If the power supply is okay but no bios loading

[mark35]

CPU tests ok, green light on motherboard, power supply on and off switch is the only power control, start button does nothing, not even if you hold it in for a while. There is proper voltage to all drives, but none seem to operate. Neither cd drive will open and no display is shown on the monitor. I've looked thoroughly for any motherboard dark spots or circuit board cracks and have found none. I have tried booting from the floppy drive, but it doesn't seem to be operating either. I removed the battery and tried to reset the bios but that also didn't work. What should my next step be? The unit is an hp a520n. Oh, I also get no beeps if I remove the memory. Thanks

 

[GhislainG]

If the CPU and the PSU are fine, then the motherboard probably has died. How did you test the CPU and the PSU?

 

[mark35]

I was able to use the psu on another system and it operated fine. The CPU was not tested, because I'm not sure how to do that.

 

[GhislainG]

If the PSU is known good, then you should disconnect everything that's not required from the motherboard (hard disk, floppy, etc. Then try to power up. If that doesn't work, then you could have your CPU tested by a shop if it isn't too expensive. If the CPU is good, a replacement motherboard is required, but it's expensive. You could get it fixed for less, but is it worth it for a 5 year old computer?

 

[jsc]

Well, if you disconnect everything except the CPU and PSU (no drives, video card, or memory) from the motherboard and try to boot, you should hear a series of long, single beeps indicating no memory. If you hear silence; the PSU, motherboard, or CPU is bad. And if you have tested the PSU in another system, the motherboard is the next likely suspect.

 

[mark35]

Well, if you disconnect everything except the CPU and PSU (no drives, video card, or memory) from the motherboard and try to boot, you should hear a series of long, single beeps indicating no memory. If you hear silence; the PSU, motherboard, or CPU is bad. And if you have tested the PSU in another system, the motherboard is the next likely suspect.

I actually have removed all of the suggested items but I left the video cord connected to the monitor. No beeps at all! Is there a way to test the cpu., continuity, ohms, etc., to see where a problem might be? I'll have to get a diagram from HP if they have one that will give values of measurements between certain points. It might be fun to try. Thanks for the response. Things are getting clearer now!

 

[JackNaylorPE]

A lot of newer mobos have LED's instead of speakers. Check your MoBo manual for troubleshooting procedures.

 

[mark35]

A lot of newer mobos have LED's instead of speakers. Check your MoBo manual for troubleshooting procedures.

Thank you for trying to help me! I do not have documentation, as this is my daughters machine. I'm beginning to think that it is relating to the fact that the on/off button on the front of the computer is shorted somehow. It has no effect on whether the machine runs or not. As soon as I turn the power supply switch on it turns the fans on, including the cpu. No action whatsoever is seen on the monitor. The light at the top of the on/off switch goes on but does not blink or anything. I would love to have a schematic from hp showing some values on the board, but I just don't think it is worth it. Thanks again for your comment. By the way, if anyone else reads this message, I hate to decide between two good answers, just whose was the best. I think that everyone tries, using the knowledge they have gained and should all receive accolades for just trying to help. Thanks again