Desktop Keeps Turning On/Off

I have a desktop that just started turning itself on and off continuously.

Basically, when I push the power button, the PC turns on for approx. 1-2
seconds, then it turns off for approx. 1-2 seconds; and so on, and so on...

I've installed a brand new power supply after the PC started this
behavior, so that is not the problem.

I've used different power cords, and that is not the problem either.

I've checked all the cables and memory sticks inside the case.
Everything is properly set.

What could it be that makes the PC turn on and off constantly?

Is there some sort of diagnostic DVD that would help me out in
understanding where the problem is?

Thanks.
--
tb

tb wrote:
I have a desktop that just started turning itself on and off continuously.

Basically, when I push the power button, the PC turns on for approx. 1-2
seconds, then it turns off for approx. 1-2 seconds; and so on, and so on...

I've installed a brand new power supply after the PC started this
behavior, so that is not the problem.

I've used different power cords, and that is not the problem either.

I've checked all the cables and memory sticks inside the case.
Everything is properly set.

What could it be that makes the PC turn on and off constantly?

Is there some sort of diagnostic DVD that would help me out in
understanding where the problem is?

Thanks.

You're going to have to recollect "normal" behavior on the machine.

Some hardware designs, the BIOS code is designed to do a "double start".
The machine starts from cold the first time, the BIOS checks the
recorded hardware settings, and loads up an overclock controller chip
with the settings (FID and VID). Then, the BIOS pushes the RESET button
for itself, and the machine starts again. Somehow, the BIOS keeps track
that it is entering this code for the second time, and a "normal" boot
sequence then happens.

Now, I can't say for sure, where that status bit is recorded. It
could be stored in the high part of the CMOS table (256 bytes
of RAM in the Southbridge). If the CMOS battery was flat, it
really should not matter, since the +5VSB on the power supply keeps
everything powered. On the first start, if the CMOS (NVRAM) is
corrupt, the BIOS should restore defaults and carry on.

So the question is, how can we throw such a design into a loop ?

Does your machine normally do double-starts ? Not all machines do.

The machine I'm typing on, does double starts, but only
after the power has been entirely turned off. Most normal
starts, are single-start.

*******

If a machine switches off due to THERMTRIP, it should stay off.
THERMTRIP should latch, requiring the machine to be power
cycled, before it will attempt to start. THERMTRIP happens
when the CPU heatsink falls off, and the CPU overheats in the
first two seconds. THERMTRIP exists on both platforms, and
has been around since the Athlon chips were burning out.

Check that both the CPU fan is turning, and the clamps for the
heatsink are secure. If the heatsink is attached, but the rotor
on the fan jams, it should take longer (30 seconds maybe), before
the heatsink gets hot enough (100C+) for THERMTRIP to trip. When
the time constant is 2 seconds on a THERMTRIP, that means the
heatsink isn't touching the surface of the CPU any more.

Your symptoms don't sound like THERMTRIP. Still, the time constant
of 2 seconds is concerning. It's either the double-start BIOS
time constant, or it's THERMTRIP. It would require
a serious malfunction of those features, to loop like
you describe.

Paul

tb wrote:
I have a desktop that just started turning itself on and off continuously.

Basically, when I push the power button, the PC turns on for approx. 1-2
seconds, then it turns off for approx. 1-2 seconds; and so on, and so on...

I've installed a brand new power supply after the PC started this
behavior, so that is not the problem.

I've used different power cords, and that is not the problem either.

I've checked all the cables and memory sticks inside the case.
Everything is properly set.

What could it be that makes the PC turn on and off constantly?

Is there some sort of diagnostic DVD that would help me out in
understanding where the problem is?

Thanks.

Check your CMOS battery voltage. I have seen computers do that when the
battery is below an acceptable level.

On 4/30/2017 10:09 PM, tb wrote:
I have a desktop that just started turning itself on and off continuously.

Basically, when I push the power button, the PC turns on for approx. 1-2
seconds, then it turns off for approx. 1-2 seconds; and so on, and so on...

I've installed a brand new power supply after the PC started this behavior,
so that is not the problem.

I've used different power cords, and that is not the problem either.

I've checked all the cables and memory sticks inside the case. Everything
is properly set.

What could it be that makes the PC turn on and off constantly?

Is there some sort of diagnostic DVD that would help me out in
understanding where the problem is?

Thanks.

Is your BIOS set to automatically restart in the previous state when power
fails? That would be the first thing I'd disable for troubleshooting. The
last time I had anything like that going on I had a heatsink that had
completely fallen off the CPU (damned Intel plastic pins!) and it would
start and stop on its own but it took a lot longer to cycle than what you
describe.

On 4/30/2017 at 9:09:41 PM tb wrote:

I have a desktop that just started turning itself on and off
continuously.

Basically, when I push the power button, the PC turns on for approx.
1-2 seconds, then it turns off for approx. 1-2 seconds; and so on,
and so on...

I've installed a brand new power supply after the PC started this
behavior, so that is not the problem.

I've used different power cords, and that is not the problem either.

I've checked all the cables and memory sticks inside the case.
Everything is properly set.

What could it be that makes the PC turn on and off constantly?

Is there some sort of diagnostic DVD that would help me out in
understanding where the problem is?

Thanks.

Well, the culprit appears to be a bad DIMM socket. When there is no
system memory di Channel B, DIMM 1, the computer stops turning on/off
repeatedly.

--
tb

tb wrote:
On 4/30/2017 at 9:09:41 PM tb wrote:

I have a desktop that just started turning itself on and off
continuously.

Basically, when I push the power button, the PC turns on for approx.
1-2 seconds, then it turns off for approx. 1-2 seconds; and so on,
and so on...

I've installed a brand new power supply after the PC started this
behavior, so that is not the problem.

I've used different power cords, and that is not the problem either.

I've checked all the cables and memory sticks inside the case.
Everything is properly set.

What could it be that makes the PC turn on and off constantly?

Is there some sort of diagnostic DVD that would help me out in
understanding where the problem is?

Thanks.

Well, the culprit appears to be a bad DIMM socket. When there is no
system memory di Channel B, DIMM 1, the computer stops turning on/off
repeatedly.


The first version of Intel Management Engine, used a
fixed scheme for the microcontroller. One of the
DIMM slots is supposed to be populated first with
memory. The microcontroller in the chipset then
grabs a chunk.

Funny that it causes switch-off.

Normally, when a memory configuration setting is
not correct, the BIOS beeps the PC case speaker
with a beep pattern. So that eventually the
user will read the memory section in the manual
and spot the error.

There are some other installation pattern rules,
but they had to do with dual channel. And that
was on a couple generations of AMD Athlon64.

Paul