No Display on Desktop Motherboard.
In these case before you begin your troubleshooting,First test RAM and SMPS.
If the RAM is faulty then motherboard will turn ON,but there will have no display.It can be faulty RAM or issue with the module slot in which the RAM chip is inserted.Clean that Module with IPA liquid and dry/wipe it with dry tissue or you can use ear bud.
Take care no dust get into the module holes or remains on the slot pins.Clean the Module properly,then re-insert the RAM chips and see if RAM is getting detected.
Other then AM other thing to get confirmed is SMPS. If SMPS is faulty or not giving properly voltages,then also mother board will turn ON,but have no display.If SMPS is complete dead,then mother board will not turn at all.
NOW,once you are confirmed that SMPS and RAM is good,then please follow other fault find troubleshooting:-----
THE MOST COMMON REASON AND SOLUTION FOR POWER ON BUT NO DISPLAY:---
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REASON 1) Faulty 32K RTC Crystal for ICH.
Solution 1)
Test RTC crystal frequency. If its less then 32Khz, then it has to be replaced.Please note frequency can be ok, if its +/- 10.So if it shows 22 Khz or 42 Khz then its considered to be ok.
If the frequency is very low replace RTC and if frequency is very high,then replace it.
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REASON 2) Faulty PWM section.
Solution 2)
In these case complete PWM section needs to be checked.In PWM section there is PWM chip,PWM channel filter coils, High side and low side mosfets,mosfet driver chip.
ON some motherboards the mosftet driver chip is integrated into the PWM chip,these can be confirmed once you get the datasheet of PWM chip.Just google the chip number of PWM chip and these will give you idea,if its only PWM chip or its integrated with mosfet driver chip.
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REASON 3) Faulty I/O Chip.
Solution 3)
Get the datasheet for Super I/O chip and test its volt IN and Volt OUT voltages.Also test its Power Good voltages.If the voltages are not satisfactory,then replace Super I/O chip.
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REASON 4) Faulty MCH or its power supply Mosfets.
Solution 4)
Test capacitors for ground on base plate of MCH. The non-polar capacitors should only be ground on one side and not both sides.
If you feel any of the capacitor is ground on both sides,then it can be the issue with MCH.In that case,also test the voltages to the capacitor.The non-polar capacitors should give minimum 1.2 volts reading at one side and no reading at other side.If there is no reading,then it clears problem with MCH. In that case the MCH BGA chip needs to be removed and re-balled by re-balling procedure.
Beside MCH there is a power supply mosfet,these mosfets are to supply power to the functioning of MCH. Also check the voltages at mosfet. The minimum voltage out should be at least 1.2volts.,If less that 1.2 volts is coming out,then its issue with MCH power supply mosfet.It has to be removed from board and tested out board.Most probably replacing the mosfet will help.
There are two types of mosfets. NPN and PNP.
Let it be NPN or PNP minimum 240 ohms to maximum 960 ohms should be there while testing mosfets. If the reading is less then 240 ohms then replacing the mosfet is advisable.
If the Power supply mosfet is tested good and non-polar capacitors near and on base plate of MCH are tested good,then its rarely a chance of faulty MCH.
If the MCH is getting overheated and very hot to touch,then,try re-balling MCH and these should help.
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REASON 5) Faulty ICH or its power supply Regulators.
Solution 5)
Like MCH have mosfet for power supply. ICH have regulators for power supply.
But on some motherboards there is mosfet in case regulators.So don't get confused.
You can say,some motherboard have mosfets and some have regulators.Its also board manufacturer,what he prefers good,he will use that semiconductor.
Now,if in case the ICH is getting overheat and very hot to touch.Then first check the power supply regulator near ICH,if that regulator is giving output voltage of less then 1.2 volts,then its considered to be faulty.
If the regulator voltage is checked ok,then check frequency for ICH RTC. Its 32 Khz RTC crystal.If the frequency generated by RTC is not giving satisfactory results,then it has to be replaced.
If the power supply regulator for ICH and RTC is checked ok and still the ICH is overheating,then it has to be removed and ICH BGA chip has to be re-balled by re-balling process.
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REASON 6) Faulty RAM power supply section
Solution 6)
Test the RAM power supply section.It depends on type of Motherboard.On some motherboard,there is only one driver chip to control ram power supply section.On some board there is just an OPAM to control RAM power supply section.But basically there is mosfet. One high side mosfet and one zener diode.The zener diode to supply constant voltage and it grounds if voltage exceeds then required.But if too heavy voltage comes then zener diode gets short and grounds all voltage to save major short circuit to the motherboard.
And there is one driver chip to control/ drive mosfets and one filter coil to supply required voltage to ram module.
The voltage actually depends.
For DDR Ram module the voltage is 2.5V. For SD ram the voltage is 3.3V. For DDR 2 ram the voltage is
1.8V. For DDR3 RAM the voltage is 1.5V to 1.35V.
So as per per these voltages the voltage depends on Ram Power supply coil.
If RAM power supply section is checked ok and still RAM is not getting detected,then its faulty MCH. Because RAM section is controlled by MCH.
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REASON 7) Problem with BIOS or FAULTY BIOS Chip.
Solution 7) To confirm if Bios is working or not,test the A49 pin of PCI slot.On these pin the frequency has to be checked.Please note that frequency can only be checked by Frequency testing meter.The frequency has to be tested on Hertz mode.That is Hz mode on meter.If the bios is ok,then meter will first show very high frequency and then get stable at 40Mhz.
For example the frequency will first rise to more then 250 Mhz to and above that and then slowly settle down at 40Mhz. If the frequency is no rising to high and just showing very low then its issue related to BIOS.
The other way to confirm its BIOS problem is testing by DEBUG card.
These card has to be inserted in PCI slot.On DEBUG card there is IRDY LED.These LED should blink when system starts up for few seconds,then it remains steady ON.If IRDY LED is not blinking at all while system start up,then its faulty or corrupted BIOS.
In these case re-flashing the BIOS chip helps to resolve the problem.
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REASON 8) A Faulty VGA port
Solution 8) VGA port is the port where you connect VGA cable from monitor to CPU.If there is VGA port in motherboard is faulty then there will be no display problem.
So to confirm the problem with VGA Test the First square pin of VGA port on circuit port.
These 1st pin is square in shape and other pins will be round shape.The 1st pin is power supply pin and its the main power IN pin.These pin Intakes 5 volts and VGA port starts functioning.If these 1st pin is not receiving +5 volts on it then,the issue is there.
You can apply jumper to these 1st pin of VGA port,by other +5 volt point.Like from USB port or from LPT port.
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REASON 9) Faulty Clock Synthesizer chip or its RTC.
Solution 9) Clock synthesizer generates frequency to all the other sections of mother board.If the clock synthesizer is not generating frequency then,other sections will not work.In that case,as per the chip number of clock synthesizer chip.Google the datasheet for clock synthesizer chip and test the voltages for clock synthesizer chip.If the voltages are not satisfactory,then its issue with clock synthesizer chip.
Other possibility can be faulty RTC for clock synthesizer.
Clock synthesizer chip has RTC crystal of 14.318 Mhz.Test the frequency with frequency meter,set on Hz mode.The frequency can + or - 10.For example,if the frequency shown 5Mhz or 6Mhz on out pin of RTC then its OK.Or if the frequency shown is 20Mhz or 24Mhz then its OK.
If the frequency is very less like 1MHZ or 3Mhz or very high like 50Mhz or 60Mhz then its faulty RTC.It has to be replaced.
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Most probably these are the possibilities that can cause power ON but NO Display problem.
Once you check and confirm these faults,you will trace and locate the cause of problem.
If there are any more possibilities for no display,other then these possibilities,please dont hesitate to share your views here.It will help other,who goes through these Article.
Thanks.
For more Help and Understating,its recommended to go through these suggested Links:----------
Troubleshoot Dead Motherboard
http://technoanswers.blogspot.com/2012/10/troubleshoot-dead-motherboard.html
