Maybe PSU Problem?

[Terry Strachan]

Hi,

I have just built up a PC using P4 Dual Core Processor and a 512PCI-E
graphics 2gig Ram etc..
The case came with a 400 PSU, so I replaced that with a 550.

When I fire up the PC - all fans and lights come on but the screen doesn't
flicker into life
(screen power light stays orange)

However, If I switch Off and straight back on - it fires up ok and
everything works fine.
(used for several hours without hiccup)

I think its probably a capacitor in the PSU discharging - I just wondered if
anyone else has had a similar experience, and what turned out to be there
problem.

Many thanks

Terry.

 

[Mike T.]

Hi,

I have just built up a PC using P4 Dual Core Processor and a 512PCI-E
graphics 2gig Ram etc..
The case came with a 400 PSU, so I replaced that with a 550.

When I fire up the PC - all fans and lights come on but the screen doesn't
flicker into life
(screen power light stays orange)

However, If I switch Off and straight back on - it fires up ok and
everything works fine.
(used for several hours without hiccup)

I think its probably a capacitor in the PSU discharging - I just wondered
if
anyone else has had a similar experience, and what turned out to be there
problem.

Many thanks

Terry.

Not enough information. When you say switch Off and straight back on, how,
EXACTLY, are you doing that? -Dave

 

[Terry Strachan]

Not enough information. When you say switch Off and straight back on, how,
EXACTLY, are you doing that? -Dave

Sorry, never thought about that bit.

Whilst all fans are spinning and the system is not booting (or at least no
monitor display)
Hold the Power button (approx 5sec) till the system switches off. Then hit
the power button again, straight away.

Terry.

 

[Ed Medlin]

Hi,

I have just built up a PC using P4 Dual Core Processor and a 512PCI-E
graphics 2gig Ram etc..
The case came with a 400 PSU, so I replaced that with a 550.

When I fire up the PC - all fans and lights come on but the screen doesn't
flicker into life
(screen power light stays orange)

However, If I switch Off and straight back on - it fires up ok and
everything works fine.
(used for several hours without hiccup)

I think its probably a capacitor in the PSU discharging - I just wondered
if
anyone else has had a similar experience, and what turned out to be there
problem.

Many thanks

Terry.

That problem is classic for a PSU problem, but not only a PSU problem. Since
you have that new 400w you took out I would try that first.

Ed

 

[Mike T.]

Sorry, never thought about that bit.

Whilst all fans are spinning and the system is not booting (or at least no
monitor display)
Hold the Power button (approx 5sec) till the system switches off. Then
hit
the power button again, straight away.

Terry.

Sounds like a bad power supply. When you turn on an ATX system, there is a
delay before anything happens. During this, DC voltages are ramping up to
(hopefully) within design specifications. When that happens, the power
supply will send a power_OK signal to mainboard. The CPU will not do
ANYTHING until it gets that power_OK signal from the mainboard (that
originated in the power supply). What your specific system is experiencing
sounds like some kind of safety time-out circuit kicking in. That is, turn
power on, timer starts ticking, if power_OK line is not hot within some
number of milliseconds, no boot.

The reason shutting down and restarting (quickly) works is likely due to
capacitors (which work somewhat like batteries, but are used to regulate DC
voltages). That is, after being shut off a while, capacitors drain and then
they take a while to charge up again. But if you turn off and back on
quickly enough, capacitors are still mostly charged, so they don't take as
long to charge up again. So my theory is, if you start with the caps
charged, the power_OK is sent before the system times out and refuses to
boot.

I'd be shocked if replacing the power supply didn't fix this problem. -Dave