Replacing OST caps on Microstar KT6 Delta motherboard

[Agent24]

Re: Replacing OST caps on Microstar KT6 Delta motherboard

So, does that mean that the thermal protection IC connects the terminals either side of where resistor R44 would have being?
Would it be a good idea to put a resistor in that gap and see what happens?
Or is there a more sensible/safer approach?

Yes it connects where R44 would go. The schematic shows R44 as "X_0" - the X likely means "not stuffed" (stuffed means 'put on the board') and 0 probably means it would be 0 ohms normally, which makes sense.

You could put a resistor in for testing purposes (You would of course lose CPU overtemp protection) but you would need to disconnect at least the output pin of U1 to avoid backdriving the output and damaging it (U1 might be perfectly OK, we don't know yet)

The Voltages on that chip U1 are as follows:
1 PW_DN: 5.01
2 GND: to Ground
3 PS_IN#: 0.61
4 TMP-D+: 0.79
5 TMP-D-: 4.46
6 PS_OUT#: 4.93
7 VREF: 4.75
8 5VSB: 5.01

Pushing the power button once, and then rechecking, did not change any of these values.

Sorry, I meant check voltages between when the button is not pressed and when it is held down, not when it is pressed and then released.

[Sparkey55]

Re: Replacing OST caps on Microstar KT6 Delta motherboard

I think your Southbridge chip is working ok based on what is being indicated by the leds for the hardware. Have you checked to see if the CPU heatsink is flat on the CPU? Does it still get hot?

[Sparkey55]

Re: Replacing OST caps on Microstar KT6 Delta motherboard

In post #53, I think, you said that the CPU got hot. How hot did it get and what did you use to determine the heat; your fingers on the heatsink or something else?

[socketa]

Re: Replacing OST caps on Microstar KT6 Delta motherboard

Yes, i have tried that - No keyboard has being connected throughout this testing

[Sparkey55]

Re: Replacing OST caps on Microstar KT6 Delta motherboard

Have you tried to start the computer with no keyboard connected?

[socketa]

Re: Replacing OST caps on Microstar KT6 Delta motherboard

Shorting the green wire (on the PSU) to ground, causes the CPU fan to spin, but no BIOS Beep, or video signal.
The HDD and power LEDs turn on.

The part number written on the U1 chip is Attansic ATTP1.

Looks like a thermal protection IC which will shutdown the system if the CPU overheats, see THERMDN and THERMDP lines on Page 5.
It intercepts the PS_ON signal from Q6 to the PSU. Since we know Q6 works, problem could be U1 or one of its support components.

So, does that mean that the thermal protection IC connects the terminals either side of where resistor R44 would have being?
Would it be a good idea to put a resistor in that gap and see what happens?
Or is there a more sensible/safer approach?

The Voltages on that chip U1 are as follows:
1 PW_DN: 5.01
2 GND: to Ground
3 PS_IN#: 0.61
4 TMP-D+: 0.79
5 TMP-D-: 4.46
6 PS_OUT#: 4.93
7 VREF: 4.75
8 5VSB: 5.01

Pushing the power button once, and then rechecking, did not change any of these values.

[Agent24]

Re: Replacing OST caps on Microstar KT6 Delta motherboard

Looks like a thermal protection IC which will shutdown the system if the CPU overheats, see THERMDN and THERMDP lines on Page 5.

It intercepts the PS_ON signal from Q6 to the PSU. Since we know Q6 works, problem could be U1 or one of its support components.

[momaka]

Re: Replacing OST caps on Microstar KT6 Delta motherboard

Well, it just dawned on me... but maybe try to see what happens if you short the green wire on the PSU ATX connector to ground while the PSU is plugged in the motherboard (along with the 4-pin CPU plug).

Because this resistor is not present, i want to find out what component sends PS_ON to ground, to start the PSU.

Well, let's start at the front panel power button. In the schematic, it is connected between ground and PWBTIN#. PWBTIN# goes to pin 1 on U1 (ATTP1/2??? not sure what this IC is) - see page 41. My guess is that U1 then controls signals PS_IN# and PS_OUT#. But I am not sure what that U1 IC is. C an you post what part number is written on it?

PS_ON is also connected to PW_OK via a resistor , a transistor and a schottkey rectifier.

You can ignore that, because PW_OK only matters *after* the PSU has been turned ON via PS_ON signal.

[socketa]

Re: Replacing OST caps on Microstar KT6 Delta motherboard

This is still sitting on the desk, so thought to have another crack at it - since all that other testing appeared to be ok
The power switch is activating a transistor Q6 (page 43) that would send PS_ON to ground (except that resistor R44 is missing, and was never there in the first place)
The transistor is working, as the voltage at the collector? drops from 3.39V to 0.78 or 0.6 when the power switch is pushed, and the base? jumps from 0V to 0.079V
Because this resistor is not present, i want to find out what component sends PS_ON to ground, to start the PSU.
PS_ON (and 5VSB via a resistor) is connected to PS_OUT# which goes to an Over Temperature Protection Controller Chip

PS_ON is also connected to PW_OK via a resistor , a transistor and a schottkey rectifier.

Any more clues?

[socketa]

Re: Replacing OST caps on Microstar KT6 Delta motherboard

Gosh, i really need to sharpen up, and watch out for dyslexia (which, IMO, is really not just paying enough attention)
Not sure if it happened while reading it, or during the transition to writing it down.
Or perhaps i got distracted by that buzzing noise, and it was past bed time.
Note to self : Next time you see 2_5 and get a 'reading' of something 2.15, recheck it.
Sorry 'bout that

Rechecked VSUS2_5, and it was 2.51V - not 2.15V
So looks like it's meant to be on.

The voltages at that op-amp U12 are:
Pin (3 & 5) (VREF) = 1.25V
Pin 8 (9VSB) = 9.67V
Pin 2 = 1.26V which goes to resistor R245, and other side of this resistor has 2.51V (VSUS2_5)

I can see, however, that when the PC is running, that "9VSB" becomes 12V because of diode D11.

Does that mean that it becomes a 12V serial bus, or is it still a 9V serial bus with 12V on it?

[momaka]

Re: Replacing OST caps on Microstar KT6 Delta motherboard

Am assuming that you meant page 42?
(Just checking that we are looking at the same document)

EC14 has 3.3V on it
And EC36, which is connected to VSUS2_5 (page 42) has 2.15V on it

Ah yes, page 42 indeed. (I did it again! Thinking of one thing and typing another. Maybe I need to start taking )

Anyways... So with 3.3V on 3VDUAL, then the SB (VT8235) is at least getting power there.

Now, that voltage you got on VSUS2_5 seems a bit low. You should get +/-5% at the most. So that's 2.375V for the lower limit. I don't know if that is indicating problem with something pulling too much power from VSUS2_5, thus causing it to sag, or if the LM358 (U12A) is bad (or maybe some voo-doo black-magic causing your multimeters to be off?... even though we already checked that they work right in the ASUS P5VDC motherboard thread). I guess you should check the reference voltage (VREF1_25) on that LM358, pin #3. I think VREF1_25 is generated by that MSI-5 ACPI controller.

Also, while looking at that LM358 op-amp, I kind of wonder what voltage does "9VSB" have. It seems like another voltage generated by that MSI-5 IC. I can see, however, that when the PC is running, that "9VSB" becomes 12V because of diode D11.

All of this is on page 42, by the way (both for my reference and yours)

VCC2_5 (same page) is connected to EC31, which has 0V on it.

Well, I will only *guess* that VCC2_5 is meant to be off, since we do have 2.5V on VSUS2_5 (well, not quite, but it still counts, I suppose).

Something that may, or may not, be worth mentioning:
When i was checking EC14 +VE to ground, i heard a noise like a small fly that had being hit with fly-spray when it's spinning on its back, and it stopped as soon as i removed the probe
When i tested it again, there was no noise
No smoke or smell.
I had the backside of the board vertical, and towards me, and the PSU and CPU fan on the other side, so they were obscured from view. Swapped the CPU fan just to see if that was causing a fault - but changing it made no difference.
No flys or fly-spray in the house.
Possibly just a fluctuation of the quantum vacuum?

I'll go with that last one. I literally have no clue what could have happened there . Still, observations like that are always worth noting nonetheless, as that implies you are a careful tech with attention to detail.

I sometimes get quite annoyed (and eventually amused too) by having to fix something after other careless "tech" had worked on it. If I see missing or misplaced screws, that's usually a good hint of what to expect .

[socketa]

Re: Replacing OST caps on Microstar KT6 Delta motherboard

Appreciate you checking that out, and the explanation.

VSUS2_5 is derived from 3VDUAL through Q39. (Page 39 bottom.)

Am assuming that you meant page 42?
(Just checking that we are looking at the same document)

EC14 has 3.3V on it
And EC36, which is connected to VSUS2_5 (page 42) has 2.15V on it

Same goes for VCC2_5 as for VSUS2_5.

VCC2_5 (same page) is connected to EC31, which has 0V on it.

Something that may, or may not, be worth mentioning:
When i was checking EC14 +VE to ground, i heard a noise like a small fly that had being hit with fly-spray when it's spinning on its back, and it stopped as soon as i removed the probe
When i tested it again, there was no noise
No smoke or smell.
I had the backside of the board vertical, and towards me, and the PSU and CPU fan on the other side, so they were obscured from view. Swapped the CPU fan just to see if that was causing a fault - but changing it made no difference.
No flys or fly-spray in the house.
Possibly just a fluctuation of the quantum vacuum?

[momaka]

Re: Replacing OST caps on Microstar KT6 Delta motherboard

Think that i found the rail that powers the South Bridge
The MSI schematic shows that the VCC33 pins of VT8235 (the one on this 2.0 version board is VT8237) is connected to an electrolytic capacitor, EC44 - and there is no voltage present there

VCC33 on the VT8235 in the schematic connects to VCC3. And if you look at the ATX connector on page 43, you will see that VCC3 is the 3.3V rail on the PSU. Since the PSU is not turned ON, then there would be no VCC33 going to the VT8235.

That said, the VT8235 has two other type of power pins: VSUS25 (which connects to VSUS2_5 on chematic) and VSUS33 (which connects to 3VDUAL point on schematic) - as given on page 18 and 19. Check what voltages you get for these two.

3VDUAL can be found on capacitor EC14 (supposedly a 1000 uF, 10V cap), and is generated either by Q16 when system is powered OFF/standby or Q25 when system is ON. (Page 42 bottom.)
VSUS2_5 is derived from 3VDUAL through Q39. (Page 39 bottom.) However, I am not sure if VSUS2_5 should be present without the PC being powered ON. Therefore, I think only 3VDUAL should have 3.3V on it at all times, regardless of what state the PC is in.
Same goes for VCC2_5 as for VSUS2_5.

[socketa]

Re: Replacing OST caps on Microstar KT6 Delta motherboard

3.28v

[Agent24]

Re: Replacing OST caps on Microstar KT6 Delta motherboard

https://en.wikipedia.org/wiki/Low_Pin_Count

Do you get something between 3-5v on the PWSW+ connector at front panel?

[socketa]

Re: Replacing OST caps on Microstar KT6 Delta motherboard

No, the fans do not twitch - they remain absolutely still.
Yes, have tried resetting the CMOS several times now - with, and without, the battery.
The jumper was returned back the "Keep Data position"

There is voltage on the PSU green wire of 4.97V
5VSB : 4.98V

Winbond W83697HF LPC chip:
VCC Pin 5 = 0V
VCC3V Pin 22 = 0V
VSB Pin 99 = 4.98V
VBAT Pin 102 = 3.60V
AVCC Pin 105 = 0V
(Just noticed that there is dots on the board that aid in the counting of the pins - that makes things a lot easier)

Think that i found the rail that powers the South Bridge
The MSI schematic shows that the VCC33 pins of VT8235 (the one on this 2.0 version board is VT8237) is connected to an electrolytic capacitor, EC44 - and there is no voltage present there

Also checked the voltage at the Bios Jumper, and get 3.60V to ground

P.S. What is meant by low pin count? - obviously, it's not referring to the number of pins.

[momaka]

Re: Replacing OST caps on Microstar KT6 Delta motherboard

Now the motherboard doesn't respond when the power button is pressed (no CPU fan and CPU cold)
Checked that the CPU was OK in another motherboard - yep OK
Removing the 12V CPU plug makes no difference

Something is stopping the power button from starting the PSU
There is 3.3V on the power button positive pin.
On the ATX female connector, there is 254 ohms to ground on the 3.3V rail.
i compared with a couple of other MSI socket A boards and there was no connection to ground whatsoever on the 3.3V rail.
So perhaps this is a hint as to what is causing the problem?

Odd that it was half working, until i reset the BIOS.

Do any of the fans in the PC twitch or move for a second when you press the power switch?
- If yes, you have a short-circuit somewhere. That 254 Ohms to ground on the 3.3V rail could be it.
- If no, rest CMOS again. maybe even try without CMOS battery. Also check your CMOS reset jumpers - if you forgot it in the reset position, the motherboard may not boot. Lastly, check voltage going to the Southbridge and LPC/Super IO chip.

[socketa]

Re: Replacing OST caps on Microstar KT6 Delta motherboard

Removed the other choke, and then tested the other (non-VRM) side of the chokes to ground:
27 ohms with no CPU installed
4 ohms with cpu installed

Looking at the pictures for this board, I don't see a separate buck circuit for the Northbridge, so it is possible this is one of those few boards that powers its Northbridge from the CPU V_core rail. Therefore, don't be alarmed if the "lower" MOSFETs appear shorted even with the CPU removed.

So, that 27 ohms is possibly quite normal.

Pulled a choke from an artifacting nividia video card, which had same size toroid and number of turns, but slightly thicker wire, and used that to replace the one that i destroyed.
Tested the caps, and they all had good capacitance and ESR - so put them back in.
Re-soldered the VRM mosfets, since they were not shorted, and tested in agreement with the schematic (also noticed that the output mosfets are paralleled with another pair that are not on the schematic)

Put the CPU and heatsink back on, and connected power supply.
Pushed power button and the CPU fan was spinning and the keyboard flashed it's lights as normal.
CPU got hot
Also the green front panel power LED lit up
Checked the voltage to the CPU it was 1.68V which seems about right power for a Barton 462 processor (Spec = 1.65V)
But that was it, - no beep, or boot into BIOS
Powered off with power button

Tried again several times - No change
So turned it off, cleared the CMOS with the jumper (just in case that was causing the problem)

Now the motherboard doesn't respond when the power button is pressed (no CPU fan and CPU cold)
Checked that the CPU was OK in another motherboard - yep OK
Removing the 12V CPU plug makes no difference

Something is stopping the power button from starting the PSU
There is 3.3V on the power button positive pin.
On the ATX female connector, there is 254 ohms to ground on the 3.3V rail.
i compared with a couple of other MSI socket A boards and there was no connection to ground whatsoever on the 3.3V rail.
So perhaps this is a hint as to what is causing the problem?

Odd that it was half working, until i reset the BIOS.

[socketa]

Re: Replacing OST caps on Microstar KT6 Delta motherboard

Thanks, momaka, for the advice, and the offer to send the parts.

Yes, i thought about re-gluing the broken section, but only after throwing it out.
Doh!

Will first overcome a reluctance to deal with humans, and fear of rejection, and go to the waste recycle depo and ask if i can have a scrounge.
That makes a lot more sense, than you posting parts.

Will post back here when i have put the new caps and chokes on.

Cheers

[momaka]

Re: Replacing OST caps on Microstar KT6 Delta motherboard

Might even temporarily just use the old broken choke - as i'm thinking that it should still work, even if a section of the bottom of the ferrite?

No, you can't use that choke with the broken core. Any time you introduce or increase the air gap in a core, that changes the inductance. If you had all of the peices from the broken choke and you glued them back very tightly, the inductance may or may not change too much, and the motherboard *might* just work, but I still would discourage you from doing that (unless you feel experimental ). Though I doubt anything major is going to happen if you mismatch the inductance - most likely the voltage regulation will be off and the motherboard will refuse to boot.

Anyways, I checked my stash... and all I have is 4-turn chokes from Xbox 360s. Don't know what inductance they are, but the turns are made from three thick wires, so at least they should be able to handle the current.
I also have 1.2 uH chokes from an ASUS LGA1156 motherboard (they are on CPU VRM), though I don't know their current-handling capability and they look a bit small.

I guess if you can't find anything, let me know. I can either pull out and send you those 1.2 uH chokes or I can send you the 4-turn chokes from the Xbox 360s and you can either re-wind them with 5-turns with the wire you have from your broken choke or you can use the 4-turn chokes as-is (in that case, you must replace both on your motherboard, becase it would be better if they match).

I also have MOSFETs and caps - again, Xbox 360 pulls, but they are all working. Could send them with the coils.