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Pc broken

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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:

--- Quote from: John Rudd on December 31, 2014, 12:28:36 PM ---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?

--- End quote ---

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... :scratch:  :zap:) just hope I can get the CPU out without too much blood loss.... :lol:

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  :bugeye: )  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 :scratch:
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

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