MSI MS-6760 VER:1 shorted

[s_henya]

Hey guys,

got this media center pc today MSI MEGA 651,
with no power
tried different known to be good power supply but the same.

i can hear that there is a short somewhere but i have no succsess in finding
shorts on pc mainboards. (replace caps usually)

all caps looks good, checked all big ones for esr, tested good.

maybe some refrence about voltage checks or possible shorted elements,

[c_hegge]

Re: MSI MS-6760 VER:1 shorted

Try it with the 4 pin 12V connector unplugged. It won't POST that way, but if it powers on, then you know you have a shorted MOSFET in the CPU VRM.

[ben7]

Re: MSI MS-6760 VER:1 shorted

Try it with the 4 pin 12V connector unplugged. It won't POST that way, but if it powers on, then you know you have a shorted MOSFET in the CPU VRM.

if that is the case, hopefully it hasn't taken any CPUs with it!

[c_hegge]

Re: MSI MS-6760 VER:1 shorted

^
It doesn't usually. I've fixed and replaced boards like that before. 9 times out of 10, the CPU survives. It's not usually a short that feeds 12V directly to the CPU, but rather, a short between the 12V input and ground, which just trips the PSU.

[s_henya]

Re: MSI MS-6760 VER:1 shorted

thanks for the reply
i will give it a go as soon as i get home.

by the way what usually is the fault,

i had a couple of mainboards with the same problem
but i never found the culprint, hope this one wont get to the recycling site.

[s_henya]

Re: MSI MS-6760 VER:1 shorted

still shorted even only with the 20 pin connector,

more ideas..?

[c_hegge]

Re: MSI MS-6760 VER:1 shorted

That rules out the CPU VRM. Try probing some of the pins on the ATX Connector with the resistance test on a DMM. See if any of them are sharted to ground. THe easiest way to do this is to plug a PSU into the connector, leave the black pin connected to ground, and use the red pin to probe one red (5V), one yellow (12V), and one orange (3.3V) Wire. That might give us more of an idea of which area of the board the short is on. Otherwise, you're going to have to start testing the MOSFETs on the motherboard.

[s_henya]

Re: MSI MS-6760 VER:1 shorted

that's odd i cant find that short anywhere,
none of the mosfets are shorted, and none of the 20 pins are shorted to the ground (exept of the blacks)

whats weird is after i dissconnect the power the chipset's fan starts running for a spin or so.