Pc broken

[John Rudd]

Fortunately I don't solely rely on it for internet...,,
I was trying to send an email to one board member this afternoon, when the pc just stopped as if it had been switched off but it rebooted....it did this four times before I gave up.....
It appears to do this randomly....

So before I start ripping into it, any suggestions for a likely cause?

[philf]

Fortunately I don't solely rely on it for internet...,,
I was trying to send an email to one board member this afternoon, when the pc just stopped as if it had been switched off but it rebooted....it did this four times before I gave up.....
It appears to do this randomly....

So before I start ripping into it, any suggestions for a likely cause?

John,

Is the CPU fan still running? A laptop I had kept doing the same and I found the fan had stopped working.

Good luck.

Phil.

[steampunkpete]

I had a laptop that did this, it turned out to be a dodgy battery connection.

Does it stay on long enough to run your antivirus?

Can you start it in safe mode? If so that might be a place to start with running the antivirus. You might also try malwarebytes free version just in case.

I'll ask my son when I see him later - he works in IT.

Good luck

Pete

[John Rudd]

The duration for uptime varies....not long enough IMHO to run any av sw.

I'll take the covers off tomorrow and have a shuftie inside, clean out the dust and reseat all the connectors boards memory etc...

[Pete.]

It does sound like a heat issue. A word of warning though - don't use your hoover to clean the motherboard or expansion cards because they can generate static in the tube and fry stuff like memory modules. Use a paint brush to brush the dust out, or an air line if you have a compressor, or failing that an air duster (just a can of air you can buy). Oh and do it outside

[John Swift]

Hi John

when you clean inside your PC have a look inside the power supply as well
you may find its full of fluff  and has been over heating for a while

look for scorched patches of PCB and discoloured / swollen capacitors (near the output wiring )

most of my PC faults have been due to a faulty hard drive or power supply

how long does it run for before it reboots ?
you could disconnect the hard drive(s) and boot from the operating system installation disk and see how long it runs

   John

[BaronJ]

Fortunately I don't solely rely on it for internet...,,
I was trying to send an email to one board member this afternoon, when the pc just stopped as if it had been switched off but it rebooted....it did this four times before I gave up.....
It appears to do this randomly....

So before I start ripping into it, any suggestions for a likely cause?

Hi John,
You haven't said whether it's a laptop or desktop machine !
If it's a laptop the most likely cause is a build up of dust and fluff in the fan and air vent.  You should be able to see the fan running from underneath the machine and feel warm air being blown out of the vent.  I used to give the vent a quick blast of air which often caused a wad of dust and fluff to lodge in the fan.  At this point you have two options.  carefully pick the fluff out with a fine pick or take the machine apart and disassemble the fan and heatsink to clean it.  Not too difficult but finicky.  When disassembling the heatsink there will be thermal pads and possibly white thermal compound in various places. Don't wipe this off, just redistribute it with your finger.  The soft thermal pads must go back in exactly the same place as they came from.

If the machine is a desktop it gets a little more complicated.  The problem could be heat related, in which case it is a matter of removing the heatsink and fan assembly thoroughly cleaning off all the old thermal compound and replacing it with new.  You cannot buy the "phase change" thermal material that is probably on there. I commonly use "Artic Silver" which you can buy from Maplin. The little tube contains 5 grms but it only needs a blob about 3 mm in diameter under the heatsink.

The other possibility is "Bad Caps" A google search will give you lots of info about this.  It's not an impossible job to do a bad cap replacement, just tedious and you will need to buy the correct replacement capacitor types.

Hope this helps sort your problem.
 

[John Rudd]

Ohh.....gawd...yup I should have said its a desk top unit(Compaq).....
I think its due some tlc....tomorrow so no shop time for me....
I have heat sink compound (I use it a lot doing electronic repairs you know...   ) just hope I can get the CPU out without too much blood loss....

[BaronJ]

Hi John,
I made a lot of assumptions there.

Depending on which model Compaq, there are four screws holding on the fan to the heatsink.  They have to be removed before you can get at and remove the heatsink.  If it is a thermal problem the heatsink will lift away without too much difficulty.  Use a soft 3/4" paint brush to get rid of any dust and fluff first.  ( I actually use a pastry brush !  I don't think the wife has missed it yet  )  The last thing you want is any dust under the heatsink.
Some compaq machines have plastic ducting as well, that should come away with little difficulty. (Clips and/or screws).  Other machines have the fan fastened to the rear of the case and have a plastic duct.  These are easy to get at the heatsink once the duct has been unfastened.  Once you have cleaned everything carefully check all the capacitors for bulged tops or electrolyte leakage around the CPU and in particular the memory power supply.  The majority of intermittent problems are caused by bad caps.

HTH.

[vintageandclassicrepairs]

Hi John,
My desktop (Dell) threw a similar fit recently
I tried a lot of the suggestions given, no joy
In desparation I tried another keyboard and mouse, and it worked again,
I have not yet had time to look inside the keyboard but suspect the problem lies within

Regards
John

[vtsteam]

One more possibility, too, check the power cord and its connection at the power supply. Wiggling it sometimes shows up a problem. Generally it's laptops that get their cord kicked, but sometime desktop power supplies can develop a problem.

Also there's a line into the main power cord connector on the motherboard that's a signal line from the PS on/off switch. If the contacts on the connector are getting dirty, that signal can be intermittent with heat.

Another cause, can be a cracked solder joint on the PCB where the CPU or memory sockets join. The board heats up expands the crack and the computer crashes. This kind of thing usually happens to specific models of computers, and so gets reported online enough that you can usually find references to it if you look up your model. I've seen it for the CPU on Asus boards, and on RAM for several models of older IBM Thinkpads.

[David Jupp]

Odd PC problems I've suffered from having similar symptoms.

On an a Dell - turned out to be known issue on the particular model range - the processor chip lost contact with some connections of the BGA socket as it heated up.  Solution in this case - jam a lump of cork between top of heatsink and case lid to put downward pressure on CPU/socket.

On a homebuilt PC - one 12v line of power supply failed, machine would get part way through boot, but when attempting to spin up the hard disks would re-boot (continuous loop of re-boots follows).

[awemawson]

My main workshop desktop (Compaq Small Form Factor DC7600) did exactly as yours is doing a couple of weeks ago. After a bit of faffing around I proved it to the Power Supply. Blew it's dust out, checked for dry joints / exploded caps etc all to no avail so it ended in the bin. Fortunately I have a pile of DC7600's so could just pull a PSU from another one.

[John Rudd]

Here's an update......

I'm currently typing this on the pc..so hopefully if its sorted then I'll have successfully posted this...

PC stripped to barebones, power supply out, case fan out, memory dimms/cpu with heatsink removed. Removed hdd and dvd rom drive leaving just the mobo in place.
Firslty examined the power supply, no bulging caps or toasted pcb....just a bit of dust nothing to write home about...
Quite impressed actually its not your usual power supply...Has PFC and uses one of the 3842 series of switchers as opposed to the usual Half Bridge type that usually commits hari kiri....
So psu  blown out and fan cleaned, re-assembled ready to put back.
Case fan cleaned up...no drama there.
Took the base unit to the garage, blew out all the dust,checked the caps on the boar, all appeared.
So onto re-assembly...
Slotted hdd and dvd rom drive back, added dimms, hooked up the drive cables, added psu.
Final leg of assembly, cleaned up top of cpu and mating face of fan/heatsink...Applied a liberal coating of my trusty Servisol heatsink compound....fan assembly re-bolted onto cpu, plugged fan into mobo, refit front panel and close up.

All hooked up to the peripherals and working fine so far...

Lets see how long before another drama unfolds.....

Thanks to all contributors for their thoughts and experiences and a Happy New PC Year...

[BaronJ]

Hi John,

I hope you weren't too liberal ;)

"Applied a liberal coating of my trusty Servisol heatsink compound."

Glad you got it sorted 

Happy New Year