ASus A7N8X-LA - Powers on, but no boot (solved)

[socketa]

After replacing the battery i got this board to boot.
Went back to it a week later and only the cpu fan spun after powering it up
So i changed RAM, and blew out the slots to no avail.
So then changed the psu and noticed that the keyboard lights blinked briefly (which they didn't do before)
Tried again a few times and no keyboard lights.
The fan would occasionally stop a few seconds after turning it on.
So felt like that it was doing what it was supposed to do, so i took the heatsink off, and it was dry underneath.
Put new paste on, and it booted first pop.
It seems that the CPU 'shuts down' but the fan keeps going - which can be quite misleading, because i thought that when the CPU 'stops' due to overheating that the fan would stop as well.

[piernov]

Re: ASus A7N8X-LA - Powers on, but no boot (solved)

Repasting was just a coincidence I think. Or there may be a bad contact in the CPU socket and taking off/putting back on the heatsink did something.
No sign of bulging capacitors? (they could still be bad though)

[socketa]

Re: ASus A7N8X-LA - Powers on, but no boot (solved)

OK - yes, i did also remove the CPU and give it a scrub with a toothbrush and dishwashing liquid. So maybe that was the problem - there was a small area of whitish mould(?) on one corner. Now i'll never know
No bulging caps - that's one thing that i like about it - zl and mbz.
Coincidentally, it did start playing up (turning on and off by itself)- but that was due to a faulty power button, that i fixed with a wd40 type aerosol).

[socketa]

Re: ASus A7N8X-LA - Powers on, but no boot (solved)

This was going good, up untill now
But it started to make crackling noises from the small onboard speaker, and there was a series of BIOS beeping also - (forgot take note of the sequence though).
Couldn't get it to boot again, although the power light and cpu fan turned on.
I probed around on the coils and vacant cap spots and all were giving, what looked like to me, reasonable voltages
So tried three other CPUs only one got hot, the others didn't.
After a few tries with that CPU (not booting) it now boots again, with no crackling.
What was a probable the likely cause of the cracking
Dirty contacts in the CPU socket, as previouly suggested?
Would it be a good idea to spray the socket with mould killer, and then detergent and then rinse it out and dry?
Also Windows in not detecting the Realteak ALC650 chip - can i test if it's faulty? There is 2.4V on the Line out L and Line out R pins of the chip, so it at least has some life

[socketa]

Re: ASus A7N8X-LA - Powers on, but no boot (solved)

It started cracking again and windows restarted a couple of times - then the board failed to boot.
It was still crackling after i powered it up, and also when i reinserted the cpu a dozen times or so.
Then it stopped crackling and still wont boot - so i'm assuming that whatever weak connection there was, is no longer making contact.
Am going to wash the socket, starting with dishwashing liquid, then mould cleaner, then, if no luck, something like wd40 or engine degreaser. Although i'm still not sure that it's the socket.

[momaka]

Re: ASus A7N8X-LA - Powers on, but no boot (solved)

If I am not mistaken, this board has an nVidia nForce 2 chipset. Although fairly reliable, I do remember reading some posts on here that said even nForce 2 chipsets can fail in a similar way that the nForce 3, 4, and onwards chipsets failed from the bumpgate issue.

I suppose washing the board is a good first start, though. I don't suggest spraying anything corrosive in the socket. Wash with hot water and dish detergent is OK, as long as you get all of the detergent well washed and the board dried quicker (i.e. don't leave it in some dark corner where it takes the moisture many days to dry, as that can cause corrosion on the contacts.)

If this doesn't work, then perhaps the NB chipset may be going bad. In which case, try applying some pressure on the NB heatsink first while trying to boot the board. Try this several times at different pressures (but don't go overboard.) If that doesn't do anything, try the same on the SB too.

Finally, if this was a used board you bought/got from somewhere (i.e. not original owner), then make sure to do a thorough inspection for scratched traces and damaged SMD components. I repaired a Soyo socket 370 motherboard last week that had damaged SMD array resistor by the CPU socket. I don't know if the board worked before fixing this (I don't like to test equipment that I can see has bad components that may be critical to the operation), but the board was given to me in "as is, for repair" condition. So after fixing that SMD resistor, the board worked perfectly fine. Chances are high that it didn't before... or perhaps it could have been very intermittent like yours.

[socketa]

Since my diagnostic card wasn't showing any readout, i figured that the BIOS wasn't being read.
Flashed it, but the board still doesn't POST
There is a hard short to ground on the BIOS Vdd power supply pin,
Which could mean that the chip is faulty (which is unlikely since i had no problem flashing it), or there is some shorted component.
I checked a couple of schematics of similar boards, and the BIOS chips are powered directly from the 3V or 5V rails...hmmm,
But the 3V or 5V rails are not shorted to ground on this board

[socketa]

That was probably because i put the chip back on the wrong way around
... to be continued

[stj]

lol
btw - never use wd40 on electronics.
it's only for keeping water out of mechanical stuff outdoors.
if you need a lube then use 3in1
if your cleaning contacts use contact-cleaner

wd40 can destroy pcb's slowly.

[socketa]

Well, it wasn't the bios.
Pulled of the bios and reprogrammed it
And eventually (after winding up pulling off 5 pads and 2 traces after trying more than ten times to install common plcc32 sockets with hot air, got lucky with obtaining some better plcc32 sockets, and this time putting solder paste on the pads before placing the socket on the pads and using a fine tipped iron and a microscope - which worked out very well
To secure the pads i used some chinese locteft 272, which is supposed to resist temperatures less than the melting point of leaded solder, and sets in the absence of oxygen,
cleaned up around the pads, and used uv solder mask the next day
Then put the bios chip back in and it went right into the bios screen, but froze, IIRCC, not long after subsequent attempts just got less through the POST sequence, until 0000 was just displayed on the PCI analyser card
So decided to inspect the board and nothing seemed to be visually detached or area of discoloration due to overheating.
Then tried powering it on while moving a couple of VRM caps, and some digits appeared on the analyzer card
After lots of pushing around on the surrounding area occasionally some digits would be displayed
So moved to near the southbridge area, which was on the opposite corner of the board, and started pressing down on the south bridge and the i/o chip, and now eventually the board boots (for the meantime at least)
So now it's looking more and more like the nForce2 southbridge. as pusing down on it can get the board to go through the post sequence by pushing down on it quite hard
If i release the pressure when it goes into bios screen i can still move from one bios screen to another, and see that the hardware monitor is still active, but sometimes can't shut down with the power button
Also it won't even turn on sometimes on without pushing down on the southbridge
Which would it more likely be? - The chip itself, or a BGA spot not contacting one of the the pads?