PC warned me about low power and now won't boot

Byron172Byron172 Adelaide, South Australia Member
in Hardware
A couple days ago my Media Centre PC warned me (in POST stage of boot up) that there was a low power issue. When I pressed F1 it then proceeded to boot so I didn't worry about it. Next time I booted it wouldn't boot, but all fans fired up etc but no BIOS etc. In fact the fan on the PSU went into "overdrive" (real LOUD)!! I figured it would be PSU so swapped out but now nothing. Have reset and replaced the CMOS battery, swapped out RAM and took out the Graphics card and used onboard VGA only. Now all I get is LED on mobo is lit and when I press the power button the light comes on only while the button is pressed - as soon as I release the power button the light goes off. No fans, no nothing. Anyone got any suggestions? Could it be that I need a more powerful PSU? (I only have a 250W for testing and the original was 240W). Do power supplies die slowly sometimes? I woulda thought that when they go - they just go.

Comments

  • ardichokeardichoke Icrontian
    Power supplies slowly get less efficient over time (capacitors age and don't work as well as when they were new), it's entirely possible that your old PSU went and your testing PSU is too old to do the job as well. In order to tell if this is the case, we would need to know what all the rest of the hardware in the system is.
  • Byron172Byron172 Adelaide, South Australia Member
    Just plugged in a 400W PSU and it fires up but still no luck getting into BIOS or boot up. BTW - It's actually the processor fan that was going into "overdrive" as it has started doing it again with this more powerful supply.
    The specs are HP Compaq
    Dual core 2 x 3.0Ghz proc.
    4GB ram
    160GB SATA HDD
    ATI Radeon X1300 - 256mb graphics card
    DVD RW optical drive

    (Nothing too fancy as it only needs to play movies and arcade games).
  • Cliff_ForsterCliff_Forster Icrontian
    Everything about it seems like a CMOS battery failure. Double check that new battery if you haven't already.
  • Byron172Byron172 Adelaide, South Australia Member
    I've tried 5 different CMOS batteries (all work in other PCs)
  • Cliff_ForsterCliff_Forster Icrontian
    I'm almost sure the CMOS chip has failed.
  • RyderRyder Kalamazoo, Mi Icrontian
    It sounds like part of the PSU you had in the machine "gave up" and could not supply the current necessary to a component. When that happened, the component failed because the the current was too low. It basically burnt up.
  • Byron172Byron172 Adelaide, South Australia Member
    edited January 2014
    Bought a second hand PC same as this one and tried the old CPU in it and the alarm went off and just flashed the red light. So pretty sure it's the CPU but will try the new CPU in the old mobo to find out for sure. EDIT** Tried the new CPU in the old board and still no go. Whatever happened with the PSU may have screwed the CPU as well (?)
  • Straight_ManStraight_Man Geeky, in my own way Naples, FL Icrontian
    Yes, possible.
  • Cliff_ForsterCliff_Forster Icrontian
    If you dropped the identical CPU into the new board and it didn't post, same behavior on the new power supply where the fan spins up full but nothing else, I'm still thinking failed CMOS on the mobo. What make and model is the machine out of curiosity?
  • Byron172Byron172 Adelaide, South Australia Member
    HP Compaq 7700dc (new PC) 7900dc (old PC)
  • Byron172Byron172 Adelaide, South Australia Member
    Unfortunately I can't test the power supply from model to model as the 7700dc has a slightly different PSU to the 7900 (has a 6 pin CPU power plug instead of the usual 4 pin).
  • Byron172Byron172 Adelaide, South Australia Member
    Cliff_Forster said:

    If you dropped the identical CPU into the new board and it didn't post, same behavior on the new power supply where the fan spins up full but nothing else, I'm still thinking failed CMOS on the mobo.

    I should clarify Cliff that the response from the new PC is slightly different in that it just beeps constant mobo alarm and the power LED flashes red light
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