Kinh nghim ca dn trong ngh sa cha TD

1. Tm hiu my h qua ch my

Khi nhn sa mt my hng, vic trc tin bn hy kho lo hi ch my nhanh

chng xc nh tnh trng ca my thng qua cc cu hi nh: My h lc no? N c

du hiu g khc thng? C cho ai bung my cha? My c b v nc kg? My c b

rt ln no cha? My c hao pin kg? trc sng c mnh kg? Ting nghe c ln

kg?... cng bit nhiu thng tin t ngi dng my, bn s cng nhanh chng xc nh h

hng

2. Quan st trc tip trn my

Trc ht, bn nn tm Pan bng mt (dng knh Lup) xem k cc b phn ca my.

Khi cm trn tay 1 my hng, bn hy quan st v pht hin cc du hiu bt thng ca

my. Cc v tr cn ch l cc ch ghp v my, cc tip im kt ni vi Pin, vi th

SIM c b gh st hay kg? Mn hnh c b vt en hay kg? C vt nc trn v my hay

kg? My c b vo nc hay kg? Xem cc IC c b thay th cha? C mt linh kin g

kg? Bng mch in nhiu lp c b cong kg? Cc phm ng c b , st kg? C vt nt

trn board mch in hay kg?

3. Dng php o in tr

Bn hy o Ohm trn my tt ly mu chun ti cc im kh nghi, ghi li kt qu o

sau i chiu vi kt qu o trn my h. Nu s o nh hn kt qu chun, c l

mch b chm, r, dnh. Nu s o ln hn kt qu chun, c l c ch t, h trn

mch.

4. Dng php o in p o in p cng l 1 phng php pht rt quan trng kho

st tnh bnh thng hay bt thng ca mch in.

Trc ht, bn hy kim tra mc in p ca mch ngun nui. Nu mt p, nguyn do

c th do chm ti, do mt lnh m ngun, t ngun, hay do IC ng m ng ngun.

o p trn chn IC, nu thy mt p, trc ht phi kim tra cc linh kin xung quanh.

Nu thy cc linh kin ny u bnh thng, IC ny c th hng. Khi my ang c tn

hiu, phi dng Volt k AC nhy kim tra bin tn hiu.

Ch : Mc phn cc DC ca cc tn thng t nh hng n nhau. S khc thng

mc DC cho bit vng c linh kin hng.

Mc AC lun c tnh nh hng, n c im xut pht, ln lt qua cc linh kin, cc

im trn mch ri sau cng s n ti. Mt tn hiu thng do cc linh kin AC nh t

lin lc b h mch, cun cm b chm hay b t

5. Dng php o dng in

Dng in l mt i lng rt quan trng, n phn nh trng thi lm vic ca mch

in mt cch chnh xc. Khi cp in cho my vi b ngun DC ngoi (thay cho Pin),

trn hp ngun thng c in k o dng. Bn hy lm quen vi cc ng thi ca dng

in trn my o dng bit cc trng thi khi ng ca my c bnh thng hay kg.

Nu my bnh thng, khi nhn nt m my, ban u dng tng vi chc mA, ri t

nhin tng ln rt ln (khong 200mA), lc ny my ang cho pht sng v cc trm

xin kt ni vi mng. Khi kt ni xong, my s tr v trng thi ch, vo mode

WatchDog, khi dng nui my tr v vi chc mA v thnh thong nhch ln qut

phm.

Mt my n dng qu ln, trn 500mA, du hiu ny cho bit my c linh kin b

chm nh cc t lc b chm hoc r nng. Cc IC cng sut b chm s n dng rt ln.

Bn c th cho cch ly cc mch in xc nh vng c chm. Khi tho 1 ng mch

ra m dng tr v mc thp, nh vy xc nh c vng c chm.

Mt my n dng qu nh hay khng n dng, du hiu ny cho bit trong my c ch b

h mch.

Trong cc s mch in ca nh sn xut, ngi ta thng c ghi dng tiu th chy

trong cc nhnh bn c th kim tra s hot ng ca mch in ny

6. Dng php o i chng

Khi bn c trong tay 1 my tt v 1 my hng ca cng 1 model, lc bn c th dng

php o i chng nhanh chng tm ra ch h.

Bn c th dng phng php o Ohm, o Volt DC, Volt AC, o dng, o dng sng

i chng kt qa ca 2 my.

Nu kg c 2 my ging nhau, bn i chng theo d liu c trn s mch ca my.

y l 1 phng php pht hin hng hc rt hiu qu.

7. Dng php thay th

Mt trong cc cch sa rt hay c dng l cho dn nh, tc thay th ngay cc linh

kin nghi h. 1 IC dng trong my ny c th c dng cho nhiu my khc, do vy, khi

nghi h, bn hy tm n trong cc my khc v ly ra cho thay th. Tuy nhin, trc khi

thay th, bn nn o Ohm i chng.vi IC tt bn ang c. Nu khng thy s khc

nhau, iu ny cho thy cha chc IC bn va tho ra b h.

8. Dng php d nng

Vi cc my c linh kin b chm, n dng ln. Bn c th dng cch d nng

nhanh chng xc nh vng b h hay tm c linh kin h. Bn hy cho cp in vo

mch, ch 1 lc, sau tt ngun v dng tay d ch nng. Nu nng trn IC ngun,

kim tra ti. Nu nng trn IC cng sut, c th IC b chm.

Ch : Nu cp ngun lu s hi cho cc IC khc. V vy, nn gim p ngun dng

vo my khong 200mA. mc dng ny, bn c th yn tm cp ngun thi gian

lu pht hin ch nng m khng lm h thm cc ch khc.

9. Dng php v nhn

Vi cc my h hng c du hiu chp chn, do c nhng ch tip xc xu. Khi ,

v nhn l 1 cch pht hin linh kin c tip im hng v ch cn gia c cc chn hn

cho tt.

Ch : Phi chn ng th nhn khng lm gy board, lm cho my h hi nng hn

10. Dng php ngn mch

Khi bn hiu r cu trc my v cn sa cha hin tng mt tn hiu. Bn c th dng

cch bt cu cho ngn mch tn hiu i qua ng ni tt n cc phn khc. Dng

cch ny s nhanh chng tm ra vng h. Bn cng c th dng dy a ngun in

n cp cho vng b mt ngun.

11. Dng php h mch

Vi cc my c du hiu b chm, n dng ln, dng phng php h mch xc nh

vng c linh kin b chm.

Nu nghi c chm mch phn cng sut PA, hy tho in tr t trn ng ngun

DC cho h mch. Nu dng nui tr li bnh thng l xc nh c vng c linh

kin b chm.

Nu nghi c chm mch in trn np mn hnh, hy rt dy kt ni gia board mch

chnh v mch in mn hnh ra, nu dng nui tr v bnh thng th tm ra ch

chm.

Nu nghi c chm th SIM, hy cho lm h mch ng ngun cp cho th SIM, nu

dng nui tr v mc bnh thng l xc nh c ch chm.

12. Dng php lm sch

Cc my in thoi di ng thng mang i nhiu ni, sau 1 thi gian di s dng, my

b bi hoc b vo nc khin nhiu ch trong my b ten, r st. Do , khi nhn my

hng, trc ht bn hy v sinh cho my. Nu c th, bn cho ra board vi mng siu

m. Cc ch d b ten, r l tip im t phn di ca my, tip im vi th SIM,

vi ngun Pin, vi ng ni, ng nghe

13. Dng my hin sng

Khi c my hin sng, bn nn lm quen vi cc dng tn hiu trong my. Sa bng cch

d tm cc tn hiu trn board l 1 phng php chnh thng v rt c a dng. Cc

dng tn hiu thng gp nh: Xung d liu trn ng truyn, xung nhp ng b, tn

hiu m thoi cc ng ni/ ng nghe, tn hiu xung nhp chnh 13Mhz, tn hiu xung

ng h 32768Hz, tn hiu dao ng ngoi sai LO, tn hiu RF, tn hiu IF.

14. Dng cch d tn hiu

Bn c th t lp rp 1 mch in khuch i hay mch to dao ng t nhng linh kin

c ly ra trong cc my c lm thit b truy tm tn hiu trn board. V d, dng

mch khuych i, bn c th xc nh c c tn hiu m thoi hay kg, vi mch to

dao ng, bn c th dng n cp vo mch, sau kim tra xem n c i qua c

cc tng trong my hay kg.

15. Dng phn mm sa my

My in thoi di ng vn l 1 my tnh nh, nn ngoi cc linh kin chuyn dng to ra

phn cng, n cn l 1 thit b hot ng da trn phn mm trong cc b nh nh

FlashROM, EEPROM. C nhiu my do vic cp in khng n nh hoc do kh qu

nng i khi khng do g c cng c th lm xut hin li trong phn mm. Lc ,

my s khng m c in, khng kt ni c vi mng, hot ng chp chn. Khi

nghi my hng phn mm, bn nn Flash li my. Ngha l cho ci t li phn mm h

thng t trong b nh flashROM.

Trng hp bn c dy kt ni ng loi, kt ni c phone vi my tnh. Bn hy cho

kim tra phn mm trc, trc khi quyn nh tm h hng phn cng. l bin php

quen thuc gi l Mm trc cng sau

16. Dng php gia c cc mi hn

Rt nhiu my do rt, hay sau 1 thi gian dng qu c ng, nhiu im hn s b h

khin cho my cht. Vi loi hng ny ch cn liu php gia c l tr my v trng thi

hot ng bnh thng.

17. Dng dy Jump

My di ng cn rt nhiu ng ni mch v c nhng ng nm lp trong. Nu cc

ng mch lp trong b t, bn phi dng dy jump thay th cc ng mch b

t. Dy jump phi l dy ng rt nh (c th ly t cun cm ca relay), bn ngoi c

lp cch in. Sau khi jump, bn phi dy xung v dng lp sn cch in c nh

cc dy ni ny.

18. Dng php gi dy anten

Khi sa cha cc in thoi di ng b sng qu mnh hay qua yu, bn c th dng 1

on dy nh dng lm anten. Anten c th c hiu l 1 mch ti cao tn, n c lin

quan n hot ng ca khi cao tn RF. Nu a anten ng vo khi RF, bn c th

lm tng mc sng cho cc my yu. Trng hp my bt sng qu mnh dy anten thm

vo cng c dng lm gim mc sng. Anten n gin l 1 dy ng di khong

1cm, t ng ch s ci thin c kh nng thu pht ca my.

19. Dng php iu chnh

Trong in thoi c rt nhiu khi iu chnh nh:

APC (Automatic Power Control), iu chnh mc cng sut pht khi khuch i PA

(RF Power Amplifier). Bn c th thay i tr s linh kin cc mch ny nh: tng gim

gi tr in tr thay i mc in p VAPC qua chnh li cng sut lm vic ca

khi khuch i PA.

AFC (Automatic Frequency Control), iu chnh lch tn cho tn hiu 13Mhz. Bn c

th thay i tr s linh kin mch ny nh tng gim cc in tr, cc t mch lc

thng thp thay i mc in p VAPC, qua , chnh li mc n nh tn s cho

tn hiu 13Mhz.

tng khuch i LNA cng c mch iu chnh n nh bin . tng khuch i

m trc khi vo tng gii m tch sng tn hiu I/Q cng c mch hiu chnh li.

Bn cng c th thay i tr s linh kin c c iu kin lm vic tt hn cho my.

20. Dng php phn tch sa my

y l phng php ti u nht. nm c phng php ny, trc ht bn hy quan

st khoanh vng, sau tm s mch in xc nh s mch cho tng vng.

T s , bn s phn tch nguyn l hot ng ca mch in, sau o t tm ch

hng.

Lm c iu ny, i hi ngi sa phi vng kin thc mch in t, khi bn s

khng ngi i din vi nhng hng hc ca bt k i my no. Nu khng, bn ch bit

3 cch: 1 - Thi nng gia c chn hn, 2- v sinh board mch, 3- dn nh (hay thay th

cc linh kin nghi ng l h).