Help fixing a broken PC

[MrScott]

Hi, I'm in the process of diagnosing / fixing a seriously dodgy PC and I need a second opinion or 2. The machine is a Duron 850, 128MB of SDRAM, some generic looking motherboard running WIndows 98.

Problems when i first got it:

IE / windows explorer not working (fixed)

After about 5 minutes the PC would stop outputting a graphics signal, and not POST again unless left off for about 45 mins.

First thing I thought it was overheating, so I stripped it down, cleaned & reseated everything. It ran for a few hours fine whilst fixing the software problems, then when I left it to defrag I came back and it had stopped responding with no monitor output, same as before.

Thing's I've tried:

HDD diagnostics - fine
Memtest - Found errors which I've now fixed, also tried different RAM
Different PSU - no change
PCI graphics rather than on board - no change

Once it has cut out sometimes it will show the initial POST screen then die, sometimes it just spins up fans but no beeps / screen output. Also sometimes the screen will be woken up but have no picture.

It still looks kinda like an overheating problem as it ran for longer after I'd cleaned & reseated everything, but the heatsink doesn't feel hot enough for it to cause crashes and I've completely cleaned & reseated it with AS5. On the other hand I'm very tempted to blame the old / rubbish CPU / mobo combination, and I was going to recommend basically a rebuild (new mobo + cpu + ram + gfx). I don't know whether to try out some different cooling, maybe a different HSF or running Prime whilst watching temps first, or if that would be a waste of time. (I'd much prefer not to and just rebuild the damn thing). What do you guys recon?

 

[xirokx]

was the replacement you tried higher or lower wattage compared to your current one?

do you have saving options enabled in control panel, system, somewhere around here you will find power options, what is it set too?

if you right click on my computer icon, then select manage, then select system to view "events manager" what error msgs do you have there?

you can try priming it and seeing at which point it cuts out or how soon it cuts out...

IMO I believe if it was a bad cpu/mobo combo it just wouldnt boot? presuambly you have been using the system for a while before this started happening?

I reckon its a PSU problem....because you tried a diff GPU and everything else you say is suggesting its power related...

 

[MrScott]

Hi, thanks for the reply. Yes this is a problem which has developed with no other changes to hardware.

I've set all the power options to never go into standby / turn off monitor to make sure it wasn't a problem with standby.

The other PSU I tried was slightly lower wattage I think (old one i had lying about), and it still had problems with either the original or test PSU only plugged into the motherboard (no drives, etc), and they should be able to handle a Duron 850 (The test PSU I'm using was running an AthlonXP system a few weeks ago with no problem). I've also got a multimeter on the PSU and the voltages seem within limits and stable enough not to cause a problem.

I can't check event viewer cos it's Windows 98 so it doesn't have one.

I've tried running Prime on it, it didn't cut out whilst priming (although I didn't run it for that long), the only times it's done it since I reseated everything is when defragmenting the HDD.

I might try running it off a spare HDD running XP and maybe with a different PSU again, and if it is a PSU problem when I replace cpu / board / gfx then the problem should still show up. The only thing that makes me doubt that the PSU is the problem is that after it cuts out, it has to be left for nearly an hour before it will POST again, and during this time swapping PSUs makes no difference and it still doesn't POST. The reason I'm pointing the finger at board / CPU is really a process of elimination at the moment.

 

[leezer3]

Sounds like a toast board. Does it have a NB fan, & if so is it running?
Oh, try a different battery as well. While I don't think a flat battery would cause these problems, its worth a try.

-Leezer-

 

[MrScott]

Hi, NB is passively cooled, heatsink cool to the touch. I've now rebuilt it, so new CPU / board / gfx / memory, (with parts I had around) and not too surprisingly all is well. Thanks guys.