Acer AL502 User manual

15-inchLCDMonitor
AL502
Service G uid ervice

Page 1CircuitD escription
AL502
1. Audio circuit (Circuit diagrams Main PWB)
1.1Audioinput
The audiosignalinputreceivedfromthe audioinputterminal(JK011)isappliedtothe amplifierI001of4(L-
CH)and9(R-CH)through the low-pass filterconsisting ofR040,R041,R042,R043,C040 andC041.
Inthisamplifier,controlsofVolumeandmuteareconducted.The audiosignalcontrolledatthe pin6determines
the attenuationofoutputofthe amplifiers.Since then,the signalisoutputtothe jackP003.
1.2Audiooutput
The audiosignalisoutputfromP002outputterminalofthe Audioblocktothe internalspeakersystem.
2. Power supply (Circuit daigrams MAIN PWB)
2.1Line filterconsistsofC801,T801,C802,C803,C804.Iteliminateshigh frequency interference tomeetEMI’s
requirement.
2.2Rec &Filter:
Bridge diodeD801convertsAC source intopulsedDC.ThispulsedDCissmoothedandfilteredbyC805.
R802isan NTC(negative thermalcoefficient)resistor,usedtoreduce inrushcurrenttobewithinsaferange.
2.3Powertransformer:
T802convertsenergy forsquarewave frompowersource C805tosecondarysidetogenerate+12Vand+5V.
2.4Output:
The squarewave fromT802 isrectifiedbyD809,D810,then filteredbyC817,C822 togenerate+12Vand
+5Vrespectively.
2.4.1A5VpowersupplyforLCD module,CPUandlogicisgeneratedfromthe powersource.
2.4.2I308 :3-terminalregulator
A3.3VpowersupplyforI306analogisgeneratedfromthe 5Vsource.
2.4.3I308 :3-terminalregulator
A3.3VpowersupplyforI306digitalisgeneratedfromthe 5Vsource.
Q302,Q303 ON/OFF controlforLCD Module
ON/OFF controlisperformedforpowerON/OFF andalsoforthe powersaving sequence.
2.5Driver:
Q803drive T802fromPWMcontrolofI801 forpowerconverted.
2.6FB:
Negative feedbackCKTconsistsofphotocouplerI802andadjustableregulatorI803.Itcan maintainoutput
voltages+5Vand+12Vatastablelevel.
2.7PWM:
2.7.1Start:When poweristurnedon,Q801 conductsdue tobiasfromC805andR805,R803.C807ischargeda16
voltandastarting currentabout0.3mA topin7ofI801.I801startstooscillateandoutputsapulsetrain
through pin6todrive Q803.
2.7.2OPP :When Q803turnson,C805 suppliesalinearlyincreasing trianglecurrentthrough the primaryinduc
tance ofT802 tothe driverQ803,once the peakvalue ofthiscurrentmultipliedbyR811exceeds1volt, pulse
trainwill beshutdownimmediatelytoprotectQ803,T802frombeing burnedout.
2.7.3Regulation :Ifoutputvoltage +5Vgoesup,the RterminalofI803getsmorebias,accordinglyphototransis
torandphotodiodeflowsmorecurrent. The voltage ofpin2goesuptoo,making the pulsewidthofpin6to
becomenarrower.Sothe outputvoltage +5Vwill bepulleddowntoastablevalue.

Page 2 CircuitD escription
AL502
2.7.4OVP :If+5Vgoesuptoo much,the inducedvoltage onpin4ofT802becomeslarge also.Supposethatitis
over18 volts,ZD801 conducts,pin3ofI801ispulledupover1volt. The pulsetrainatpin6goesdownto
zero,shutting Q803 off immediately.
2.7.5SCP:Ifoutputterminalisshorttoground,phototransistordoesnotconduct,hence Q806doesnotconduct
either.Then oscillationofI801isstop,shutting Q803off immediately.
3. On-screen circuit (Circuit diagrams Main PWB)
I300Embededfunction.
On-screen menu screen isestablishedandthe resultantdataareoutputfromI300(CircuitdiagramMAINPWB).
4. Video input circuit (Circuit diagram MAIN PWB)
The AC-coupledvideosignalisusedtoclampthe blacklevelat0V).
5. Definitionconverter LSI peripheral circuit (Circuit diagram MAIN PWB)
I301MRTV2gmZAN1isthe definitionA/DconverterLSI.
The analogR,G,Bsignalinputenteredfromthe videoinputcircuitisconvertedintothe digitaldataofvideo
signalthrough the incorporatedA/Dconverter.Basedonthisconversion,thisdevice performsinterpolation
during pixelextension.The source voltage forthisdevice is3.3Vandthe systemclockfrequency is12MHz.
The withstandvoltage levelforthe inputsignalvoltage is3.3Vand5V.
6. System reset, LED controlcircuit (Circuit diagram MAIN PWB)
6.1Systemreset
Systemresetisperformedbydetecting the rising andfalling ofthe 5Vsource voltage atI302.
6.2LEDcontrolcircuit
Green /amberislitwiththe controlsignalofthe LEDGREENandLEDAMBERsignalpin43,42 fromI303
(CircuitdiagramMAINPWB).
7. E2PROM forPnP (Circuit diagram MAIN PWB)
H15AAU / H15AAR Power Board Block Diagram
LineFilter Rec.
&
Filter
Power
Transformer
Output Rec. & Filter
PWM Driver
FB

Page 3CircuitD escription
AL502
8. E2PROM (Circuit diagram MAIN PWB)
Datatransferbetween I304andCPU(CircuitdiagramMAINPWBpage 4/7(I303)iseffectedthrough the IIC
busSCL(pin9)andSDA (pin8)ofI300orSCL(pin42)andSDA pin39 ofI301.The datatobetransferredto
each device arestoredinI304.
nI300controldata.
nOSDrelatedsettingdata.
nOthercontroldataforservice menu.
9. CPU circuit (Circuit diagram MAIN PWB)
I303 (MTV312M64)(SM89516C25)or(W78E62BP-40)functionsasthe CPU.
The source voltage forthe device is5.0Vandthe systemclockfrequency is12MHz.
9.1DetectionofPOWERswitch status
The CPUidentifiesthe ONstatusofthe twopowersupplies.The identificationismadewhen the powersupply
isturnedoff.Forexample,ifthe powersupplyisturnedoff withthe POWERswitch,the POWERswitch mustbe
turnedonwhen activating the powersupplyagain.Ifthe powersupplyisturnedoff bypulling outthe power
cord,then thispowersupplycan beturnedonbyconnecting the powercord,withoutpressing the POWER
switch.
9.2Display modeidentification
9.2.1Functions
(1)Display modeidentification
nThedisplay modeofinputsignalisidentifiedbasedonTable1,andaccordingtothefrequency andpolarity
(HPOL,VPOL)ofhorizontalorverticalsyncsignal,presenceofthe horizontalorverticalsyncsignal,andthe
discriminationsignal(HSYNC_DETECT,VSYNC_DETECT).
nWhen themodehasbeen identifiedthroughthemeasurementofhorizontalandverticalfrequencies,thetotal
numberoflinesisdeterminedwithaformulaof“Horizontalfrequency /Verticalfrequency =Totalnumber
oflines.“Finalidentificationcan bemadebyexamining the coincidence ofthe obtainedfigurewiththe
numberoflinesforthe modeidentifiedfromthe frequency.
nWhen thedetectedfrequency ifthesync signalhaschanged,thetotalnumberoflinesshouldbecountedeven
through itisrge identifiedfrequency inthe samemode.Then,itisnecessarytoexamine whetherthe preset
value forthe verticaldisplay positionofItem4-3hasexceededthe totalnumberoflines.Ifexceeded,a
maximumvalue shouldbesetup,which doesnotexceedthe verticaldisplay positionofItem4-3.
(2)Out-of-range
Thisout-of-rangemodeisassumedwhen the frequency ofthe horizontal/verticalsignalisasspecifiedbelow.
nVerticalfrequency :Below50Hzorabove85Hz
nHorizontalfrequency :Below24KHzorabove75KHz
(3)Powersave mode
The powersavemodeisassumedwhen the horizontal/verticalsignalsareasspecifiedbelow.
nIfthereisnohorizontalsyncsignalinput.
nIfthereisnoverticalsyncsignalinput.
nIfthehorizontalsyncsignalisoutsidethemeasuringrangeofI300.
nIftheverticalsyncsignalisoutsidethemeasuringrangeofI300.

Page 4 CircuitD escription
AL502
Table1
Attention:
1.When resolutionbeyond1024x768isinputted,resolutionisloweredwithDownscaling to1024x768,and
indicated,andOSDshouldindicateOUTofRange.
9.3UserControl
9.3.1RelatedportsofI303
Port
Pin No.
I/O
Signal name
Function Remarks
P1.5 7IPOWER Power switch input Power ON , OFF
control
P1.1 3IDOWN switch input ( ) key
P1.0 2IUP switch input ( ) key
P1.3 5I-- switch input ( - ) key
P1.2 4I++ switch input ( + ) key
Polarity
Mode
No Resolution
H-
freq
(
KHz)
Band Width
(MHz) H V
1. 247 VGA 720 x 350 70Hz
31.47
28.322 +-
2. 102 VGA 720 x 400 70Hz
31.47
28.322 -+
3. 103 VGA 640 x 480 60Hz
31.47
25.175 - -
4. 182 MAC 640 x 480 66Hz 35 32.24 - -
5. 173 VESA 640 X 480 72Hz
37.86
31.5 - -
6. 109 VESA 640 X 480 75Hz 37.5 31.5 - -
7. 104 VESA 800 x 600 56Hz
35.16
36 + +
8. 116 VESA 800 x 600 60Hz
37.88
40 + +
9. 110 VESA 800 x 600 75Hz
46.88
49.5 + +
10. 117 VESA 800 x 600 72Hz
48.08
50 + +
11. 108 MAC 832 x 624 75Hz
49.72
57.283 - -
12. 118 VESA 1024 x 768 60Hz
48.36
65 - -
13. 217 SUN 1024 x 768 65Hz
52.45
70.49 - -
14. 157 VESA 1024 x 768 70Hz
56.48
75 - -
15. 141 VESA 1024 x 768 75Hz
60.02
78.75 + +

Page 5CircuitD escription
AL502
9.3.2Functions
Controliseffectedforthepush-switchestobeusedwhen the userchangestheparameters,inordertomodifythe
respective setting values.Whetherthe switch hasbeen pressedisidentifiedwiththe switch inputlevelthatis
turned“L”.
Each switch inputportispulledupatoutsideofASIC.
Each parameterisstoredinthe EEPROM,the contentsofwhich areupdatedasrequired.
9.4ControlofdefinitionconverterLSII300.
9.4.1Portsrelatedtocontrol
Pin No.
I/O
Signal name
Function
159 IIRQ interrupt signal
5I/O SCL serial clock
6I/O SDA serial data
9.4.2Functions
MajorfunctionofI300 areasfollows:
(1)Expansionofthe display screen.
(2)Timing controlforvarioussignaltypes.
(3)Power-supplysequence (LCD panel).
9.5I2Cbuscontrol
9.5.1RelatedportsofI303
Port
Pin No.
I/O
Signal name
Function
P1.7 14 OSCL IIC bus clock
P1.6 13 I/O SDA IIC bus data
9.5.2I2C-controlledfunctions
The following functionalcontrolsareeffectedbyI2C.
(1)ControlofEEPROMI304 forparametersetting.

Page 6 CircuitD escription
AL502
9.6PowerON sequence
When the POWERswitch ispressed,the POWEROFFsignalisturned“H”.When this“H”potentialisdetected,
the CPUbeginstoestablishthe respective powersuppliesaccording tothe sequence shownbelow.
POWER
PPWR
D-SHCLK
INV_EN
LED
DATA

Page 7CircuitD escription
AL502
9.7PowerOFF sequence
When the POWERswitch ispressedwhilethe powersupplyisON,the POWERONsignalisturned“H”.When
tshownbelow.his“H”potentialisdetected,the CPUbeginstoturnoff the respective powersuppliesaccording
tothesequence
POWER
PPWR
D-SHCLK
INV_EN
LED
DATA

Page 8 CircuitD escription
AL502
10. Inverter
Thisunitoperatesonan outputvoltage of15Vfrompowersource.
10.1Regulator:Q101 geta+5VDC forI102 powersupply.
10.2UVP:Q106turnsoff when the Vinisunder14V.Then pin3ofI102ispulledlowandinverteroff immediately.
Thatisthe undervoltage protection.
10.3ControlIC:I102 (OZ960S)
10.3.1Enable:When pin3ofI102 isover1.5V,I102 works.Ifitisunder1.5V,I102 turnsoff.
10.3.2OSC:When I102 enabled,R108/C115 (pin17/pin18ofI102)determine the operating frequency.
10.3.3SST:C104(pin4ofI102)providessoft startfunction.
10.3.4Ignition:R109(pin8ofI102)provideshigheroperating frequency formorestriking voltage until regulation
offeedbackoflampcurrent. C103 (pin1ofI102)determine the striking time.
10.3.5Dimming control: The dividedvoltage ofR106/R105/R104controlthe dutypulseofburst-modetodrive Q105
andperformawidedimming controlforthe CCFL.The burst-modefrequency isdeterminedbyC116.
10.3.6Regulation:Pin9/pin10ofI102provideregulationofthe CCFL currentfromfeedback.The non-inverting
reference (pin10ofI102)isat1.25Vnominal.
10.3.7Protection:Open-lampprotectioninthe ignitionperiod isprovidedthrough bothpin1andpin2ofI102.
Removalofthe CCFL during normaloperationwill triggerQ104 toturnsonandshutsoff the inverter.This
islatch function.
10.3.8Outputdrivers:The configurationpreventsany shoot-through issue associatedwithbridge-typepower
conversionapplications.Adjusting the overlapconductionbetween I101 P-MOSFET andI103N-MOSFET,
I101N-MOSFET andI103P-MOSFET,the CCFL currentregulationisachieved.
10.4Full-bridge switching/Transformer:I101/I103/C123/C125/T101/T102 composefull-bridge switching to
convertDCintoACfordriverthe CCFL.
10.5Detection:C124/C119/CR102detectthe outputvoltage andensurearatedvoltage bypin2ofI102.Q102/Q103
ensurenotaopen-lamp.
10.6Feedback:CR101/R120/R121/D108sensethe lampcurrentfornegative feedbackandregulation.The divided
voltage onR121 will beat1.25V.
InverterBoardBlockDiagram
VCC
Regulator
U.V.P. Enable
OSC
SST
Dimming
control
Outputdriver
Protection
Ignition
Regulation
ControlIC:OZ960
ON/OFF
Full-bridgeswitching Transformer Lamp
Feedback
Detection
Brightness
control
VDD

Trouble Sh ooting Page 1
AL502
1. No display of screen (Screen is black, color of LED is amber)
DoesOSDdisplay when
youpushkey button.
Yes
Checkifthe sync signal from Computer
isoutputand if the video cableis
connectednormally.
No Proceed"NoOSD display"section.
OK
Proceed"Checkingthe resolution change
ICmovement"section.
NG Inputthesync signal of computer, or
changethecable.
Whenasignal isn't
beinginputted,it is
indicatedwith"VIDEO
INPUT".Itis indicated
with"OUTOF RANGE"
atthetime of the
frequencythatit can't be
distinguished.

Page 2 Trouble Sh ooting
AL502
2. Nothingdisplays on screen (Screen is black, color of LED is green)
Isbacklightlit?
OK
DoescomputeroutputRGBvideosignals?
NG Refer"Checkingthebacklightunit"section
OK
CheckOSDmenuisdisplayedonscreen
whenyoupushthe"PROCEED"key.
NG
1)Changepatternofvideosignaloutputonthe
host.
2)Reconnectthevideocable.
3)Changethevideocable.
Checkthevideocableforfailure.Checkthehostfor
outputsignalwithallblackonly.
OK NG
Proceed"Abnormalscreen"section.
NextPage

Trouble Sh ooting Page 3
AL502
Continue
Check if the voltage on I308 pin3 that
is high level DC at 5V.
Check the 3.3 V power are supplied on I308 pin 2.
OK
NG
OK NG
Failure point
I308 Failure
Is a dot clock being outputted under the
condition that a LCD module is connected to
P303 pin 44?
OK NG
Failure point
1) I300 failure
2) Printed wire broke between I302 and P303 pin 44.
Check the H-sync pulse of negative polarity is
output on P303 pin 38 at TTL level.
OK NG Failure point
1) I300 failure
2) Printed wire broke between I300 and P303 pin 38.
Check the V-sync of negative polarity are
output on P303 pin 40.
OK NG
Next Page
Failure point
1) I300 failure
2) Printed wire broke between I300 and P303 pin 40.
Failure point
1) Printed wire broke between P301 and I308

Page 4 Trouble Sh ooting
AL502
Continue
Check the data enable of positive polarity
are output on P303 pin 42.
OK NG
Failure point
1) I300 failure.
2) Printed wire broke between I300 and P303 pin 42.
Check the data signal output on P306 and
P303 R, G, B data pin.
OK NG
Failure point
1) I306 failure.
2) Printed wire broke between I300 and P303 , P304
data line
Failure point
1) The cable broke between P303 , P304
and LCD module.
2) LCD module failure.

Trouble Sh ooting Page 5
ALC502
3. Checkingtheback light unit
Is+15VsuppliedtoP803
pin3,4toinverterPWB?
OK NG Failurepoint
Invertercabledisconnection.
ChecktheINV_ENsignaloftherectangleinputI307pin5atTTLhighlevel
OK
NG Isa"H"levelbeingoutputintheTTLlevelfromI300pin143
Or,isINV_ENsignaloftherectanglebeingoutput?
NG
Failurepoint
Printedwirebrokebetween
I300pin143andI307pin5
CheckthePWMsignaloftheinputfromI303pin7isaBRIsignal
OK NG Failurepoint
1)Printedwirebrokebetween
I303pin17andI307pin3
2)I307failure.
Failurepoint
1)Invertercabledisconnection.
2)InverterofLCDmodulefailure.

Page 6 Trouble Sh ooting
ALC502
OK NG
Failurepoint
1)NoR,GandBvideosignaloutputfromhostcomputer.Check
computer
2)Videosignalcabledisconnection.
OK NG
ChecktheR,G,Bvideosignal fromcomputerinputon
D-SubR,G,Bconnector.
ChecktheR,G,BinputsignalsonI301pin12,20,28,
respectivelythattheirlevelis0.7Vp-pmaximum.
IsthepulseoftheTTLlevelbeingoutputtoP303,P304
fromthedatalineofI300?
Failurepoint
IncaseoftheRedsignal.(AGreenandBluesignalisthesame
path,too.)
1)PrintedwirebrokebetweenD-Sub(R)andI301pin12.
2)R341short.
3)C321open.
4)R362open.
OK NG Failurepoint
1)PrintedwirebrokebetweenI300datalineandP303,P304
2)I317failure.
CheckthenegativehorizontalsyncpulseoutputtoP304
pin38fromI300pin80atTTLlevel.
OK NG
Failurepoint
1)PrintedwirebrokebetweenI300pin80andP304pin38.
2)R351open
CheckthenegativeverticalsyncpulseoutputtoP304pin
40fromI300pin75atTTLlevel.
OK NG
CheckthepositiveDEpulseoutputtoP304pin42from
I300pin74atTTLlevel.
OK NG
ChecktheSHFCLKOUTPUTtoP304pin44fromI300
pin44atTTLlevel.
OK NG
Process"CheckingtheresolutionchangeICmovement"
section.
Failurepoint
1)PrintedwirebrokebetweenI306pin44andP307pin44.
2)FB314open
3)FB315open
4)C380short
5)C381short
Failurepoint
1)PrintedwirebrokebetweenI300pin75andP304pin40.
2)R352open
3)C416short
Failurepoint
1)PrintedwirebrokebetweenI300pin74andP304pin42.
2)R355open
3)C382short
4. Abnormal screen

Trouble Sh ooting Page 7
ALC502
5. NO OSD display
OK
NG
Check the input of pulse from I300 pin 5, 6.
Proceed "Checking the resolution change IC movement" section.
Failure point
1) Printed wire broke between I306 pin 5 and I303 pin 9.
2) Printed wire broke between I306 pin 6 and I303 pin 8.

Page 8 Trouble Sh ooting
ALC502
6. Abnormal plugandplay operation
6.1AbnormalDDC2
Confirm the input of serial data on I305 pin 6 synchronize SCLK at TTL level.
OK
NG Failure point
I305 failure.
Failure point
1) The host machine isn't communicating in DDC2 mode.
2) The video cable may have failed or may not to have connections for DDC.
3) Between I305 pin 6 and P302 pin 15 may have failed.
4) R337 open.
5) Cable failure.

Trouble Sh ooting Page 9
ALC502
7. Checkingtheinterfacecircuit of sync signal
7.1Checking the controlcircuitofhorizontalsync pulse
Check the horizontal sync signal on I301
pin 94 TTL level.
OK NG
Failure point
1) Video cable may have failed.
2) Printed wire broke between P302 pin 13
and I301 pin 94
3) R346, R348 open
4) C372, C373 short
Process "Checking the resolution change IC
movement" section.
Check the vertical sync signal on I300 pin
44 TTL level.
OK NG Failure point
1) Video cable may have failed.
2) Printed wire broke between P302 pin 7 and I300 pin 44
3) FB308, R343 open
4) C369 short
Process "Checking the resolution change IC
movement" section.
7.2Checkingthe controlcircuitofverticalsync pulse

Page 10 Trouble Sh ooting
ALC502
8. Checkingtheresolution change IC movement
Isthere+3.3Vsupply onI300pin17, 21, 57,77,79,97, 102, 117,137,154,156, 157and65.
OK NG
Is12MHzclockinput to I300pin3at
TTLlevel?
Proceed"CheckingtheDC/DCconverter circuit"section.
OK
NG Is12MHzclockoutput from X300
atTTLlevel?
OK NG
Failurepoint
Printwirebroke between X301and
I300pin3.
Failurepoint
X300failure
Is+5.0Vsuppliedto I300 pin2at
Highlevel?
OK NG Checktheoutputof 5.0V "H"pulse
fromI302pin 6.
OK
NG Is5.0Vsuppliedto I302 pin7?
Failurepoint
I300failure
Failurepoint
Printwirebrokebetween I302pin6
andI300pin 2.
OK NG
Failurepoint
I302failure
Failurepoint
1)FB319open
2)Powersource

Trouble Sh ooting Page 11
ALC502
9. No power on
9.1Nopoweron(I)
Checkoutputvoltage+5V,
+15Visrightor not.
NG OK
Checkpowerswitchis turn on
ornot.
OK NG
Checkpowercord( P801), Signalcable
(P302),P802,P803,CN102,CN103
isconnectedright or not.
Itisnotpower board
problem.
Turnswitchon.
OK NG
CheckC805isabout DC
140V-330Vornot.
Connectitright.
OK NG
CheckC807isover
10Vornot.
CheckF801,D801,P801
andrepairthem.
OK NG
Checkpin6of I801 have
samepulseornot.
CheckR805,R803,I801
andrepairthem.
OK NG
Checkpin1of T802 have
samepulseor not.
Checkperipheralcomponents
ofI801and repair them.
OK NG
Checkpeakvoltageof R811 triangle
pulseisupto 1 volt ornot.
CheckQ803,R813,R814, D806
,R812andrepair them.
OK NG
CheckD809,D810,C816, C821, T802
havesameshortcircuit, or the output
+5V,+15Visover load.
CheckD804,R807and
repairthem.
NG OK
Checkfeedbackcircuitaround I802,
I803andtheother components
andrepairthem.
Repairthem.