Service manual for Asus Z97-P Motherboard - Have direct short on 3.3V rail!

[elliottveares]

Hi all, does anyone know if it possible to obtain a service manual for the Asus Z97-P Motherboard.

This motherboard of mine died about 6 months ago and on closer inspection today, it turns out their is a direct 0 ohm shot on the 24 pin ATX power connector between pins 24 (Ground) and Pins 12 (+3.3V) and 11(+12V). I have already removed the CPU, RAM, Button Cell Battery before testing; and all of the CPU socket pins are good as far as I can tell.

Want to find the quickest way to determine what is causing this short without having to pull every single component of one by one in a tedious case of trial and error.

Being a densely packed multiplayer board, it is also hard to determine where the ATX pins go to in order to trace them out!


Kind Regards: Elliott.

[Ed.Kloonk]

Check for bulging capacitors.

[coromonadalix]

For a problem like this, at my job,  i put an psu on the shorted line and use an Flir  thermal camea and i can find the problem relatively fast ......  but the flir  cost around 1k$   outch

I had defective smt  power supply mosfets,  they where a nightmare to remove even with propers tools.


Sorry to say : you'll probably never find an motherboard service manual, unless it was leaked on the web ...

[DaJMasta]

Service manuals for boards like this effectively don't exist.  Visible damage on caps or switching mosfets is a good starting point - if your ohmmeter is sensitive enough, you should see a slight dip in resistance when you are closer (in terms of trace distance) on the board to where the issue is.


Agree though with the thermal camera, would make short work of finding a short.  Alternatively you can use your finger to find a part that goes warm or hot within moments of power on, or even put little drops of IPA on suspect chips and seeing which cooks off faster when powered on.

[Rasz]

For a problem like this, at my job,  i put an psu on the shorted line and use an Flir  thermal camea and i can find the problem relatively fast ......  but the flir  cost around 1k$   outch

Seek compact ~$250
https://store.ipadrehab.com/Seek-Compact-Thermal-Camera-p156667222
or pr0 ~$450
https://store.ipadrehab.com/Seek-Compact-PRO-High-Resolution-Thermal-Camera-p146857160
+ macro lens (no, you cant use cellphone macro lens hehe) $50
https://store.ipadrehab.com/Macro-Lens-for-Seek-Compact-and-CompactPRO-Thermal-Camera-p146857762

for non cellphone stuff cheaper compact is just fine

I had defective smt  power supply mosfets,  they where a nightmare to remove even with propers tools.

its a breeze with preheater and non shit air (861). People try paint strippers, $50 chinese 858 stations, or Hakko 936 type clones based on design contemporary to Churchill and get into trouble.

Sorry to say : you'll probably never find an motherboard service manual, unless it was leaked on the web ...

True. Iv personally only got my hands on at most Z87 board diagrams (GIGABYTE GA-Z87-DS3H), havent seen any asus/asrock, or anything more modern yet.

and yes, people do fix modern'ish motherboards:

[TheMG]

Schematics for desktop computer motherboards are near impossible to find compared to laptop schematics.

A crude (but sometimes very effective) method of tracing down such shorts is to hook up a current limited bench power supply to the shorted rail, and start cranking it up until (hopefully) something gets warm.

If it's a very low impedance short it's unlikely to be a short within a logic IC. Probably a shorted MLCC somewhere on the board.

All this being said there really isn't a whole lot on modern motherboards that use the 3.3V rail. You can look up datasheets for the various ICs on the board to get an idea of where the 3.3V goes on the board. 3.3V does go to a few pins on the PCI-express slots and there is most certainly going to be bypass capacitors associated with those pins, and the pinout of PCI-express connectors is well documented, so that's another place to start.

[mariush]

3.3v may be used by the memory vrm (the dc-dc converter which creates 1.2v...1.5v for ddr3/ddr4  - check the controller and the mosfets maybe one is shorted.

There's 3.3v going to the pci-e slots and it may also be used to produce 2.5v or 1.8v using LDOs for the onboard sound chip.

I'm a bit concerned about the claim that there's short between ground, 3.3v and 12v pins... the 24pin connector has multiple 3.3v pins and 2 12v pins ... the pins should be connected to the same "islands" so if there's a short between pin 12 3.3v and pin 11 (12v) shouldn't you have short between pin 11 and all the other 3.3v pins?

Anyway, motherboards have 4+ layers, usually 6 or even more... there's big copper fills in the inner layers carrying voltages around the board, can't really trace from pin to components.

You could just try to push 3.3v with a current limit (start with 100mA, then go up) and see if any component warms up ... use your finger, or maybe some isopropyl alcohol on the chips and see which evaporates faster.


 

[kripton2035]

something like this : http://kripton2035.free.fr/Continuity%20Meters/continuity-elv.html
or this : http://kripton2035.free.fr/Continuity%20Meters/continuity-short.html
will help you find a short on a pcb.

[elliottveares]

Thanks for the reply's everyone, unfortunately I don't see any bulging caps on the board or any other clearly failed components.

I might have to apply the appropriate power to the voltage rails and try and find if anything is heating up. Thing is all I have to currently work with is a Basic Hako FX-888D solering iron, a basic manual ranging multimeter with a K type thermocouple, and a inferred laser thermometer.

mariush, regarding your concern, it is like all 3 pins mentioned in my original post are commend together! (i.e. There is a short between Ground pin and 3.3V pin, a short between ground pin and 12V pin, and short between 3.3V pin and 12V pin!)

kripton2035, that's a good idea; do you know of any of the shelf ELV short circuit detectors.

Oh and Happy 2020 for those in the land down under.

[magic]

If both rails are shorted to ground then both are shorted to each other. Obviously

That being said, not a good situation.

Could it be a crapped out PSU taking the mobo with it?

I'm pretty sure Louis Rossmann had some videos on guerilla methods for finding shorted components on computer boards.

[kripton2035]

kripton2035, that's a good idea; do you know of any of the shelf ELV short circuit detectors.

I bought the elv kit, works fine. I also build the shorty device, works fine too, although I have some bad soldiers or contacts on the protoboard that make it not so reliable.