Please help with dead system

[Chris]

I have a pc AMD 2000+ (home built) that will not power on. It powers
on but no post, no beep codes just cpu fan, power supply fan and hard
disk comes on. I believe it;s the CPU because when the problem
happeed there was alot of dust across the top of the heat-sink
completely covering the top restricting flow of air to the heat-sink.
Since there are no beeps, no post, no video and the dirty heat sink,
I'm guessing the cpu. Can anyone offer any advice? I don't want to
waste money replacing the cpu and I have no known good cpu's or
motherboards for this cpu.

Chris
If life seems jolly rotten
There's spmething you've forgotten
and thats to laugh and smile and dance and sing!

 

[KC Computers]

I have a pc AMD 2000+ (home built) that will not power on. It powers

on but no post, no beep codes just cpu fan, power supply fan and hard
disk comes on. I believe it;s the CPU because when the problem
happeed there was alot of dust across the top of the heat-sink
completely covering the top restricting flow of air to the heat-sink.
Since there are no beeps, no post, no video and the dirty heat sink,
I'm guessing the cpu. Can anyone offer any advice? I don't want to
waste money replacing the cpu and I have no known good cpu's or
motherboards for this cpu.

It's pretty rare for a CPU to fail like that. It's more likely a
motherboard
or power supply issue. Can you borrow a power supply to try?

 

[Tony Hill]

I have a pc AMD 2000+ (home built) that will not power on. It powers
on but no post, no beep codes just cpu fan, power supply fan and hard
disk comes on. I believe it;s the CPU because when the problem
happeed there was alot of dust across the top of the heat-sink
completely covering the top restricting flow of air to the heat-sink.
Since there are no beeps, no post, no video and the dirty heat sink,
I'm guessing the cpu. Can anyone offer any advice? I don't want to
waste money replacing the cpu and I have no known good cpu's or
motherboards for this cpu.

Standard process here is to try to isolate the issue. The problem
sounds like you have an electrical short somewhere in your system,
which means it could be ANY component.

First, pull out ALL unnecessary components, ie any PCI cards, anything
connected to USB, keyboard, mouse, external speakers, hard drives,
floppy, etc. etc. Basically you want to be left with nothing other
than your motherboard, CPU and power supply. At the very least this
should give you some beep complaining about the lack of memory.

If you get nothing at that point, then at least you've narrowed it
down to three parts, CPU, power supply and motherboard. Now, at this
point there are only two options. First is to physically inspect the
parts to see if there is an obvious proble. Most important here is to
check the capacitors on the motherboard to see if they are bulging,
leaking or just otherwise looking ugly. Given the approximate age of
your system, I would give it about a 75% or higher probability that
this is where you problem is.

Now, if a visual inspection doesn't bring up anything obvious, the
second option is to swap parts. Of course, this requires compatible
replacement parts in order to test things, so hopefully you've got a
similar spare PC lying about and/or have a friend that does. Swap
parts out one at a time to try to isolate the issue, then replace the
defective part.

 

[Arno Wagner]

I have a pc AMD 2000+ (home built) that will not power on. It powers
on but no post, no beep codes just cpu fan, power supply fan and hard
disk comes on. I believe it;s the CPU because when the problem
happeed there was alot of dust across the top of the heat-sink
completely covering the top restricting flow of air to the heat-sink.
Since there are no beeps, no post, no video and the dirty heat sink,
I'm guessing the cpu. Can anyone offer any advice? I don't want to
waste money replacing the cpu and I have no known good cpu's or
motherboards for this cpu.

If the HDD starts, then both +5V and +12V from the PSU is
reasonably good. HDDs have bad power detectors so they can
decide when to spin-up and spin-down.

One way you could get your symptoms is if the reset line
(called power-good) from the PSU is failing. HDDs atsrt on
their own. The way to test for this is with a different
PSU.

If the CPU is broken, you should get the according
beep code (or POST code, if your mainboard has a POST display).
However if it is partially broken, that may not work....

One thing you may try is removing the CPU and see whether you
get beep codes. If you do not, then the mainboard is likely
broken. This does not matter a lot, since you cannot get
CPUs or mainboards from that generation anymore anyways.

But first, remove everything, except CPU, RAM and video card.
See wheter it still does not start. Then test with a different
PSU. Then you can try the CPU removal experiment.

Arno

 

[George Macdonald]

I have a pc AMD 2000+ (home built) that will not power on. It powers
on but no post, no beep codes just cpu fan, power supply fan and hard
disk comes on. I believe it;s the CPU because when the problem
happeed there was alot of dust across the top of the heat-sink
completely covering the top restricting flow of air to the heat-sink.
Since there are no beeps, no post, no video and the dirty heat sink,
I'm guessing the cpu. Can anyone offer any advice? I don't want to
waste money replacing the cpu and I have no known good cpu's or
motherboards for this cpu.

Sounds about the right time frame for the capacitor problem - check the
capacitors, especially the cluster near the CPU, for doming of the top and
leakage around the base. See www.badcaps.com for examples.

 

[nobody]

Standard process here is to try to isolate the issue. The problem
sounds like you have an electrical short somewhere in your system,
which means it could be ANY component.

First, pull out ALL unnecessary components, ie any PCI cards, anything
connected to USB, keyboard, mouse, external speakers, hard drives,
floppy, etc. etc. Basically you want to be left with nothing other
than your motherboard, CPU and power supply. At the very least this
should give you some beep complaining about the lack of memory.

If you get nothing at that point, then at least you've narrowed it
down to three parts, CPU, power supply and motherboard. Now, at this
point there are only two options. First is to physically inspect the
parts to see if there is an obvious proble. Most important here is to
check the capacitors on the motherboard to see if they are bulging,
leaking or just otherwise looking ugly. Given the approximate age of
your system, I would give it about a 75% or higher probability that
this is where you problem is.

Now, if a visual inspection doesn't bring up anything obvious, the
second option is to swap parts. Of course, this requires compatible
replacement parts in order to test things, so hopefully you've got a
similar spare PC lying about and/or have a friend that does. Swap
parts out one at a time to try to isolate the issue, then replace the
defective part.

Smell the power supply. If it smells like something is burned,
probably it is.

NNN

 

[Franc Zabkar]

If the HDD starts, then both +5V and +12V from the PSU is
reasonably good. HDDs have bad power detectors so they can
decide when to spin-up and spin-down.

One way you could get your symptoms is if the reset line
(called power-good) from the PSU is failing. HDDs atsrt on
their own. The way to test for this is with a different
PSU.

If the CPU is broken, you should get the according
beep code (or POST code, if your mainboard has a POST display).
However if it is partially broken, that may not work....

One thing you may try is removing the CPU and see whether you
get beep codes. If you do not, then the mainboard is likely
broken.

If the CPU is not present or is not working, then you will not get any
beep codes.

- Franc Zabkar

 

[Franc Zabkar]

Standard process here is to try to isolate the issue. The problem
sounds like you have an electrical short somewhere in your system,

A short would shut down the PSU. Clearly this is not happening in the
OP's case.

- Franc Zabkar

 

[Arno Wagner]

On 16 Nov 2006 00:36:03 GMT, Arno Wagner <[email protected]> put finger
to keyboard and composed:

If the CPU is not present or is not working, then you will not get any
beep codes.

That is wrong. The beep codes are produced by the keyboard
MCU and that will beep a "CPU not present" if it is not
contacted by the CPU after a certain time.

Arno

 

[Chris]

That is wrong. The beep codes are produced by the keyboard
MCU and that will beep a "CPU not present" if it is not
contacted by the CPU after a certain time.

Arno

Thanks for the replies so far... I have swapped the power supply for a
known good supply, removed all cards, usb cables ram etc... Still no
change. No beep codes and the CPU (heat sink) does not get warm at
all. I gave it a good visual inspection under a magnifying glass (I
am a pc technician) and there does not appear to be any problem with
the motherboard. CPU's are still available for this system, but I'm
not sure about MB's except maybe used... I have a post card but it's
ISA and the MB doesn't have any ISA slots. I can try to boot the
system with no cpu and see what happens. It's been very rare in my
experience for a cpu to go bad, in over 10 years I've only seen one
and it was a bad cache on a g3 chip, but at work I've always had known
good equipment and with this I don't and I am not working at the
moment. Any other ideas?

Chris
If life seems jolly rotten
There's spmething you've forgotten
and thats to laugh and smile and dance and sing!

 

[Tony Hill]

A short would shut down the PSU. Clearly this is not happening in the
OP's case.

In my experience a short will shut down the PSU only about 50% of the
time at most. Other times it just hangs in a state exactly like the
original poster described, no POST, no video, no beeps, but everything
seems to be getting power fine.

A short will only shut down the PSU if the voltage can be directly
pulled from that power supply. If the short is on the far side of a
voltage regulator which has a maximum current that it will supply,
then your PSU never sees the short circuit and just happily goes about
it's business. Another possibility is that the short circuit only
lasted about a milisecond until it burned out some other chip and
caused an open circuit. Same basic symptoms and same fix either way.

 

[Tony Hill]

If the CPU is not present or is not working, then you will not get any
beep codes.

That depends entirely on the system and how the CPU failed. Some
systems will beep if they do not detect a CPU, others will not. Of
those that will beep if a CPU is not detected, they *might* beep if
the CPU has failed or they might not. Beep codes are (usually)
handled entirely by the motherboard with no CPU intervention.

 

[Arno Wagner]

That is wrong. The beep codes are produced by the keyboard
MCU and that will beep a "CPU not present" if it is not
contacted by the CPU after a certain time.

Arno

[/QUOTE]

Thanks for the replies so far... I have swapped the power supply for a
known good supply, removed all cards, usb cables ram etc... Still no
change. No beep codes and the CPU (heat sink) does not get warm at
all. I gave it a good visual inspection under a magnifying glass (I
am a pc technician) and there does not appear to be any problem with
the motherboard. CPU's are still available for this system, but I'm
not sure about MB's except maybe used... I have a post card but it's
ISA and the MB doesn't have any ISA slots. I can try to boot the
system with no cpu and see what happens. It's been very rare in my
experience for a cpu to go bad,

I agree to that. Basically only the very visible "chip is burnt"
type, when the heatsink falls off an older CPU.

in over 10 years I've only seen one
and it was a bad cache on a g3 chip, but at work I've always had known
good equipment and with this I don't and I am not working at the
moment. Any other ideas?

Well, the total no-reaction would lead me to believe that the
chipset is shot. With no CPU you should get a beep-code.
If not, the board is broken.

Arno

 

[Franc Zabkar]

That depends entirely on the system and how the CPU failed. Some
systems will beep if they do not detect a CPU, others will not. Of
those that will beep if a CPU is not detected, they *might* beep if
the CPU has failed or they might not. Beep codes are (usually)
handled entirely by the motherboard with no CPU intervention.

Just to be clear, you don't mean *all* the POST beep codes, do you?

- Franc Zabkar

 

[Franc Zabkar]

That is wrong. The beep codes are produced by the keyboard
MCU and that will beep a "CPU not present" if it is not
contacted by the CPU after a certain time.

Arno

I was thinking of BIOS/POST beep codes. These require a working CPU. I
was not aware that the keyboard MCU in a modern PC chipset could
actually control the speaker (it is normally accessed via I/O port
61h). In any case, a "POST display" requires that error code data be
sent to I/O port 80h. I can't see how the keyboard MCU could do this.

- Franc Zabkar

 

[Franc Zabkar]

In my experience a short will shut down the PSU only about 50% of the
time at most. Other times it just hangs in a state exactly like the
original poster described, no POST, no video, no beeps, but everything
seems to be getting power fine.

I've repaired thousands of power supplies in all manner of equipment.
I don't recall any case where a short on one of the rails of a PC SMPS
did not shut down the supply. In fact short circuit current protection
is a design requirement. However, I *have* seen plenty of cases in
other equipment where a particular rail has fused in response to a
short, or where the load has been switched off by a protection
circuit.

A short will only shut down the PSU if the voltage can be directly
pulled from that power supply. If the short is on the far side of a
voltage regulator which has a maximum current that it will supply,
then your PSU never sees the short circuit and just happily goes about
it's business.

Yes, that's possible, although I think such regulators are designed to
shut down, assuming they have not failed.

Another possibility is that the short circuit only
lasted about a milisecond until it burned out some other chip and
caused an open circuit. Same basic symptoms and same fix either way.

There is nothing in the OP's post that would have me automatically
suspecting a short.

- Franc Zabkar

 

[Trent]

That is wrong. The beep codes are produced by the keyboard
MCU and that will beep a "CPU not present" if it is not
contacted by the CPU after a certain time.

Proof please. The beep codes are generated from the 8254 timer chip, which
must be programmed by the processor. If the processor is missing or cannot
do code/data fetches from the BIOS ROM, there are *no* post codes. Period.

 

[The little lost angel]

Proof please. The beep codes are generated from the 8254 timer chip, which
must be programmed by the processor. If the processor is missing or cannot
do code/data fetches from the BIOS ROM, there are *no* post codes. Period.

I had seen modern motherboards which are able to tell if the CPU is
not working. Specifically on an older AOpen K7 board, I had the
occasion where the board was able to tell me "Your CPU may have a
problem" using the beeper as a voice speaker.

My older MSI Socket A board also had a diagnostic LED that had codes
for a improperly installed or non-functional CPU, basically equates to
a dead CPU.

My current one probably has beep codes for that as well but I'm too
lazy to dig up the manual pPp

 

[Arno Wagner]

id: <[email protected]>:

Proof please. The beep codes are generated from the 8254 timer chip, which
must be programmed by the processor. If the processor is missing or cannot
do code/data fetches from the BIOS ROM, there are *no* post codes. Period.

Since your information is wrong, I don't feel I have to proof
anything. But please remain unenlightened, if you want.

Otherwise have a look at the schematics again. Should be at least PC-AT,
since I think the original PC and XT actually could not do this AFAIK.

Arno

 

[Franc Zabkar]

I had seen modern motherboards which are able to tell if the CPU is
not working. Specifically on an older AOpen K7 board, I had the
occasion where the board was able to tell me "Your CPU may have a
problem" using the beeper as a voice speaker.

If the speaker was talking to you, then clearly the code that does
this is being executed by some kind of CPU. I'd be very surprised if
such intelligence was incorporated into the chipset. Perhaps your CPU
was only partially bad.

My older MSI Socket A board also had a diagnostic LED that had codes
for a improperly installed or non-functional CPU, basically equates to
a dead CPU.

If it's just a single LED, then that's a lot easier than generating a
beep code.

My current one probably has beep codes for that as well but I'm too
lazy to dig up the manual pPp

All BIOSes appear to have beep codes for malfunctioning CPUs. However,
AFAICS, these require that the CPU has enough functionality to execute
BIOS code. A totally dead CPU cannot execute anything.

Having said the above, I *could* envisage a scenario where a spare pin
on the keyboard MCU could be used to drive the speaker by ORing it
with the normal data path. Such a design *could* detect an empty CPU
socket, but none of your anecdotes confirm that this is what was
happening in your case.

- Franc Zabkar