Repair.IT, Replace.IT – Paging PC not booting

On Saturday, a PC was delivered to me – an urgent repair job.  The PC has an 8-port serial card in it and is used to send messages to pagers – yes, pagers are still being used.  Anyway, the symptoms described are that it keeps rebooting – which very much sounds like hardware, but can be software.

On closer inspection, I noticed that a number of capacitors on the motherboard were bulging, a sure sign of over-temperature which causes the electrolyte inside to become pressurized almost to the point of opening the vents – some were open, you can see the dark marks on top of the can.  Anyway, replacing the capacitors is really not an option, hence a replacement motherboard is required.  I proceeded to check the motherboard model and found that it has a LGA775 processor.  Luckily there is still one motherboard available – a Gigabyte GA-G41M-Combo which will work, but it has DDR2 or DDR3 ram.  The old motherboard had only DDR ram – one 256MB module.  Anyway, as I would have to wait until Monday to obtain the parts needed, I thought I would power it up anyway.  It wouldn’t power up – or rather, it wouldn’t stay powered up.

I removed the power supply and connected my PSU Tester – it turns on then blinks off.  Ok – a power supply is also needed.  I connected my test power supply and proceeded to power up.  I can see the bios screen come up, but pressing Del on the keyboard doesn’t go into setup – strange.  Anyway, I see that it goes a little bit, then a beep and it resets again – so this is the symtom that the customer reported.  I proceeded to remove the heatsink, and processor – which was an Intel Celeron D 346 running at 3.06GHz.  It was then that I saw more capacitors that had failed, hiding under the heatsink.


Sharp eyes will see three on the right of the cpu socket, then a few more spread around the heatsink in the middle of the motherboard.  On Monday, I went out and picked up the new motherboard and a new 550W power supply.  Then I went out mid morning and disaster struck – my car broke down, overheating.  The car isn’t really part of this story, but suffice to say that 4.5 hrs later, my car has been towed to my local motor mechanic and I am home, having a cup of coffee and a sandwich.  Back to work – I proceeded to install the processor, using Arctic Silver 5 for the heatsink compound.  Don’t forget that I am reusing the cpu and heatsink, so have to clean all the old thermal compound off, then tint the cpu top and heatsink, then a smidgeon of Arctic Silver 5 – supposed to be 2.5 cubic millimeters or about a grain of rice.

Installed two pieces of 256MB DDR2 ram – double the original ram, will make it work better, but obviously it is only running a simple application so it isn’t necessary to have more memory.  Installed the power supply – connected up all the cables to the DVD-Rom, floppy drive and hard disk drive.  Power up – keyboard not working, USB mouse not working – ok, what gives?  Power off then back on – same thing.  It seems that the keyboard doesn’t work.  I have a spare PS/2 keyboard somewhere – ok, got it and tried again – good, my keyboard is working, but mouse isn’t.

Windows XP Professional – with a change of hardware will require reactivation.  Choose not to, because the network isn’t working.  I try to eject the dvd-rom, but nothing happens – it has failed too!  I downloaded the network driver from the Gigabyte website, since for some reason, the supplied driver cd won’t read on my laptop – then put the driver onto a usb flash disk, and used that to get the network driver installed.  Continue with driver installation – there are lots of drivers needed, eventually I got most of them done, then had to find the video driver, sound driver and last of all – the drivers for the Decision PCCOM PCI 8 Port serial card, which I can’t seem to find quickly.  No choice then but to get Windows to tell me which driver is wanted, then copy it out of the windows folder and point the hardware install to that location, and keep doing this for the other 8 files needed.  The drivers were already there, so I just had to find them and put them somewhere for windows to copy again.

So, a couple of hours later, everything is updated – Windows wants to install some XP updates – so agree to them, and eventually got it updated except for SP3 – I decided not to do this, because sometimes applications stop working when that is installed.  Oh, by the way, the floppy drive also had failed, but luckily the hard disk drive was still working.  How about that?  Power supply, motherboard, dvd-rom drive, floppy drive and keyboard had failed.  The USB mouse eventually worked after the drivers were installed – weird.

Final word – the Paging PC has been Repaired, with mostly everything in it Replaced – so that was “Repair.IT” and “Replace.IT“.

[Note] I think that the power supply was starting to fail – maybe introducing a lot of ripple onto the supply lines, which caused the capacitors to overheat – because they are trying to smooth the DC voltage.  Then eventually the power supply failed more such that the keyboard, dvd-rom and floppy drive was destroyed.  The USB mouse was still ok, so that only uses 5V and the drives use 12V – but why the keyboard – I can’t explain that.  So eventually the power supply failed completely and stopped turning on – at least for me.  The DDR ram might still work, but I need to find an old computer to test it.  When I get a bit of time, I may go through the exercise of replacing the failed capacitors and look at fixing the power supply, but at least the customer is happy now.


Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s