My Dimension 8400 screen suddenly went blank and the system rebooted. On
the reboot the system emitted several beeps (unfortunately I didn't record
the sequence). I turned the computer off by pressing the power button.
After several seconds I pushed the power button again. The system again
beeped several times, and the system fan started to spin very fast and very
(scary) loud. I immediately pushed the power button to shut it down.
Sometime later, I pulled the machine out from under the desk with the
intention of reproducing the problem and recording the beep sequence and the
diagnostic LEDs. To my surprise, the machine booted normally. The system
setup (BIOS) event log showed no errors, nor did the Windows error log.
However, I did notice that the power supply fan was not spinning. Should
the power supply fan on a Dimension 8400 spin all the time? Or does it only
spin when required?
My assumption is that the power supply fan failed, which led to a thermal
related shutdown. Would you agree? If so, can power supply fans be
(safely) replaced? Or should I just get a new power supply?
Scott Davis wrote:
> My Dimension 8400 screen suddenly went blank and the system rebooted. On
> the reboot the system emitted several beeps (unfortunately I didn't record
> the sequence). I turned the computer off by pressing the power button.
> After several seconds I pushed the power button again. The system again
> beeped several times, and the system fan started to spin very fast and very
> (scary) loud. I immediately pushed the power button to shut it down.
>
>
>
> Sometime later, I pulled the machine out from under the desk with the
> intention of reproducing the problem and recording the beep sequence and the
> diagnostic LEDs. To my surprise, the machine booted normally. The system
> setup (BIOS) event log showed no errors, nor did the Windows error log.
> However, I did notice that the power supply fan was not spinning. Should
> the power supply fan on a Dimension 8400 spin all the time? Or does it only
> spin when required?
>
>
>
> My assumption is that the power supply fan failed, which led to a thermal
> related shutdown. Would you agree? If so, can power supply fans be
> (safely) replaced? Or should I just get a new power supply?
>
>
>
> Thanks for you advice,
>
> Scott
>
>
Scott,
A thermal shutdown due to power supply fan failure is certainly a
possible explanation. The fan in the power supply does not spin all the
time, but it does spin most of the time. If the fan is not spinning at
all, a replacement power supply is in order.
Is there a lot of accumulated dust and dirt inside the system, inside
the power supply, on the processor heat sink, and on the processor
cooling fan? If so, a good cleaning makes sense.
One more thing: Keeping a computer on the floor under a desk does not
guarantee enough air to circulate and ventilate the computer... Ben Myers
Scott Davis wrote:
>> My Dimension 8400 screen suddenly went blank and the system
>> rebooted. On the reboot the system emitted several beeps
>> (unfortunately I didn't record the sequence). I turned the computer
>> off by pressing the power button. After several seconds I pushed the
>> power button again. The system again beeped several times, and the
>> system fan started to spin very fast and very (scary) loud. I
>> immediately pushed the power button to shut it down.
>>
>>
>>
>> Sometime later, I pulled the machine out from under the desk with the
>> intention of reproducing the problem and recording the beep sequence
>> and the diagnostic LEDs. To my surprise, the machine booted
>> normally. The system setup (BIOS) event log showed no errors, nor
>> did the Windows error log. However, I did notice that the power
>> supply fan was not spinning. Should the power supply fan on a
>> Dimension 8400 spin all the time? Or does it only spin when
>> required?
>>
>>
>>
>> My assumption is that the power supply fan failed, which led to a
>> thermal related shutdown. Would you agree? If so, can power supply
>> fans be (safely) replaced? Or should I just get a new power supply?
>>
>>
>>
>> Thanks for you advice,
>>
>> Scott
FWIW if you're comfortable with a soldering iron and working around possible
stored voltage the fan is easy to replace.
I just did one in an 8400. The leads are soldered in. (as opposed to
plugged) I took the PSU out (one screw), removed the fan (four screws),
clipped the wires (2) mid lead, soldered in a spare fan I had in the junk
box, taped and shrink wrapped the connections, reversed the disassembly and
was good to go.
Again the PSU has the potential for storing a nasty shock even while
unplugged so, caveat emptor, or whatever is Latin for repairer...
Replacing the whole PSU is easier and safer but replacing the fan (old one
was noisy and binding) was a lot cheaper, especially since I already had the
part.
> The fan in the power supply does not spin all the time, but it does
> spin most of the time.
I've never seen a Dim8400 PSU fan shut off whenever the computer was
on.
The Dim8400 has a fairly serious power supply inside it, as a relay
inside clicks when you turn it on or off. (Something I've only ever
seen on 470 watt and greater rated supplies.) I'd be very, very
surprised if that fan ever stopped.
Having had my Dim8300 PSU apart once (it's a Lite-On made unit if
anyone cares), I can say that some Dell power supplies do have a
thermal fan control in place. However, it cannot ever shut the fan
completely off.
> One more thing: Keeping a computer on the floor under a desk
> does not guarantee enough air to circulate and ventilate the
> computer... Ben Myers
Under a desk is usually good enough, as long as the machine is in free
air. Cooler air tends to sink after all. It's the systems that I find
in closed under-desk cabinets that are thrilling. I love opening a
door on someone's computer desk and feeling a large wave of heat come
out.
The better systems have wound their fans up in some kind of an effort
to stay cool. Cheap ones usually cook after so many times.
"Doug" <datapod@yahoo.com> wrote in message
news:h3ql1m$9gi$1@news.eternal-september.org...
>
> Scott Davis wrote:
>>> My Dimension 8400 screen suddenly went blank and the system
>>> rebooted. On the reboot the system emitted several beeps
>>> (unfortunately I didn't record the sequence). I turned the computer
>>> off by pressing the power button. After several seconds I pushed the
>>> power button again. The system again beeped several times, and the
>>> system fan started to spin very fast and very (scary) loud. I
>>> immediately pushed the power button to shut it down.
>>>
>>>
>>>
>>> Sometime later, I pulled the machine out from under the desk with the
>>> intention of reproducing the problem and recording the beep sequence
>>> and the diagnostic LEDs. To my surprise, the machine booted
>>> normally. The system setup (BIOS) event log showed no errors, nor
>>> did the Windows error log. However, I did notice that the power
>>> supply fan was not spinning. Should the power supply fan on a
>>> Dimension 8400 spin all the time? Or does it only spin when
>>> required?
>>>
>>>
>>>
>>> My assumption is that the power supply fan failed, which led to a
>>> thermal related shutdown. Would you agree? If so, can power supply
>>> fans be (safely) replaced? Or should I just get a new power supply?
>>>
>>>
>>>
>>> Thanks for you advice,
>>>
>>> Scott
>
> FWIW if you're comfortable with a soldering iron and working around
> possible
> stored voltage the fan is easy to replace.
>
> I just did one in an 8400. The leads are soldered in. (as opposed to
> plugged) I took the PSU out (one screw), removed the fan (four screws),
> clipped the wires (2) mid lead, soldered in a spare fan I had in the junk
> box, taped and shrink wrapped the connections, reversed the disassembly
> and
> was good to go.
>
> Again the PSU has the potential for storing a nasty shock even while
> unplugged so, caveat emptor, or whatever is Latin for repairer...
>
> Replacing the whole PSU is easier and safer but replacing the fan (old one
> was noisy and binding) was a lot cheaper, especially since I already had
> the
> part.
>
> D
>
>
Thank you Ben, William, and Doug for the helpful feedback
I was able to reproduce the failure. The diagnostice LEDs indicated a
memory error. By systematically swapping out the paired memory modules I
was able to isolate the bad DIMM. I've orderd new memory from Crucial, and
a new power supply because the fan was not spinning. And I followed Ben's
advice and cleaned the dust out of the case (there was a fair amount).
As a side note, Dell wanted to sell me refurbished power supply for $62.52
(including tax and shipping). I bought a new one (identical part#) from a
highly rated ebay seller for $25.00, including free priority shipping.
Dimension 8400 Problem 
Linear Mode
