz-

500Hz l m trm. Tn s cao t 7.5 KHz _ 20KHz cn ting ni c tn s 1KHz.

e. Mch khuch i thc: khuch i tng cng tn hiu do thng sau khi qua phn

m sc tn hiu b suy hao nn cn khuch i c bin ln a n tng

khuch i cng sut.

f. Balance: dng chnh tn hiu cho 2 loa c cn bng.

g. KCS: y l tng K cui cng trong my tng m, K cho ra CS ln ph hp

vi loa. Transistor CS thng mc kiu y ko v lm vic ch hng AB hay

hng B. Cc amplifier ch khc nhau tng ny v thng dng cc kiu KCS:

- OTL: Out put trasformer less. (Ng ra khng dng bin p)

- OCL: Out put capacitor less. (Ng ra khng dng t)


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- BTL: Brigde transistor line out. (Ng ra dng cu transistor)

h. Mch bo v: bo v tng KCS, Bo v loa.

i. Loa : bin i tn hiu in thnh tn hiu m thanh.

j. Ngun cung cp: ngun xoay chiu 110V hay 220V c chnh lu thnh ngun 1

chiu cung cp in cho ton my. (1 phn khng s dng n p cung cp trc tip cho

KCS, 1 phn qua n p cung cp cho cc mch khc).

Ngun thng s dng 2 dng chnh: Ngun n v ngun i xng.

1.2 Nguyn l hot ng theo s khi

a. Tn hiu t micro hay t cc ngun tn hiu ph khc a ti 2 ng vo Mic v Aux

c bin kh nh c mch khuch i micro v aux khuch i cho bin ln

ln sau a n mch trn tn hiu, sau khi qua mch trn bin tn hiu a n

mch m sc l tng ng nh nhau v ti y tn hiu s c iu chnh c c

m trm hay m bng p ng nhu cu s dng. Sau tn hiu tip tc c a sang

mch khuch i cng sut khuch i cho tn hiu ln ln nghe c trn loa.

b. Ni ngun th chun +12V v mass (GND) t b ngun c to sn cp cho

khi KCS.

c. Ni ngun in p c n p ti khi KCS cung cp cho cc khi khc.

1.2. Mch k cng sut OTL

Mch KCS OTL l dng mch K s dng ngun cung cp l ngun n, c mc

in p cung cp t +30v n +50v. C in p trung im = 1/2Vcc. Xut m ra loa

thng qua t, khng cm dng mch bo v loa

1. Lp rp tng phn(tng) sau cp in v o volt DC. Nu iu kin in p qa

khc so vi thit k th phi xem li cc tr s in tr phn cc.

2. Khi xc nh c iu kin DC th cho tn hiu t my pht sng vo cc B,

dng my hin sng quan st dng sng ng ra.

3. Nu tn hiu ra ln v khng b mo dng l phn mch chy tt.

4. Tng t ta lp cc tng cn li.

5. Ni t lin lc gia 2 tng li v dng my kho st dng tn hiu ti ng ra

6. Ni cc tng li vi nhau v ch khng c gn Transistor cng sut cng sut

v loa vo ngay m ta phi o li in p ti cc im chun trc khi gn Transistor

cng sut cng sut v loa. Lu : Transistor cng sut cng sut phi c gn vo

cc l nhm tn nhit v lt cch in.

7. Mch ngun thng s dng trong mch cng sut OTL:


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S NGUYN L MCH OTL:

Q1: tin khuch i; Q2: Driver; Q3,Q4: Transistor cng sut (cp transistor b ph);

Q3, Q5 v Q4, Q6: ghp Darlington ( tng h s khuch i)

- Volume 50Kohm: iu chnh m lng (bin ) tn hiu ng vo; VR1

100Kohm: dng chnh ly mc p trung im; VR2 500KOhm: chnh in p

phn cc cho Transistor cng sut (dng chnh mc mo ti giao im tn hiu)

- C1, C3: dng lin laic; R8, R10, C7: dng lm mch hi tip dng (Boost-

trap); C2, C6: to hi tip nghch AC, chng mch pht sinh dao ng t

kch (t trung ha); C4, C8: t thot AC, gia tng li tng khch i; C9,

R17: mch lc Zobel, dng chng dao ng t kch (loi b tn hiu vng tn

s cao) v cn bng tr khng vi loa. Trnh c hin tng mo do tr khng

khng cn bng vi loa; C10: tu xut m.


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- li ton mch c th tnh theo h thc sau: K(ton phn) = R6/R5

1.3 Mch Khuych i cng sut OCL

Mch KCS OCL l dng mch K s dng ngun cung cp l ngun i xng, c

mc in p cung cp t 30v n 50v. C in p trung im = 0v. Xut m ra loa trc

tip, phi dng mch bo v loa

1. Lp rp tng phn(tng) sau cp in v o volt DC. Nu iu kin in p qa

khc so vi thit k th phi xem li cc tr s in tr phn cc.

2. Khi xc nh c iu kin DC th cho tn hiu t my pht sng vo cc B,

dng my hin sng quan st dng sng ng ra.

3. Nu tn hiu ra ln v khng b mo dng l phn mch chy tt.

4. Tng t ta lp cc tng cn li.

5. Ni t lin lc gia 2 tng li v dng my kho st dng tn hiu ti ng ra

6. Ni cc tng li vi nhau v ch khng c gn Transistor cng sut cng sut

v loa vo ngay m ta phi o li in p ti cc im chun trc khi gn Transistor

cng sut cng sut v loa. Lu : Transistor cng sut cng sut phi c gn vo

cc l nhm tn nhit v lt cch in.

7. Mch ngun s dng trong mch cng sut OCL c dng:

S NGUYN L MCH OCL


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1.4 Mch khuych i cng sut BTL v bo v loa

1.4.1 Mch BTL

Mch KCS BTL l dng mch K cu i xng, l 2 na mch cu lm vic song

song nhau nhng vi 2 tn hiu ti 2 ng vo nghch pha nhau L dng mch cho ra

cng sut ln vi in p ngun nui thp

- Loa c ko trc tip nn chng c mo bin v mo tn s

- Hiu sut cao, khng kn ti loa

S thc t


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- Q1 v Q2 l cp cng sut mt knh cn cp Q3, Q4 l cp cng sut ca knh

th hai trong mt ampli stereo.

- Q1, Q2, Q3, Q4 u hot ng hng AB, mi transistor ch cho qua mt bn k

phn cc thun. Vi Q3, Q1 (NPN) s dn bn k dng do c phn cc

thun trong lc Q2, Q4 (PNP) th dn bn k m. Hai tn hiu vo cp cng

sut hng AB l hai tn hiu o pha.

- Nu cc B ca Q1 bn k dng phn cc thun th cc B Q4 bn k m

cng phn cc thun, nn cp Q1, Q4 u dn mt bn k. Dng Ic ca Q1,

Q4 u chy qua loa tng gp i. Trong lc Q1, Q4 dn th cp Q2, Q3 u b

phn cc nghch nn khng dn.

- Q2, Q3 c phn cc thun nn cp Q2, Q3 dn. Hai dng Ic ca cp

transistor ny cng chy qua loa cng chiu nhau nn cng c kch mnh gp

i nh bn k trn.

- Cng sut ca loi mch ny rt cao v UMAX =Vcc nn cng sut P rms =

0.78 Vcc^2/2RL. Nh vy khi lp theo kiu BTL th cng sut s tng 4 ln so

vi mch OTL bnh thng.

1.4.2 Mch khuych i OPAMP


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1.4.3 Mch bo v loa

- Mch bo v ny c tc dng lm tr 5 n 10 giy, khi mi m my khng ni loa

vo mch. Nn trnh c ting n loa khi mi m my, v lc in p im gia

khc 0v do cp transistor b ph khng i xng hon ton, gy ra ting n loa lm

kh chu cho ngi nghe v nh hng xu n loa

- Ngoi ra cn c tc dng bo v loa khi c s c chm mch c th dn n lm

chy loa.

Mch bo v loa thc t

- Mi nhm lp rp v cn chnh mch

- o in p phn cc

- o dng qua tng tng khuch i

- o v ghi li kt qa o ti cc im o c trng trn mch

1.5 Mch tin khuych i v lc m sc


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Mch khuch i Micro dng khuch i tn hiu t Micro cho ln a vo

tng khuch i cng sut.(bin tn hiu t Micro a ra rt nh t 1 5 mv).

- Mch khuch i Aux dng khuch i tn hiu t cc ngun tn hiu khc nh

VIDEO, CASSETTE, CD, VCD a vo (Cc ngun tn hiu ph ny c

in p ln hn tn hiu t Micro vi chc ln ).

- V bin tn hiu ca Micro a ra nh hn vi chc ln so vi tn hiu t

ng vo ph. Mun cho 2 tn hiu ny a n loa gn bng nh nhau th h s

khuch i mch Micro phi ln hn nhiu ln mch khuch i Aux.

- Tng khuch i Micro v Aux phi c thit k sao cho t s S/N l ln nht.

Nh vy tng ny thng hot ng ch hng A, phi c bin php chng

nhiu v kh tp m nn.

- Tng khuch i Micro v Aux phi c t xa bin p ngun trnh nh

hng ca in xoay chiu d gy ting .


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1.5.1 Mch tin khuych i

- Q1, Q2: Transistor khuch i tn hiu t Micro a n.

- Q3: Transistor khuch i tn hiu t cc ngun tn hiu ph khc a n.\

- R1,R2: Phi hp tr khng ng vo.

- R3,R6,R10: in tr phn cc cho cc C ca transistor Q1,Q2,Q3.

- R4,R7,R9: in tr phn cc hi tip p cho cc B ca Q1,Q2,Q3.

- R5,R11: n nh nhit cho Q1,Q3.

- R8: in tr hi tip. li ca mch hon ton ph thuc vo ng hi ny.

- VR: iu chnh bin tn hiu ng ra.

- C1, C2, C3, C4, C5: T lin lc.

Nguyn l hot ng ca mch:

+ Khuch i Micro: Tn hiu t micro a n c bin rt nh c vi mV qua R2,

C1 vo cc B ca Q1. Khuch i v ly ra cc C tip tc qua t lin lc C2 vo cc

B ca Q2 khuch i v ly ra C qua t lin lc C3 v c iu chnh bin ng

ra bi VR trc khi a sang tng sau.

+ Khuch i Aux: Tn hiu t cc ngun tn hiu ph khc nh CD, CASSETTE,

RADIO (bin vi chc mV) c a n ng vo Aux qua t lin lc C4 vo

cc B ca Q3 khuch i v c ly ra C qua t lin lc C5 a sang tng sau.


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Nhng h hng thng xy mch khuch i Micro v Aux:

o PAN 1:

- Hin tng: Khi cm Micro ni nghe tn hiu trn loa cn khi s dng ng vo

Aux khng nghe tn hiu trn loa.

- Nhn nh: Mch m sc, cng sut, khuch i Micro vn tt h hng thuc

v khuch i Aux.

- Cch kim tra v sa cha: Kim tra jack cm Aux, ngun cp cho Aux, dy

ni tn hiu, t lin lc, phn cc transistor.

o PAN 2:

- Hin tng: Khi cm Micro ni khng nghe tn hiu trn loa cn khi s dng

ng vo Aux nghe tn hiu trn loa.

- Nhn nh: Mch m sc, cng sut, khuch i Aux vn tt h hng thuc v

khuch i Micro.

- Cch kim tra v sa cha: Kim tra Micro, jack cm Micro, ngun cp cho

mch Micro, dy ni tn hiu, t lin lc, phn cc transistor.

o PAN 3:

- Hin tng: Khi cm Micro vo th nghe ting trn loa, khng nghe c tn

hiu.

- Nhn nh: Do mch khuch i Micro vn hat ng nn khi cm Micro vo

mi nghe ting . Vy h hng thuc phn ng vo ca mch Micro.

Cch kim tra v sa cha: Kim tra micro, jack cm Micro xem c b chm dy tn

hiu v mass

1.5.2 Mch lc m sc (Equalizer)


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Mch m sc dng Equalizer l mch m sc c chia ra lm 5 khong iu chnh

thay i tn s. Thng thng iu chnh cc tn s sau :

100 Hz, 500 Hz,1 KHz, 8 KHz, 14 KHz.

Chc nng linh kin trong mch:

- Q1: Khuch i tn hiu ng vo. (Q1 c mc theo dng hi tip p nng

cao cht lng v trit nhiu hiu qa, rp theo kiu CC li dng)

- Q2: Khuch i tn hiu ng ra. (Q1 c mc theo dng hi tip p)

- VR1 n VR5 kt hp vi cc in tr t in trong cc nhnh t 1 n 5 iu

chnh thay i tn s.

Nguyn l hot ng:

- Tn hiu t tng trc a sang qua t lin lc vo cc B Q1 khuch i v ly

ra cc E. Sau chia lm 5 ng (mi ng iu chnh mt tn s chn

trc). Tn hiu sau khi c chn lc tn s cho ph hp vi nhu cu s

dng c a n cc B Q2 khuch i v ly ra cc C qua in tr hn

bin v ri a tn hiu tip ra tng sau (tng cng sut).

1.5.3 Mch lc m sc (Bass-Treble)

Chc nng linh kin trong mch:

- IC 4558: gm c 2 Op-Amp, c S/N cao, nhiu thp.

- R1: phi hp tr khng u vo.

- VR1: dng iu chnh m trm ; VR2: dng iu chnh m trung; VR3: dng

iu chnh m bng


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2. Cc sa cha tng hp trong amply

Cc dng h hng thng xy ra trong Amplifier v cch khc phc.

- i vi vic sa cha Amplifier th trc ht ta phi nhn nh c h hng

thuc phn no trong Amplifier thng qua nhng hin tng m ta cm nhn

c. nhn nh c nhng h hng xy ra trong Amplifier th ta phi nm

r s khi Ampli cng nh nguyn l hot ng theo s khi.

- Trong nhng bi trc chng ta kho st chi tit tng khi trong Amplifier

v nm c chc nng nhim v cng nh nguyn l hot ng v 1 vi h

hng thng xy ra cc khi. Trong bi ny chng ta c nhim v c kt

nhng hin tng h hng, cch khc phc hc trong nhng bi trc sa

cha 1 Ampli hon chnh ang c s c.

- Nh vy nhn nh c h hng cng nh sa cha nhng h hng.

Qa trnh c tin hnh theo trnh t sau:

- Cp ngun cho my.

Cp tn hiu vo ng vo hay dng tay lm ngun nhiu kch vo ng vo.

- Nhn nh h hng thng qua cc hin tng trong qa trnh th my.

- Sau khi nhn nh h hng thuc khi no th tin hnh sa cha trn khi

v ch khi m thi.

- Sau khi sa xong kim tra li my nu vn cn h hng tip tc sa cha cho

my hon chnh.