Posts tagged motherboard repairing
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In this article we will discuss Power Delivery system in Motherboards . For more in depth training , join PCLR Course of chiptroniks or you can also buy our course materials with online support.
Power delivery—Why & How
Why: Motherboard components need one or multiple stable and clean DC power to work correctly
How: (1) Power Supply directly to motherboard components (2) for the power which Power Supply can not provide directly, DC to DC power converter on the motherboard converts the power and provide to components
Voltages type needed
Postive DC Voltage: generally between 0V to 12V, generated by DC-DC converter 0.75V, 1.5V, 1.1V… or directly from power supply, like 3.3V, 5V, 12V
Negative DC Voltage: typically -12V
Motherboard voltage normally ranges from -12V to 12V
Tips: General speaking
Higher speed component=> lower voltage needed
(especially for IO function)
Current types needed
Simple answer: Power/voltage=current needed
Low power device: <2A, example: Clock chip, LAN…
Medium power device : between 2A to 50A: example: Fan, DIMM, Chipset
High power device: >50A, example: processor, high power DIMM, high end Graphic card etc
The low/medium/high is just general category, no standard
Tips: High current device has higher requirements on the PCB
Space, layers, cost, copper thickness…, all in all, bigger current,
more design challenge for power designer and CAD engineer
Examples: components Voltage & Current
1.0V to 1.5V, 50A to 150A, 130W
1.8V/0.9V for DDR2, 1.5V/0.75V for DDR3, 20A to 40A, 50-100W
Chipset: 1.1V, 10-20A, 5W to 30W
Onboard device: 1.5A, 1-2A, 3.3V, 0.5W to 5W
PCI slot: PCI slot: 12V, 0.5A, 3.3V, 3A, 5V, 1A, 15W, 25W, 75W or more
Fan connector: Depends on fan used, ranges from 0.1A to 5A, 5W to 50W
Normally 1 Components need multiple voltage rails
depends on what function needed, such as ICH need
1.5V, 3.3V, 1.8V…, more function, more voltage rails needed
For example: ICH has more voltage rail than CPU
due to ICH has more functions
Voltage types by components function
Components may need several voltages by functions: below is general category
(CPU), VDD (DIMM), occupy most the power pin of the components
IO Voltage: Core Voltage: Main voltage for core logic, most of the power consumes on the main voltage) for the core function, example VCCP Voltage for BUS, example: CPU Vtt
Reference Voltage: voltage used for signal sampling
Analog voltage: Some components include analog function, so analog voltage needed, such as Video, PLL circuit, analog voltage require to be clean ! Need to be separated from normal voltage
Components may contain 1 or more type of voltages depends on
Function needed, such as ICH need all 3 above voltages
Voltage types by power state
Some voltage are only required for certain power state
Normal Voltage: Voltage existing when the system is at S0 to S2 state, which means system is at ON state, like CPU main power, fan power, which is main power for the system
Battery Voltage: Voltage existing when the system at AC OFF status, it is powered by onboard battery. Example RTC clock
Standby Voltage: voltage always exists at S0 to S5 state (DC OFF), which means system at DC off state, AC power code is plugged, it is used for board power on/off logic and wake up function and some management function and other functions need to be functional at main power off state, remember, when AC power cord inserted, standby voltage exists !!
Aux Voltage: Voltage switch by between Standby voltage and same Normal Voltage, the main reason of Aux voltage is the function is needed through S0 to S5 state, but standby power can not provide enough current at S0-S2 state due to the device consume more power at S0-S2 state then S3-S5 state, so voltage need switch from standby voltage to normal voltage to get enough current , example: DDR voltage 1.8V, when system is at S3, the Aux voltage comes from 1.8V standby power to keep DIMM refresh, after power on to S0 state, Aux voltage switch to 1.8V normal voltage to support DIMM normal read/write (which consume much more current)
Components may contain 1 or more type of voltages depends on
Function needed, such as ICH need all 4 above voltages
Let us take a look at a real sample-Chipset
G41 MCH (north bridge) function/power mapping
(not exactly correct, just for example)
Another example—ICH 10
ICH 10 has require more than 20 voltage rails !! due to lots of functions integrated in ICH 10
Refer to product EDS for pin definition and power requirement
Example 3—PCI-E slot Power requirement
This voltage supply to add in PCI-e card, Card is required to design within this limit
Overall Power Delivery Example–Thurley
Overall Power Delivery Example2—Romley
Motherboard Input Power
Now, we know what kind of power (voltage/Current) needed by components, but where does it come from? Answer: from Power Supply, directly or indirectly
Power Supply Output (motherboard input)
Power Supply output type:
Power supply has multiple DC output rail (NOT connector)
Popular 12V, 5V, 3.3V, -12V, 5VSB and other voltage
12V output may have separate rails, like 12V1, 12V2, etc for 240VA protection
Single output: 12V or other voltage only
Power supply has single DC output, 12V is most popular
Battery is single output example
Power Supply output interface:
Connector: board to board or board to cable connector
PCB gold finger: PCB to mating connector
Most of single output PSU also has standby output, like 5VSB
Power Supply Output example 1
Desktop ATX PSU : Multiple output, cable + connector
Server EPS12V : Multiple output, cable + connector
Power Supply Output example 2
19V Single output, connector, connect to motherboard directly
Hotswap module :
12V single output, gold finger and board to board connector
normally it also has 5VSB output
Motherboard side interface
General Rule: mate with power supply output
Gold finger mating connector
Board to Board connector
Motherboard power rails & Power supply rails
As we talked before, multiple-output power supply has multiple output, each rail will have current limit, and each rail are separated below is example
Same for motherboard, motherboard will also have multiple rails, like 3.3V, 5V, 12V1, 12V3a…, each rail has current requirement, so we need to mapping the power supply rails to motherboard rails to make sure both power supply & motherboard rails can be met
Next page is example
Rail mapping Example
Power supply connector/rail mapping
Power supply rail can be separate to support multiple
motherboard rail, but reverse is NOT allowed!, otherwise it will
Short power supply rails and cause protection
DC to DC converter
So far, we know how power supply provide voltage rail to motherboard, like 12V, 5V 3.3V, etc by connectors or PCB gold finger or other method, but for the other voltage power supply can not provide, like 1.1V, 1.5V, 0.8V, we need DC to DC converter on the motherboard to convert the power supply voltage to the voltage we needed
DC to DC converter also called Voltage regulator (VR)
DC to DC converter (VR) types
(1) Linear voltage regulator
-Clean (little noise)
Simple & Clean (little noise)
-Low voltage drop
(1) Why low current and low voltage drop?
vdrop on the VR= Vout-Vin, so the power loss = I x Vdrop, for example: Vin=3.3V, Vout=1.5V, 2A, so the power loss on converter is (3.3-1.5)x2=3.6W, assume 50C/W, so the temp rise will be 150C, which is burn the components, so only low current and low voltage is allowed, Linear VR only support low current requirement
(2) Why low efficiency?
The efficiency= output power/input power, obvious, it is low efficiency due to the power loss on the converter is big, the bigger difference between Vin and Vout, the lower efficiency is.
(3) Why simple & clean & low cost
It is simple & due to just a few components needed
It is clean due to no switch components, it is easier to place & layout the linear VR
Switching VR Types—Single Phase
Basic working principal is by control the mosfet PWM value to adjust the output voltage, Vout/Vin=PWM%, for example: 12V to 1.5V, PWM=12.5%
Switching VR efficiency is between 80 to 98% depends on VR design, the main power loss is VR Mosfet switching & conduct loss
It can handle high current due to high efficiency
High cost /complex is obvious: it need chip, mosfet, inductor, capacitor…
High noise: due to switching method and mosfet switching, it has much higher noise than linear regulator
We will NOT discuss how VR works here, refer to VR training slides
if you are interested, Overall speaking, VR is a complex technology
Switching VR Types—Multi Phase
Switching VR—single phase 12V to DDR 1.5V
Switching VR—multi phase 12V to CPU Vcore
Linear VR–3.3V to IOH 1.8V
Linear VR–3.3V to IOH 1.8V
VR placement & layout
CPU VCCP VR placement
CPU VCCP VR copper planar
In this article , We will explain the essence of chip level repairing together with the happening future of the chip level technicians . We will also explain How CHIPTRONIKS stands tall in this market .
Every year thousands of Desktop PCs, Servers, Printers, Laptops etc are being sold and these Electronics Products becomes faulty/defective during their warranty as well as after warranty. As it is well known that in the First World Countries, the MNC Companies have monopoly on their products and as such they have tried to dominate the Concept of USE and Throw, secondly the cost of manpower in repairing the faulty devices are so high that the Chip Level Repair Technology can not be justified. As a result these MNC companies who are the manufacturers of Computer Systems and its Peripherals have never favoured the development of the Components Level Repair so that they can sell a complete PCB Assembly of any peripherals at high price.
Motherboard Components are two types
Hole Through Components: Processor Socket (PIII), RAM bank, Expansion slots, I/O Ports, etc
SMD (Surface Mounting Device) Chipset, IC regulator, Mosfets, Tantalum Capacitor, Resistors Processor Socket in the case of PIV etc
Motherboard PCB can be made up of Fiberglass or Bakelite. PCB can be available in multiple layers. The layers structure enables multiple wires to send data without their signal interfering with each other. The multiple layers also add strength to the Motherboard.
Layers of PCB
Single /Double layers
Twelve layers etc
Note that PIII Motherboard available in Four layers & PIV Motherboard available in six layers
Top & Bottom Layers of PCB pass data signal, Clock signal, Reset signals etc
Inner layers of PCB pass Current
Tools used in Motherboard Repairing
Soldering & Disordering Tools
Basic Tools for e.g. Tweezers, Paper Cutter, Scissor etc
Testing tools Debug Card, DMM etc
Hot air Gun/Disoldering Pump
Liquid Flux etc
Motherboard Repairable Condition
- Repairable Condition
- Non Repairable Condition: Service Engineer is not full skill
Due to Non availability of Components or burned or damaged PCB
Represents & Testing of M/B Power section Components
- R – Resistor
- D – Diode
- Q – Mosfet
- C – Capacitor
- L – Inductor
- Q or Tr – Transistor/MOSFET
- F – Fuse
- RN Resistor Network
- CN Capacitor Network
- U IC/Chipset
Resistor: – It is used to oppose the current.
It is checked on Ohmmeter.
It has two legs.
Diode: – It is used to convert the AC to DC.
It is checked on range of Diode.
It has two legs i.e. +ve & -ve. (Dark area shows the negtive)
Mosfet: – It is used to regulate the voltage.
It is checked on range of Diode.
Mosfet show one legs show the value and other show the multimeter value i.e. infinite value
It has three legs i.e. Source, Gate, Drain.
Capacitor: – It is used to store the electricity & purify the impure DC to pure DC.
It is checked on range of mf and also checked on Mega ohm i.e. If capacitor is ok than it show the resistance
It has two legs i.e. +ve & -ve.
Inductor: – It is used to filtration.
It is checked on range of continuity.
It has two legs.
Transistor: – It is used to amplifying the signal.
It is checked on range of Diode.
It has three legs i.e.Emmitor, Base, Collector.
Through Debug Card: It is testing device which can attach on PCI slots and it generates the Hexadecimal Codes from where the system engineer sense the faults in Motherboard.
One thing is noted that the hexadecimal codes are differing according to the BIOS.
Some Common codes are following
Motherboard Testing (Debug Card)
Code OK Memory Error mp Error
00 C0 BC
FF C1 EA
27 D1+continue long Beep
60+continue long Beep
Through BIOS beep Code
BIOS show some beep code in POST screen from where the System Engineer senses the faults in Motherboard. BIOS beep codes are also vary according to the manufacturing of BIOS. Some common BIOS beep codes are following:
BIOS Beep Code
Number of Beeps Solving Problem
1 short Beep System is OK (Acceptance Beep)
2/3/4 short Beep Check the RAM & Video adapter
Card properly connected.
5 short Beep Check the RAM properly installed or not check the mP. Replace the mP & M/B.
6 short Beep Try attaching a difference K/B.
7 short Beep Replace the CPU / M/B
8 short Beep Check the Video Card (Display) 9 short Beep Check the BIOS Chip is properly
Attached or not
10 short Beep CMOS Chip Problems
11 short Beep Cache memory Chip
1Long 3 Short Beep RAM Problem
1Long 8 Short Beep Video Card Problem
Continue long Beep RAM Problem
Precaution while rework on Motherboard
- The value of each component should be same.
- The size of capacitor should be same or less.
- The capacitance of capacitor should be same.
- The resistance of resistor should be same.
- Hot Air Gun should be handled properly
- Working surface should be neat & clean.
Rework on M/B
- Chips, IC
- M/B Power Section i.e. capacitor, mosfets, inductor
- Rework on I/O ports.
- Rebuilding the burned or cuts tracks.
To give Motherboard faults
- System/ Motherboard is giving the display but restart again &again after completing the POST Sol: 1 first of all visualizes the M/B carefully. There can be some burnt or damage tracks or components
2 check the electrolytic capacitor it can be damage
3 checks the crystal oscillator mounting near the clock generation chip replace it
4 The clock generation chip may be bad
5 Bad BIOS
6 Press the north bridge and the south bridge chipset with a grate force with the help of your thump.
7 Reinsert the BIOS.
- M/B is dead no display on monitor and the DEBUG card is giving 00; FF; 88 codes but it is switching on properly.
Sol: 1 First of all checks the physical condition of M/B i.e. burnt or worm out tracks on the M/B.
2 BIOS may be bad or incorrectly flashed
3 check the electrolytic capacitor if found bad replace it, while replacing the electrolytic capacitor you should take care for:
1. The volume or WVC work voltage and capacitance should be same
2. Capacitor size should be same
3. Polarity should be correct otherwise it will blast after some time.
4 bad BIOS replace the BIOS with the same
5 super I/O chip may be bad replace it.
6 check the voltage regulator i.e. MOSFETS replace if found bad
7 If problem is still than check the mp or RAM using
8 If problem is still than problem in m/b
- M/B is dead no display on monitor & the DEBUG card is giving C0; C1; C2; C3; D0; D1; D2; D3etc.
It is switching on properly also the internal speaker is giving the continuous long beep.
Sol: check some burn or worn out track near the RAM slots and Mp sockets
2: check the operating voltage i.e. 3.3 V for SDRAM and 2.5V for DDRSDRAM into the RAM slot.
If this voltage is absent then check the voltage regulator [MOSFETS]
3 clean the RAM slot with acetone .it may be dirty or corrosive camp
4 If all these are ok than replace the RAM
- M/B is dead and is not switching on.
Sol: 1 check the physical condition of M/B
2 Check the CMOS clear jumper it may be set on clear, set it on normal mode.
3 Check the dry soldering on Motherboard Power Connector
4 the super I/O chip may be bade. Replace it.
5 south bridge chips may be bad.
6 some times the M/B inner layers may be damage so in this condition the M/B cannot repair further.
7. Before performing all above actions check the SMPS
- The M/B is switching ON/OFF properly & is giving the display but it hang\halt after completing the POST or after 10-15 minutes.
Sol: 1 check the physical condition of M/B
2 check the M/B’s power connector .it may be dry solder or spark.
3 check the electrolyte capacitor
4 also check the voltage regulator i.e. MOSFETS
5 some time the BIOS may be or incorrectly flashed so refresh or replace it
- M/B is giving the display but the K/B is not working and during POST the following message is display.
“Key board error”
“No key board present”
Solution: 1 the K/B connector may be dry solder
2 Some time there is some burnt track or
component near the K/B connector
3 if still problem proceed than bad super I/O chip
4 Before performing all these actions first of all check keyboard itself
- The M/B is giving the display but parallel port is not working
Sol: 1 check the resistor network mountings near the
- check the track from parallel port to super I/O chip
- Dry soldered or bad parallel port
- Some time the super I/O chip may bad
- The M/B giving the displays but one of the serial port is not working
Sol: 1 serial port may be dry solder
2 check the track from serial port to GD75232 chip and from GD75232 to Super I/O chip
3 GD 75232 chip may be bad
4 Some time super I/O chip may be bad
- M/B is giving the display but FDD connector is not working
Sol: 1Check Dry solders on FDD connector
2 bad floppy drive connector
3 visualize the physical condition of connector and tracks between the FDD Connector and super I/O chip
4 the super I/O chip may be bad
- The M/B is giving the display but not audio out put
Sol: 1 check the audio controller is not disable trey & jumpers on M/B some times. The audio controller is disabling through BIOS so first of all check these setting.
2 If these are ok then check the crystal oscillators and voltage regulator IC LM 78xx; LM 317; LM34 mounted near the audio controller chip
3 Bad BIOS so either replace it or refresh it
4 The audio controller may also be bad.
Voltage used by M/B components
SDRAM: 3.3 V
DDRRAM 2.5 V
DDR2RAM 1.8 V
DDR3RAM 1.5 V
P3 1.45v to 1.95 V
Cel3 1.6V to 2.1V
Cyrix C3 2.0V
PIV & Cel4 1.45V