Computer needs warming up.

A friend has a computer that needs to be warmed up in cold weather
before it will start.

He blows hot air into it from a small electric floor-heater.

Then it starts OK.

What part in the computer needs fixing?

Peter Jason wrote:
A friend has a computer that needs to be warmed up in cold weather
before it will start.

How cold are we talking about here?


He blows hot air into it from a small electric floor-heater.

Then it starts OK.

What part in the computer needs fixing?


Bad caps? Cheap PS?

--
Take care,

Jonathan
-------------------
LITTLE WORKS STUDIO
http://www.LittleWorksStudio.com

On Mon, 24 Aug 2020 22:31:17 -0400, "Jonathan N. Little"
wrote:

Peter Jason wrote:
A friend has a computer that needs to be warmed up in cold weather
before it will start.

How cold are we talking about here?

It's about 10DegC The humidity is high too.


He blows hot air into it from a small electric floor-heater.

Then it starts OK.

What part in the computer needs fixing?


Bad caps? Cheap PS?

Peter Jason wrote:
A friend has a computer that needs to be warmed up in cold weather
before it will start.

He blows hot air into it from a small electric floor-heater.

Then it starts OK.

What part in the computer needs fixing?

Cold shrinks, heat expands.
It could be anything.
printed circuits, loose components,
what Jonathan said, caps, IC's, CPU, Power supply,
loose connector, plug, wire,
Test by selectively heating small areas then narrow it down to even
smaller areas, etc.

Jonathan N. Little wrote:
Peter Jason wrote:
A friend has a computer that needs to be warmed up in cold weather
before it will start.

How cold are we talking about here?

He blows hot air into it from a small electric floor-heater.

Then it starts OK.

What part in the computer needs fixing?


Bad caps? Cheap PS?


There have been reports of this kind of fallout before.

The motherboards are probably never verified in
a temperature chamber.

A suspect part of the motherboard, is the backfeed cutoff
logic. This is some ad-hoc design, where the designer
leaves their trademark on the board. For example, if
you received an Intel sample schematic, you would not adopt
their cutoff logic. You'd make your own. The cutoff
logic consists of a hodge podge of diodes, bipolar
transistors and MOSFETs arranged in such a way that when
a computer enters shutdown, currents don't flow into
the wrong parts and prevent the "sequencing" that's supposed
to happen at startup.

Some motherboards can't generate a RESET properly, because
of problems with that part of the design.

One motherboard, phantom current used to flow from
the computer monitor, back into the computer, and the
board would not RESET. If the monitor cable was disconnected,
the computer would promptly start - then plug the
monitor cable in and it's fine. Of course, the owner
hates the idea of doing this forever...

And if you allow a PC to get too cold, the weakest
link is the hard drive. You don't particularly want
to hit the "dew point" for the drive. Or cause frost to
form inside. If a hard drive does get that cold, it's
a good idea to let it equilibrate with normal room
temp for 24 hours, just in case. You're not supposed
to power it up immediately if it's full of frost.

Paul

On Mon, 24 Aug 2020 23:50:49 -0400, Paul
wrote:

Jonathan N. Little wrote:
Peter Jason wrote:
A friend has a computer that needs to be warmed up in cold weather
before it will start.

How cold are we talking about here?

He blows hot air into it from a small electric floor-heater.

Then it starts OK.

What part in the computer needs fixing?


Bad caps? Cheap PS?


There have been reports of this kind of fallout before.

The motherboards are probably never verified in
a temperature chamber.

A suspect part of the motherboard, is the backfeed cutoff
logic. This is some ad-hoc design, where the designer
leaves their trademark on the board. For example, if
you received an Intel sample schematic, you would not adopt
their cutoff logic. You'd make your own. The cutoff
logic consists of a hodge podge of diodes, bipolar
transistors and MOSFETs arranged in such a way that when
a computer enters shutdown, currents don't flow into
the wrong parts and prevent the "sequencing" that's supposed
to happen at startup.

Some motherboards can't generate a RESET properly, because
of problems with that part of the design.

One motherboard, phantom current used to flow from
the computer monitor, back into the computer, and the
board would not RESET. If the monitor cable was disconnected,
the computer would promptly start - then plug the
monitor cable in and it's fine. Of course, the owner
hates the idea of doing this forever...

And if you allow a PC to get too cold, the weakest
link is the hard drive. You don't particularly want
to hit the "dew point" for the drive. Or cause frost to
form inside. If a hard drive does get that cold, it's
a good idea to let it equilibrate with normal room
temp for 24 hours, just in case. You're not supposed
to power it up immediately if it's full of frost.

Paul

Thanks to all. It's probably the humidity which has been bad this
year. Does a computer generate heat when in sleep mode?

Try rubbing your penis vigorously on
the video card until your sperm comes out,
then try starting the computer.

(Note: This only works for Nvidia cards)

Peter Jason wrote:


Thanks to all. It's probably the humidity which has been bad this
year. Does a computer generate heat when in sleep mode?

A tiny amount.

The +5VSB regulator makes heat, and does so without
the fan running to remove it. The heat is contained
inside the PSU, and would be a poor means to keep the
entire chassis warm. The chassis will end up pretty
well as cold as the room it is in.

In the diagram here, it's the "Second Supply" in the
lower left corner. There's a switcher using Q12 that
makes a raw supervisory voltage (powers the TL494),
and a 78L05 linear regulator makes +5VSB. If a computer
was sleeping (S3), the power for the DIMMs is derived
from +5VSB. The "Second Supply" always runs, unless the
switch is off at the back, or the line cord is unplugged.

http://www.pavouk.org/hw/en_atxps.html

Modern supplies would be slightly more sophisticated
than that, and the 78L05 would be replaced by a switching
implementation instead. And that's because a modern supply
makes +5VSB @ 2.5A or +5VSB @ 3.0A. My Test Machine uses
1.5A of the +5VSB while it sleeps (S3) - a machine with DDR4 should
be a bit more economical than that. I would have to watch
it, if trying to charge an Apple device, using the left-over
power. Perhaps set it up for slow charging.

My Test Machine uses 1.7W if the computer is doing absolutely
nothing. If you plug in a USB stick, it draws power from +5VSB,
and that's registered as a slight additional (vampire) loading.

I can see these things, because the Test Machine is monitored
by a Kill-O-Watt meter.

Paul

Paul in Houston TX wrote:
Peter Jason wrote:
A friend has a computer that needs to be warmed up in cold weather
before it will start.

He blows hot air into it from a small electric floor-heater.

Then it starts OK.

What part in the computer needs fixing?

Cold shrinks, heat expands.
It could be anything.
printed circuits, loose components,
what Jonathan said, caps, IC's, CPU, Power supply,
loose connector, plug, wire,
Test by selectively heating small areas then narrow it down to even
smaller areas, etc.

There's a couple kinds of "won't start".

1) Fans not spinning when you push the button.

PSU always makes +5VSB. If you overload it, by
charging your Apple iPad, the +5VSB could go off.
If there is no +5VSB, there is no way for the front
mounted power switch to command the system to start.

2) Fans twitch when you push the power button.

This is a sign the PSU has tripped out on overload.
But normally, it won't recover until AC is removed
and restored again. A weak power supply will do this.
Normally, the situation only resolves when the PSU is
replaced (heat would not normally make it work again).
I have one supply here, that is "weak" like that.
It can run one PC fan from the +12V, but that's all the
current it can make. Maybe a quarter of an amp.

3) Fans run. Main rails come up. But, PC won't POST.

This can be caused by either PSU or motherboard
wired-OR Power_Good not indicating Power is Good.

"Back-feed cut" mis-behavior can be tied into this one.

These various causes, prevent escaping from RESET state.
A PC isn't allowed to run, unless all Power_Good circuits
agree that their power is good (includes motherboard
regulators).

If a "Back-feed cut" doesn't work right, the part of
the circuit that detects loss of power and prepares for
the presentation of power again, doesn't cycle properly.
It still thinks the power was on the whole time. You would
need a schematic to trace one of those down.

And that circuitry is like a Rube Goldberg machine.

Paul

On 2020-08-24 18:47, Peter Jason wrote:
A friend has a computer that needs to be warmed up in cold weather
before it will start.

He blows hot air into it from a small electric floor-heater.

Then it starts OK.

What part in the computer needs fixing?


Well, if you want to be fancy, put a volt meter
on your motherboard power supply connector's
"PWR-OK" pin and see if it switches immediately
when you power up or it waits a while and switches
when your computer starts to boot.

"https://www.smpspowersupply.com/connectors-pinouts.html

If it waits a while, replace the power supply.

On 8/24/2020 9:47 PM, Peter Jason wrote:
A friend has a computer that needs to be warmed up in cold weather
before it will start.

He blows hot air into it from a small electric floor-heater.

Then it starts OK.

What part in the computer needs fixing?



After reading the responses (so far) I did not see the
simplest solution to this challenge.

Don't turn it off!!

Have a better day all......................

Les

On Tue, 25 Aug 2020 07:43:22 -0400, ABLE1
wrote:

On 8/24/2020 9:47 PM, Peter Jason wrote:
A friend has a computer that needs to be warmed up in cold weather
before it will start.

He blows hot air into it from a small electric floor-heater.

Then it starts OK.

What part in the computer needs fixing?



After reading the responses (so far) I did not see the
simplest solution to this challenge.

Don't turn it off!!

Have a better day all......................

Les

He seems to happy with the floor heater. His computer is very old
anyway.

On 25/08/2020 05.50, Paul wrote:
Jonathan N. Little wrote:
Peter Jason wrote:
A friend has a computer that needs to be warmed up in cold weather
before it will start.

How cold are we talking about here?

He blows hot air into it from a small electric floor-heater.

Then it starts OK.

What part in the computer needs fixing?


Bad caps? Cheap PS?


There have been reports of this kind of fallout before.

The motherboards are probably never verified in
a temperature chamber.

I have a computer that needs warming up to boot, and it is not broken.


The thing is, its 30 MB hard disk uses a step motor to position the head
on each track. In winter, the positions are slightly off compared to
when it is warm, so there are read errors and fails to boot, till a few
minutes later when the hard disk warms up.

:-DDD

It runs with an 8086 at 8Mhz. Well, /runs/... you know :-D

--
Cheers, Carlos.

You need something that can read hypertext in my posts!! Clearly you won't know this so simply move on and do something else.


With over 1.2 billion devices now running Windows 10, customer
satisfaction is higher than any previous version of windows.

On Wed, 26 Aug 2020 05:20:51 +0100, ? Good Guy ?
wrote:


You need something that can read hypertext in my posts!! Clearly you won't know this so simply move on and do something else.


With over 1.2 billion devices now running Windows 10, customer
satisfaction is higher than any previous version of windows.

I've never heard of "hypertext"; what is it and why do I need it?