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dicky96 03-25-2020 08:29 AM

Asus Prime Z270-P no Vcore
3 Attachment(s)
Hi guys

I have an Asus Prime Z270-P.

With no CPU fitted it will not start

With a Celeron G3900 CPU it starts but the CPU is cold and I have no Vcore

12V to the 8 pin molex is good, as are 12V, 5V, 3.3V to the ATX connector

Checking with a scope I have no drive to the high side gate of the Vcore MOSFETs, the gate is 0V. I didn't bother check the low side.

The MOSFET are M3054M

There is this chip uP1540P near the MOSFETs. Each high side FET has one pin of an 820R resistor connected to the gate and some of theee resistors then connect to one pin on the uP1540P but not all of them. The ones that do all connect to the same pin on uP1540P. I can't find a datasheet for uP1540P.

Also there is this other nearby QFN ASP1400BT that I think is the controller for the Vcore PSU, there look like 7 phases. But I can't find a datasheet for that either.

I do have a 1.2V supply near the DIMM slots which is probably Vram and that is running OK.

Looking for a board view plus datasheets for uP1540P and ASP1400BT plus any helpful advice on diagnosing the fault

It looks like there is a board view on a paysite which also has the MS6178 schematics I need for another repair so I may have to pay there :o:


piernov 03-25-2020 09:29 AM

Re: Asus Prime Z270-P no Vcore
That would more likely be something like 4 Vcore + 2 VCCGFX + 1 VCCSA. Check if you get something on any of the inductor as VCCSA has to come up before the others. There should also be a VCCIO that comes up before VCCSA.
No damage inside CPU socket? CPU VCore not shorted to ground?

SMDFlea 03-25-2020 10:12 AM

Re: Asus Prime Z270-P no Vcore
i found a pinout for the uP1540P

dicky96 03-26-2020 09:06 AM

Re: Asus Prime Z270-P no Vcore
2 Attachment(s)
Hi guys
I don't think that pinout is the same as my device as it only has 10 legs unless there are some pads underneath it. It's a bit of an odd shaped package, I don't know that that is called.

Anyway I have 12V on what I assume is pin 1 (nearest the dot) and 0V on all the other pins

All of the 7 phase coils have 0V on them


dicky96 03-26-2020 09:54 AM

Re: Asus Prime Z270-P no Vcore
How did that thumbs down icon get on this thread?? If I pressed a wrong button then ooops!

piernov 03-26-2020 11:05 AM

Re: Asus Prime Z270-P no Vcore
There's probably a center pad connected to ground.

What's the voltage on the inductors near the PCH?
And the ones near the RAM?

dicky96 03-26-2020 11:59 AM

Re: Asus Prime Z270-P no Vcore
1 Attachment(s)
Yes some centre ground pad = pins 11/12/13 there is because I now have the board view :wink:

I don't have any Vcc to the uP1540P

This should help

dicky96 03-27-2020 07:55 AM

Re: Asus Prime Z270-P no Vcore
1 Attachment(s)
OK I took some voltages on the Colis and a few Power FETs

+5VSB DUAL 4.98V

VDDQ 1.212V

P+2V5 SW 2.510V

P +1.0V A SW 20 1.032V
P1.0V A 1.022V

+12V CPU 12.18V
P VCORE L +12V S 12.18V

PL1010 / PL1020 / PL1030 / PL1040
P VCORE PHASE 1/2/3/4 20 OV

PL1310 / PL1320
P GT PHASE 1/2 20 0V


PU1511 (uP1540P)
All other pins 0V

Now here is the interesting thing...

uP1540 pin 8 is P VCCSA POK and its 0V. This comes from a resistor PR1063. The other end of PR1063 P VCORE EN 10 connects to pin 2 of PU1000 (ASP1400BT) and this is 2.027V.

But this is because the resistor PR1063 is missing from my board and as this looks like it is the enable pin for uP1504P I don't see how it could work without it! Also the soldering here looks 'shiny' like maybe someone has been messing. The same with capacitor PC1509, which is missing, and which connects from pin 10 of uP1504P (P VCCSA REFOUT 10) to ground - but I don't think that is quite so critical.

The board view says this resistor is MBS_R0402 but a lot of the resistors say the same. I measured PR1596 in circuit which also says MBS_R0402 and that reads 256R

What do think? I should put something like a 270R resistor in there and see what happens? And maybe a capacitor of some value in missing PC1509?

dicky96 03-27-2020 07:58 AM

Re: Asus Prime Z270-P no Vcore
1 Attachment(s)
Wrong pic

This one....

dicky96 03-27-2020 10:33 AM

Re: Asus Prime Z270-P no Vcore
It just occurred to me that MBS_R0402 will be the size of the SMD resistor, nothing to do with the value DOH :duh:

What value to put in there? I don't think it would be critical...

piernov 03-27-2020 01:12 PM

Re: Asus Prime Z270-P no Vcore
That definitely looks to be no stuff.
Check voltage on VCCIO.

dicky96 03-27-2020 05:03 PM

Re: Asus Prime Z270-P no Vcore

Originally Posted by piernov (Post 951015)
That definitely looks to be no stuff.
Check voltage on VCCIO.

Sorry didn't your reply, could you elaborate?

dicky96 03-28-2020 05:47 AM

Re: Asus Prime Z270-P no Vcore
Where is VCCIO I can't find that? Maybe it has another name on my board

There is 3.3V on some of the capacitors integrated onto the north bridge and 1.02V on the others. The north bridge gets warm but not hot

There are no shorts from any of the inductors to ground


dicky96 03-31-2020 04:27 AM

Re: Asus Prime Z270-P no Vcore
YES!! I have a result!

I took a half educated guess and fitted a 470R resistor in place of missing PR1063. I didn't bother with what looks like a missing capacitor PC1509 partly because I don't think it is critical to have the capacitor but mostly because I have no 0402 SMD Caps!

And hey presto she fired up like a good 'un. :rejoice::spin::rejoice:

I attached a HDD with Windows 10 on it, booted windows and I'm online. I used SDI 1.20.0 to install all the drivers and everything looks rosy

Job done!

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