Industrial Computer Problem

You possible have a bad bios chip (or the stuxnet virus).

Is there a CMOS data retention battery? That's the first I would check. S.M.

Dear Sir,

Yes Battery is already installed CR2032. kindly check back plane & CPU board pictures

Having ONLY the CPU board, memory, monitor and keyboard attached, remove battery, find jumper 8 (JP8) on CPU board,short it for a few seconds, reinstall battery, and try to boot while pressing Del (not the cat) on the keyboard. If all is OK you will boot to bios. Have you messed with any other jumpers? S.M.

I had a PC in for repair two weeks ago with a similar fault, the CPU fan switched on for 1 second then nothing. This unit had a main 20 pin PSU connector and a small 4 pin plug supplying 12Vdc to the mother board. There was a dead short circuit across the 12V line on the mobo and the PSU shut down immediately.

Checked the 12V tracks on the mother board and found a blown MosFet chip and 3 electrolytic capacitors which were 'swelling' at the tops. I replaced the Mosfet and the capacitors and everything worked again. Can only assume the capacitors were starting to draw excess current and this took out the Mosfet - or - it could have been something external to the mother board such as a bad USB connection.

Dear Sir,

Thanks for your guide line. I will check your said procedure & back to you.

Regards,

Dear Sir,

I have done following step as per your advices,

1- OPEN BATT & CLEAR CMOS. NO CHANGE

2- CONNECT POWER SUPPLY DIRECT WITH ROCKY. NO CHANGE

3- check & trace +12 volt line which is comming from CN3 pin10 & going to IC U23 PIN24 & C3 capacitor. NO CHANGE

4- Kindly tell me which capacitor & MOSFET you have to replaced?

Please advice,

Hi Ahmadarshad,

I have had this fault before, have a look at the board, are the electrolytic capacitors buldging at the top? If this is the case you may need to replace them, I haven't had much success in doing this because the fault is normally not only the caps but also transistors or IC's in the sub-section that got effected by the capacitor shorting out due to the electrolyte in them drying out. Trying to find the equilivent components is a mission if you dont have schematics. If you are lucky it will be the output transistor as previosly mentioned, this can be tested in circuit as normally shorts out between all the gates, you should get a junction drop of about +-0.7V between emmitter and base and collector and base, check the datasheet for it on www.alldatasheet.com, to be sure clip the legs off and test it, then solder them back together, trying to de-solder it is tricky if you are not used to soldering gold plated multi-layered boards.

I would suggest looking on E-Bay for the same board, they are normally quite cheap. Also check your towers fans and ventilation, electrolytic capacitors have a lifespan unlike other passive components because of their construction using electrolitic paste between the foil and paper in the roll, this will dry out eventually and short the cap out. I have made it a rule of thumb for my guys to replace all the caps every two years or so, or if they do any repairs to boards, this saves alot of issues in the future.

The number you need to search for is written on the board, try search for that on E-Bay.

Hope this helps,

Rob.

Dear Sir Robo,

I have read your guide lines & I will replace all of elect capacitors & try to open MOSFET legs one by one to fine our short circuit between them & back to here.

Thank to all my forum respective memberz

Dear Sirs,

I have arranged one desktop spare power supply & confirmed that my board is OK & also surprised that original power supply giving right voltages on every pin as per data sheet but when connect NO WORK why?

Sir, Please share your experiences with me.

POWER SUPPLY DETAILS.

BRAND SEVENTEAM

MODEL ST-250UAG-05E

+3.3V=17A

+5V=20A

+12V=18A

-12V=0.5A

+5VSB=2A

PS-ON=REMOTE

POK=P.G

COM=RETURN

It saw you coming and put an end on its life.