VOGONS


First post, by Roland30

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Hello , i have a FIC PA-2013 motherboard , i wanted to put in a new system, the board was working fine for 30 minutes , after that it started freezing and had to restart to make it work, and made a squeeking noise at the cpu capacitors ( the small SMD capacitors in the middle of the socket )
Now the motherboard wont post at all ...

So basically i identified a mostfet that is really hot, near the battery , its a 9435A -30V P-Channel Enhancement Mode MOSFET.
I uploaded 2 pictures where the hot mosfet is .

What i've done :

Replaced the mosfet with a new one , replaced it again with a new one ( just in case )
Recapped all main capacitors with new ones.
Checked for any short ( ive checked all small smd capacitors , none of them are in short )
Replaced 3 cpu-s
Tried with 2 power suplies
Tried with at least 10 memories
Cleaned the board
North bridge and South bridge look good because i cannot identify any short.
Checked the 2 VRM-S near the CPU , not in short .
Removed all main capacitors like 13 of them and started the board without them ( mosfet still getting hot )
And yes the jumper settings for the cpu are okay.
Checked for any dirt between ( Sdram slots , agp , pci )

So basically i dont have any more ideeas, i will try to start the board tomorrow without the bios chip , and see if mosfet still getting hot , if it wont maybe some problem within the bios chip ? i have a programmer so i can make another bios chip.
Anybody can come up with some ideeas , because i have kinda ran out of them 😀

Come lets ressurect this board , its one of the best motherboards out there if not THE BEST for super socket 7 , it would be a shame for it to die 😀

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Reply 1 of 6, by synrgy87

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Have my FIC VA503+ died in a similar fashion to this I've not been able to get it back up and running again, the failed mosfet could have taken something else out if that's what's failed, although I wasn't able to identify any other shorts or failed components, Could be something SMD. or a dead VIA chip(hopefully not).

Reply 2 of 6, by Roland30

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Oh so i am not alone , i am trying everything i can to make this board up and running again 🙁
I dont think its the chipset , because all components near them are not in short , usually when the chipset dies there are a lot of capacitors (smd) near that are in short.
Oh and also when i start up the board the cpu gets normaly hot ( its getting its default temperatures without a heatsink)

Reply 3 of 6, by verysaving

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The mosfet you replaced, the ic controller near it, the diode,
the coil and the electrolytic capacitor forms a DC-DC converter
that should supply some chips on the board.
You need to check (or replace) the diode and the controller that
drives the mosfet.

This is the datasheet of the controller :

https://www.onsemi.com/pub/Collateral/CS51031-D.PDF

the typical application diagram in figure 1 should give you
an idea of how it works.

Keep in mind that usually a mosfet blows because of an overload,
so most likely, something powered by the mosfet failed short
(or very low resistance) and caused it to blow.

Reply 4 of 6, by Horun

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Roland30 wrote on 2020-11-30, 23:59:
Hello , i have a FIC PA-2013 motherboard , i wanted to put in a new system, the board was working fine for 30 minutes , after th […]
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Hello , i have a FIC PA-2013 motherboard , i wanted to put in a new system, the board was working fine for 30 minutes , after that it started freezing and had to restart to make it work, and made a squeeking noise at the cpu capacitors ( the small SMD capacitors in the middle of the socket )
Now the motherboard wont post at all ...

So basically i identified a mostfet that is really hot, near the battery , its a 9435A -30V P-Channel Enhancement Mode MOSFET.
I uploaded 2 pictures where the hot mosfet is .

Appears that is for the AGP slot. The CPU Mosfets and circuit are near the cpu socket.
You never mention what video card you are using. Does that 'red circled' mosfet get hot when using a PCI card ?
Hard to believe a Mosfet that can handle 5amps does not have a heatsink tab. The PDF says it runs up to 125C on a minimum pad, which it is, and that is very hot !

Hate posting a reply and have to edit it because it made no sense 😁 First computer was an IBM 3270 workstation with CGA monitor. 🤣 Second computer a 286 12Mhz with real IDE drive ! After that came 386, 486, Pentium, P.Pro and everything after....

Reply 5 of 6, by LeFlash

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Mosfets tend to run hotter when the driving signal gets weak.
Then they are in a state between open and short, converting energy to heat.
Best would be to check the gate with an oscilloscope, second best is to just change the controller and diode.

Reply 6 of 6, by Roland30

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Thank you for the quick reply , the diode seems fine when checked in continuity mode on the multimeter , the 51031 its cold when i touch it .
Should i try to replace first the diode , and if its still getting hot , replace the 51031 ic ?