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Fans work /no post - black screen

By sickster
Sep 20, 2007
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  1. Firstly my front usb's stopped working for a day, no other problems at all b4 this.

    Then i was away for a few days (computer off) on return computer would not boot. no beeps. no post, just fans and black screen.

    I tested the two ram modules and both have some led lights, i tried taking one out/ then swapping them etc no difference.

    I thought then it was the mobo, i replaced it w a (untested) secondhand mobo.
    This time fans start for a moment then stop, still no post no/black screen etc.

    I tested the power supply in another mobo/old sys and it powered up and there was post sound.

    I have now found that the fans work when the 4pin atx12v is not plugged into the board. as this powers the chip i am wondering if the chip is fried or if it may be something else?
  2. sickster

    sickster TS Rookie Topic Starter

    more info:

    I have also replaced the power supply with 600w jeantech

    also i have since tried to disconnect all power to all but the mobo and 4pin atx 12v - still same problem

    i have removed all the pci cards and graphics card - still no joy

    So what do i have left to do? disconnect any other drives completely and check for poss shorting of mobo?

    The cpu and ram have been reseated when i replaced the original mobo

    any help much appreciated

    why do fans work when atx 4pin is not connected but not when it is connected?

    obviously the system will not post w this disconnected but why do the fans run?

    thanks
  3. Tedster

    Tedster Techspot old timer..... Posts: 10,074   +13

    have you tested your ram?
  4. edddder

    edddder TS Rookie Posts: 19

    pls check also your video card is properly inserted (if you are using one)
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