hi this is MSI H61M-P21 (B3) motherboard MSI motherboards also have a System Model (SM),
and this motherboard's SM is: MS-7680 ver 3.2 so first I check the motherboard with my naked eyes to see if there is water spillage
or if it has been heated before I saw that this part is heated I guess these MOSFETs are probably checked by another repairman before and it is obvious that,
this Bios IC is heated as well and it is probably programmed by another repairman before I don't have much to do with these problems yet to check what the problem of this motherboard is, I use an LED and a power ON/OFF switch you can get a power switch like this from a scrap computer case I got this from a scrap PC case! there is a jack on every motherboard it is called "front panel jack" you can place this switch on it
and turn ON the motherboard easily I place the power switch on front panel jack for power switch, it does not matter which end (positive or negative)
is connected to which end (positive or negative) on the motherboard its task is to just connect and disconnect the power and here is an LED
I got it from scrap motherboard as well LED ends are important!!! its positive end needs to connect to positive end on the motherboard
and its negative to negative end I plug in the LED as well I use a buzzer as well buzzer helps you a lot in troubleshooting I place it on the next front panel jack every motherboard's front panel jack is different some of them are split and some are not split this motherboard has a buzzer itself instead of placing a second buzzer,
I could just use motherboard's own buzzer I placed a second buzzer anyways
because it is my routine so the first voltage that is present on the motherboard, is the voltage provided for motherboard by this battery usually it is a +3V, which enters PCH and a part of I/O and drives a part of this PCH block I'll check the voltage on the motherboard
and show it to you yes, around 2.9V is present one important thing about most motherboards is that, CMOS settings on the motherboard may have problems (in such situation) the first thing I need to do, is to remove the battery from motherboard there is usually a Clear CMOS jack (to clear CMOS,) I connect the pins of Clear CMOS jack to each other or I can connect positive and negative end of the battery to each other there is a 32K crystal in here, some repairmen connect the pins of the crystal to each other so that the problem of the device which does not turn ON, or the device which do not have display, would be solved by Clearing the CMOS!!! I cleared the CMOS I place the battery now the battery provides voltage of a part of PCH as well as voltage of this crystal! let me show the voltages on the pins of this crystal around 230mA is present on this pin and 377mA is present on the other pin so this shows that voltage is present on the crystal and most probably its clock is working let me show you the Clock yes as you see if I press the Auto button, around 32 KHz crystal frequency is 32.770 KHz it's in fact 32.768 this shows that crystal is working normally so NO power is connected to motherboard yet, voltage is present on crystal pins, and its clock is working before I connect power supply to motherboard,
(and switch it ON) let me give you some info about power supply functions there are wires with different colors
on ATX jack of power supply the purple wire is +5VSB as soon as I switch ON power supply switch, +5VSB would enter motherboard
through the purple wire another one is the green wire which is PSON signal and through this signal,
power supply detects if it needs to switch ON fully or not for example,
if I connect this green wire (+5V) to the GND, power supply will be switched ON when power supply switches ON, Power Good voltage (the gray wire) would increase to +5V let me check and show the voltages first I check voltage of purple wire +5VSB is present the same voltage (+5VSB) is present on the green wire as well which is the PSON yes and NO voltage is present on the gray wire right now yes as soon as I switch ON power supply, Power Good voltage (on the gray wire),
would enter the motherboard from power supply I switch ON power supply yes, +5V is present on the gray wire now +3V, +5V, +12V and -12V
would enter motherboard through power supply so you learned about power supply functions I'll continue troubleshooting of the motherboard now! by switching ON the power supply switch, +5VSB enters motherboard through purple wire and after passing a regulator IC, the regulator generates +3VSB! those voltages enter PCH and I/O, first, I/O gets reset when I/O is reset, it sends RSMRST signal to PCH and it resets PCH motherboard is ready when I switch ON, I/O detects that power is switched ON, and it sends Power Button signal to PCH!!! in response to I/O, PCH transfers SLPS4 and SLPS3 signals to I/O, and when I/O receives SLPS3, it decreases PSON voltage to zero and +5V of the green wire drops to zero and motherboard turns ON!!! so this is how the motherboard turns ON as this motherboard is damaged, when I switched ON the board,
it turned ON for a second and turned OFF again because settings are saved on CMOS, I should switch the power OFF and reset Bios settings!!! as I told you in the beginning of the video, I reset Bios in this way OR by constant clicking of the power switch button!!! I place the battery I switch ON power supply again as you saw,
motherboard turned ON for a second and then turned OFF again!!! as I told you in previous videos, this shows a short circuit in the motherboard so let's check the power block of the motherboard on the boardview at first, +5VSB enters motherboard through ATX jack and along with +5VSB, Power Supply On (PSON) enters motherboard (I/O) as well I/O can control the power supply and turn it ON or OFF!!! I'll check +5VSB on ATX jack it enters different blocks it enters this MOSFET (Q23) in here which is a double MOSFET it is made up of a P-Channel and an N-Channel MOSFETs it has two inputs and one output the drain pins of these 2 MOSFETs are connected to each other output can be either of these inputs I explained about this type of MOSFET in previous videos here, two MOSFETs are placed in one IC the upper MOSFET is a P-Channel MOSFET which transfers +5VSB to the system and the lower MOSFET is an N-Channel MOSFET which transfers +5V switch (VCC5) to the motherboard to control which one of these +5 volts should enter system, their gates need to be controlled their gate is controlled by an IC (U19) in here when the system is on Sleep Mode, switch voltages get disconnected!!! and this IC (U19) leads gate of this MOSFET (Q23) and that causes +5VSB to enter 5VDIMM (RAM VCC) and that causes +5VSB to enter 5VDIMM (RAM VCC) and when I switch ON the system, this Controller IC (U19) leads gate of lower MOSFET
(which is an N-Channel MOSFET) and this key gets closed (connected), and +5V switch (VCC5) will be present in here +5V switch enters PWM of RAM VCC
after passing choke (inductor) and 1.5V of RAM VCC would be present on this choke (inductor) 1.5V of RAM VCC is generated by this PWM (U14) in here as well as by these 2 N-Channel MOSFETs I explained how to test these MOSFETs in previous videos but I'll show you how to test them again on the motherboard the next sub-voltage is VTT-DDR
which is generated from 1.5V of RAM VCC the next sub-voltage is VTT-DDR
which is generated from 1.5V of RAM VCC which generates half of 1.5V of RAM VCC, by the help of a regulator
which is generated in switched mode pin 1 is its input
pin 4 is output of regulator this voltage is present on pins 120 & 240 of RAM slot although voltage would be in switched mode so RAM VCC is in this block you are familiar with this block now! RAM VCC has another voltage as well which is +3V that is the +3V of switch I'll check that later,
if RAM had a problem! I don't have much to do with this block for now I was checking, to which blocks +5VSB enters this is RAM VCC block which is checked completely in the next block,
+5VSB enters another MOSFET which is a P-Channel MOSFET (Q28) the IC number is written in here I know it's a P-Channel MOSFET by looking at the IC number gate of this MOSFET (Q28) is controlled by I/O and it can connect or disconnect +5VSB if motherboard faces a problem, I/O can disconnect +5VSB
by sending a signal to the gate of this MOSFET (Q28)!!! so let's see where +5VSB enters as you see,
+5VSB enters this regulator (U40) UP7706 regulator +3VSB would be present on output of this regulator I need to test input and output of this regulator as well as test the input and output pins to each other to see if the regulator is shorted or not so, after I tested this block, +5VSB enters another double MOSFET here it is similar to the double MOSFET above it is made up of 2 P-Channel and N-Channel MOSFETs drains of the 2 MOSFETs are connected to each other and +5V of USB is present on its output and in here, to be able to control which one of MOSFETs to be connected, meaning, which of these keys to be closed (connected), you need to control them through their gate pins the gate pin of these MOSFETs are controlled directly by I/O although in here,
+12V switch enters MOSFET Q27 directly in case I/O wanted to protect the circuit, and there was a short circuit, gate pin of MOSFET gets leaded by this transistor (Q70) and its gate and also by I/O its drain connects to its source (which is the GND) and voltage drops
and MOSFET gets disconnected in the next step,
I check switch voltages the first switch voltage to be checked is +3V switch it enters different blocks such as PCH, I/O, PCI slots, PCI Express and RAM slot 1.8V CPU is provided by +3V switch, which is generated by a MOSFET and an Op-Amp let me show the Datasheet of Op-Amp it is a DUAL Op-Amp I use this section pins 1, 2, and 3 are used pin 2 is source pin of MOSFET pin 3 is fixed on 1.8V and pin 1 is gate pin of MOSFET let me explain these on the boardview MOSFET output (source pin) enters pin 2 and gets compared with pin 3 (which is 1.8V) if MOSFET output voltage is lower than 1.8V, output will be high, gate of MOSFET Q60 gets leaded, and voltage enters to source through drain and gets stabilized on this capacitor (EC37) as long as this voltage is lower than 1.8V, the voltage will be present on this capacitor!!! if this voltage is higher than 1.8V, it gets compared with pin 3 in here, as a result output gets low, gate voltage will be low
and MOSFET will be disconnected and voltage of this capacitor will be lowered over time and with constant connection & disconnection,
1.8V would be fixed on EC37 capacitor so I have checked this sub-voltage as well the next main voltage that I'll check is +5V switch +5V switch enters RAM VCC (Q23) which I checked fully and in here,
it enters USB VCC (Q27) I explained all these when checking +5VSB I can check ohm of this (JPWR1) right here and make sure normal ohm appears! next main voltage to be checked is +12V switch which enters PCI Express slots also enters CPU FAN in here and most importantly, 1.05V PCH VCC gets generated from +12V switch 1.05V PCH VCC gets generated from +12V switch which (1.05V) is generated by MOSFET and PWM
(you see the PWM in here) so now I need to check voltage on ATX jack power 2 (JPWR2) (which is CPU VCC voltage) here are different voltages I can check them one by one
on these chokes for example,
I have CPU GFX Core on this choke which is generated by this PWM and its MOSFETs I can check these MOSFETs one by one, and make sure that they are OK I can check their ohm on this choke and make sure that normal ohm appears! the next voltage is CPU Core voltage (VCCP) one of its phases
is generated by this PWM (U4) and these MOSFETs and its other phases are generated
by PWM (U1) and its MOSFETs I can check these low MOSFETs and PWM (U1) itself
by performing ohm check on this choke and check high MOSFET separately I have checked PWMs so many times next voltage to be checked is on choke 10 it is CPU VTT voltage CPU VTT is generated by this PWM (U29) and its MOSFETs I can check this very easily the next sub-voltage to be checked, is generated by this MOSFET (Q39) and this Op-Amp (U33) which is CPU_SA voltage it uses the second phase of this Op-Amp (U33) pins 5 and 6 are compared with each other and pin 7 (Op-Amp output) controls gate of this MOSFET (Q39) and pin 7 (Op-Amp output) controls gate of this MOSFET (Q39) this is the same as 1.8V of CPU and they do not differ much with each other I want to check power block of motherboard I removed CPU first I check ATX jack +3V switch is present there around 20 ohm appears on this way if high ohm appears on one way,
you don't need to perform ohm check on the other way good ohm appears on +5V switch as well good ohm appears on +12V switch as well high ohm also appears on +5VSB if ohm does NOT appear on one way, I need to perform ohm check on the other way
to make sure that there is no disconnection or short circuit by performing ohm check on the other way, and if ohm appears there,
you can make sure that there is no disconnection as you see,
good ohm appears here and there is no disconnection or short circuit here I perform ohm check on -12V usually ohm does not appear on -12V I can perform ohm check on both ways of -12V yes Power Supply ON (PSON) signal is NOT shorted and it is not disconnected as well I check ohm of PWROK signal this is ok as well +12V CPU is left to be checked yes this is ok PWMs and MOSFETs that generate the voltage of
sub-voltages are left to be checked so I start from the top this double MOSFET generates +5V RAM VCC it comes from two directions I explained them before high ohm needs to appear on this way on P-Channel MOSFET and low ohm on the other way yes lower MOSFET is an N-Channel one low ohm appears on this way high ohm on the other way this shows that MOSFET is NOT shorted or disconnected! here I have PWM of 1.5V of RAM VCC drain of this MOSFET is connected on this choke I can perform ohm check on drain to GND and make sure consumer, PWM and low MOSFET are OK and make sure consumer, PWM and low MOSFET are OK so let me perform ohm check in here good ohm appears I perform ohm check on the other way low ohm needs to appear here,
yes so this shows that low MOSFET, 1.5V consumer, and PWM don't have problems only the high MOSFET is left to be checked high MOSFET is an N-Channel one let me check that as well low ohm appears on one way and high ohm appears on the other way so, high MOSFET is ok as well 1.5V of RAM VCC is ok VTT DDR generator regulator is left to be checked its pin 1 is input of 1.5V
I already performed ohm check on it it is ok on this way I perform ohm check on its pin 4 (output) it is OK too I perform ohm check on both ways I need to perform ohm check on input to output, to make sure there is no short circuit inside good ohm appears here as well I checked RAM VCC block here I have a MOSFET which connects & disconnects +5VSB by I/O let me check this MOSFET,
which is a P-Channel one high ohm appears on this way and low ohm needs to appear on drain to source, because it's a P-Channel MOSFET!!! so this MOSFET is OK too here is 1.05V PWM of PCH I can perform ohm check on drain of low MOSFET or on this choke
with GND make sure of the health of consumer, low MOSFET, and PWM!!! 7 to 8 ohm is good on this way different ohm needs to appear on the other way yes 3 ohm on one way and
7 to 8 ohm on the other way this is normal too only the high MOSFET is left to be checked
which I'll check separately high ohm appears on this way it's an N-Channel MOSFET
so low ohm needs to appear on source to drain ohm is normal here so I couldn't find any short circuit up until now now I need to perform ohm check on +3VSB regulator I perform ohm check on its input (+5VSB) on this pin around 13 ohm appears this pin is output 13 ohm appears on output as input to output values are similar, it is possible that there is a short circuit inside I perform ohm check on input to output, in Analog multimeters,
ohms lower than 3 ohm is suspicious of short circuit that's why I perform ohm check on the other way as well this regulator is most probably shorted I need to remove it and check again there is another double MOSFET in this block which is similar to double MOSFET of RAM VCC this one is double MOSFET of USB VCC I perform ohm check on this one too the upper MOSFET is a P-Channel MOSFET on this way (because it's a P-channel MOSFET),
low ohm appears on drain to source high ohm needs to appear on the other way yes this one is an N-Channel MOSFET low ohm appears on source to drain high ohm needs to appear on the other way yes only the regulator has a problem so far now CPU VCC is left to be checked CPU VCC is made up of many PWMs and MOSFETs I perform ohm check on them one by one first I check 1.8V of CPU, for which I need to check this MOSFET first low ohm needs to appear on source to drain (on one way)
and high ohm on the other way yes this shows that this MOSFET is most probably
Neither shorted NOR disconnected!!! and here I have Op-Amp to check pins 1, 2, 3, 5 and 6 needs to be ohm checked to the GND, to see if they are shorted or not yes
good ohm! I check pins 5 & 6 to each other
and 1, 2, 3 to each other to see if they are internally shorted to each other or not this Op-Amp is OK let's perform ohm check on this block first I perform ohm check on GFX Core to GND
on drain pin of low MOSFET first I perform ohm check on GFX Core to GND
on drain pin of low MOSFET just like RAM block, I make sure of the health of consumer, PWM, and low MOSFET so I perform ohm check yes
good ohm appears ok there is no need to perform ohm check on the other way only high MOSFET is left to be checked for which, high ohm needs to appear on this way and low ohm on the other way yes the next PWM is VCore (VCCP) I perform ohm check on it now good ohm appears on low MOSFET to GND low ohm needs to appear on high MOSFET to the pins on this way higher ohm needs to appear on the other way everything is OK here I can check VCore in here but since I checked VCore and they are parallel,
there is a low chance that there is problem in here but I'll check again I perform ohm check on drain of low MOSFET to GND good ohm appears and I perform ohm check on high MOSFET from both ways low ohm appears on this way and higher ohm appears on the other way (drain to source) this is the high MOSFET of the other choke yes high ohm appears on this way
and low ohm on the other way these are all normal here I have another choke,
let me check that too good ohm appears here too let me check the last choke good ohm appears on this way of this MOSFET yes this is normal too let me check its high MOSFET there is no short circuit here
and it's not disconnected one MOSFET is left to be checked
which provides the CPUSR VCC using this Op-Amp I already checked Op-Amp I only need to check this MOSFET it is an N-channel MOSFET low ohm needs to appear on source to drain on this way higher ohm needs to appear on the other way yes I checked this motherboard's power block only +3VSB has problem I need to change this regulator and the problem of this motherboard will most probably be solved
by changing this regulator! to make sure that input to output is not shorted, I check this with digital multimeter I perform ohm check on input to output pin 0 ohm appears now I'm sure that input to output is shorted there is a MOSFET inside this regulator IC that MOSFET is probably shorted internally so I change the regulator IC and see if motherboard problem gets solved or not I want to change the burned regulator IC now I got a similar regulator IC from a scrap motherboard
you can see it here I got a similar regulator IC from a scrap motherboard
you can see it here mine was UP7706 this is UP0104P I checked them on Datasheet
they match each other and they don't differ much so I remove regulator IC from the mainboard make sure you cover the surrounding components
with heat resistant tape so they won't get damaged or burned!!! and after removing regulator IC, make sure to check and see if the short circuit is solved or not make sure to check and see if the short circuit is solved or not I removed the regulator IC I put it away I perform ohm check on input to output it was shorted before now there is no short circuit on the motherboard I'll check the regulator IC as well I need to perform ohm check on pin 3 to pin 6 those are the input and output pins as you see,
regulator IC is shorted from inside there is a MOSFET inside the regulator IC and that MOSFET is most probably burned pay attention to the direction of this regulator IC place the pin 1 of the IC on the marked place on motherboard when placing the regulator IC, if pins were not tinned enough, apply tin on them again
using Soldering Iron and flux!!! be sure to clear the flux from motherboard afterwards I place the IC here I check Standby voltages on the motherboard there is +5VSB on this way and +3VSB on the other way so I placed CPU and RAM on the motherboard I connected VGA cable I switch ON the motherboard as you see,
we have the display most motherboard problems are related to power block if you professionally learn about motherboard power block,
you can easily repair most motherboards hope this video was useful ;) Produced by: Dr-Bios.com
