Weird power readings and boot failure

[tpuk57]

Seasons Greetings

Have a real strange one

PC intermitently won't boot at all when it does get message boot disc failure insert system disc.

Have tried swapping a known good HDD but get same message. Also took voltage readings and both 12 and 5v rails are reading twice what they should (24/25v and 10.6v).

Swapped known good psu and still getting same readings.

Any help greatly appreciated.

Thanks in advance

[Steve R Jones]

The disk controller could have died.
Ribbon cable to the drive could be faulty.

[tpuk57]

Is it possible to replace the disk controller?

Will also try replacing the ribboncable, just really thrown by the double voltage readings

[Steve R Jones]

The controller is built into the mainboard...You can get a PCI controller for not too much money...

[SuperSparks]

What are you taking those volatage reading with? If those were real voltages then your PC would have died (quite spectacularly probably)

[tpuk57]

Thats what I can't figure out - am using a volt meter and reading from a connecter and mob. Even with a good psu taken from a working pc it throws these weird readings. Thought at first the psu had gone as pc wouldn't boot. but even when pc booting up it shows these readings but returns message boot disc failure insert system disc
Is there a valid way to test psu without it being connected to mob.

[dneilson]

At this point I'd really suspect that meter you're using. Do you have another meter you could use? Do you have any other known voltages (other than the computer PS) that you could check it against?

[SuperSparks]

Is there a valid way to test psu without it being connected to mob.

Yes indeed, here's how:

Testing PSU voltages