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System can reboot but can't boot after shutdown

By BreL ·
I have just replaced a power supply (400W) after confirming the old one (450W) was faulty. After replacement, the system is able to run normally with many rounds of reboot but it just refuse to boot after shutdown gracefully. The symptom is there is no beep sound and no video signal although the power LED shows running at the casing. I can see the fans are spinning. Strange thing is the system is able to boot again on the next day or after some hours. The same problem comes back again after shutdown gracefully. May I know could this be due to insufficient power supply? What is the probable cause if there is no beep and w/o any video signal? Many thanks in advance.

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You replaced a 450W with a 400W ?...

by OldER Mycroft In reply to System can reboot but can ...

That would be my first concern.

Perhaps the 450W was under strain anyway, so replacing upward (500 - 550W) might have been a better idea.

Without knowing any details of your system and its hardware components, I really couldn't do any more than guess.

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Thanks Old Mycroft !

by BreL In reply to You replaced a 450W with ...

Basically it's just a simple P4 machine with one SATA disk, CD ROM & AGP card. Wonder what's the minimum acceptable power supply for a P4? As it can function properly (after some rest) except after shutdown, i hope there is a way to confirm the faulty part before buying one. Thanks.

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Faulty PSU's can cause all sorts of damage

by Jacky Howe In reply to System can reboot but can ...

and you really should have gone for the same wattage or above. Ageing motherboards tend to suffer the most, with either the onboard NIC or the AGP slot or it effecting the memory modules. <br>Check the memory.<br>
You can test the memory by running Windows Memory Diagnostic that can be downloaded from:
<br>
http://oca.microsoft.com/en/windiag.asp.
<br>
If memory problems are found, try re-seating the RAM. If it doesn't work, replace the defective RAM.
<br><br>
<i>Keep us informed as to your progress if you require further assistance.</i>
<br><br>
<i>If you think that any of the posts that have been made by all TR Members, have solved or contributed to solving the problem, please Mark them as <b>Helpful</b> so that others may benefit from the outcome.
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Thanks Jacky !

by BreL In reply to Faulty PSU's can cause al ...

I'll try to run the memory test. Anyway I've tried clearing the CMOS but that doesn't help. Will update the result once I've test the memory. Thank you.

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Updates on memory test

by BreL In reply to Thanks Jacky !

I could not run the memory test tool as there is no floppy drive in my system. I tried to test with one RAM at a time and the same problem still persist. So I doubt it's the RAM issue. Thanks.

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Maybe the PSU

by Jacky Howe In reply to Updates on memory test

isn't up to specs. To test this theory shutdown the PC and turn the power off from the outlet that is connected to the PSU and remove the cable from the PC. Plug it back in and turn on the power and see if you can restart the PC.
<br><br>
<i>Keep us informed as to your progress if you require further assistance.</i>
<br><br>
<i>If you think that any of the posts that have been made by all TR Members, have solved or contributed to solving the problem, please Mark them as <b>Helpful</b> so that others may benefit from the outcome.
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Thanks Jacky !

by BreL In reply to Maybe the PSU

Just tried it out and noticed this behaviour: I have to power off the wall socket after the proper shutdown in order to boot successfully. Without switching off the wall socket (after the graceful shutdown), the system will fail to boot. Any idea what cause this? Many thanks.

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Inferior PSU

by Jacky Howe In reply to Thanks Jacky !

that doesn't appear to be switching the power off to the board. Replace it with a swap and make up the difference if you can.
<br><br>
<i>Keep us informed as to your progress if you require further assistance.</i>
<br><br>
<i>If you think that any of the posts that have been made by all TR Members, have solved or contributed to solving the problem, please Mark them as <b>Helpful</b> so that others may benefit from the outcome.
</i>

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Don't forget HalfCut

by Jacky Howe In reply to Inferior PSU

he was the one that pointed it out first.

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Valid analysis !

by BreL In reply to Inferior PSU

Probably that makes some sense.... Many thanks for your advice, Jacky!

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