I'm looking for some good web sites about troubleshooting failed PCs.

This afternoon my new HTPC won't boot. I had the PC powered on this morning for about an hour. I performed a normal soft shut down this morning.

Motherboard is Asus M3N78-EM. PSU is a Seasonic SS-300ET 300W PSU. AMD 5050e 2.6 GHz Dual Core CPU.
2 GB PC-6400 800 MHz DDRII RAM.

The system is all new within the past few months.

The symptoms:

Motherboard +5V LED is ON.
Power switch LED is ON.
Hard drive LED is ON.
PSU fan spins.

System starts to boot and then stops. The CPU cooler fan and chassis fan spin for about three seconds and then stop. The system repeats this behavior.

System never gets to POST and never displays anything on the monitor.

I pulled the only internal card (PCI TV capture card), disconnected all drives and all external peripheral connections. Same results.

I pulled the primary hard drive and installed into my office machine. fsck reported no problems as well as some random checking/mounting of partitions.

Some quick browsing of the web indicates the problem is the PSU or motherboard, but I knew that much before surfing.

The least expensive blind guess solution (but not by much) would be to replace the PSU, but some troubleshooting would be nice.

Thanks much.

Good troubleshooting so far! It's always a good idea to start with the bare minimum amount of equipment/devices when trying to track down a hardware problem.

Usually if you're not able to get any kind of BIOS beep codes it's a sign there's a possible issue with the motherboard, power supply, or CPU.
Does your case have a PC speaker connected to the system board? If so, that could help a bit. If not, check on the system board documentation; many modern and/or small-form-factor system boards have an on-board PC speaker...

I would unplug the power, then remove the memory, restore power, and attempt to boot it. If you still don't get any kind of BIOS beep codes on the PC speaker, it's worth trying the power supply next (after reinstalling the RAM). If you do get beeps out of the system with no memory installed it could be one (or both) of the DIMM's.

Hopefully it's not something as serious as the system board or CPU.


Good luck!!

No speaker installed but I will swap one from an older box and try that.

Hi

strick1226 is absolutely correct.
Initially setup the system with no adapters, no memory modules, a speaker connected, and the PSU connected only. If the motherboard and CPU are OK then the motherboard should start and the BIOS routine responsible for testing RAM should fail the test resulting in a beep code from the speaker.

I've had a look at an image of this motherboard on the net, it appears to have BOTH an ATX PSU connector AND a 4-pin auxiliary PSU connector. If the 4-pin auxiliary PSU connector is not connected to the motherboard then the motherboard will not power up normally.

Should this base test fail then it indicates that either the motherboard, CPU, or power supply are at fault. It is possible to test the power supply with the use of a multimeter (connect a device to the PSU as a load (eg. hard disk or floppy disk drive), bridge the "power-on" pins on the ATX connector, and then use the multimeter to test the supply line voltages) - of course only perform this type of test if you are suitably skilled and experienced).

Following that the next logical step is to replace the PSU, then the motherboard or CPU.

Apart from the auxiliary 4-pin PSU cable, it would also seem prudent to check that the CPU is correctly seated, and that there are no other extraneous factors such as motherboard shorts to ground (if you have installed the motherboard in a non-compliant case).

The remaining possibility is that the Motherboard BIOS, or user specified BIOS settings has become corrupt. Using the information in the motherboard user guide (available online) reset the BIOS settings and re-test. According to what I have seen on the net this motherboard is equipped with ASUS's CrashGuard technology to allow recovery from corrupt BIOS. It is extremely important that if you suspect that you need to flash the BIOS that you read ALL of the BIOS recovery information for this motherboard before proceeding to turning the motherboard into a useless "brick". If the motherboard is under warranty I suggest that you take it back to the supplier for a test/BIOS flash rather than do it yourself.

Hope that helps.

Chris

Today I was able to continue troubleshooting the box.

I installed a PC speaker. No boot code beeps.

I checked PSU voltages. All looked okay. I bought a generic PSU to help troubleshoot but witnessed the same behavior. That more or less eliminated the installed Seasonic PSU as the problem.

I cleared the BIOS. Same results. I'm presuming there is nothing wrong with the BIOS.

The system always boots and restarts three to four times before the fans remain on.

I'm reasonably certain there is nothing wrong with the RAM. When I removed the stick I heard the expected boot beeps. Yet with the stick removed the system exhibited the same three to four restarts before the fans remained on. Reinstalling the stick resulted in no beeps and no booting and the same three to four restarts before the fans remained on.

That leaves the motherboard or CPU as the culprit.

I reseated the RAM stick, tried different RAM slots, reseated various connectors, and tested the case power switch. No change in the results.

Oddly, after several minutes of poking around earlier today, suddenly the speaker beeped and the system booted.

I rebooted several times with the keyboard and reset switch. Each time the box booted. Then I powered down and also opened the PSU switch to completely remove all power.

The box again became stubborn about powering up correctly, although eventually the box booted several minutes later.

For a while the general pattern seemed to be that once the motherboard booted, the system would power up from warm shutdown or reboot. The catch seemed to be as long as I did not fully kill the power supply by disabling the PSU switch or power cord strip switch. That is, as long as I maintained +5V standby the system seems to boot or reboot okay.

When I fully removed all power then the system booted correctly only about 5 to 7 minutes after powering up. When I first powered up from full power shutdown, the system repeated the original act of booting and shutting down by itself about three to four times before staying powered up. There was no video signal until I rebooted about 5 to 7 minutes later.

Once available, the video display (DVI or RGB) tended to freeze or go berserk.

Another oddity is that pressing the case reset switch caused the system to power down as though pressing the case power switch. That is, the fans stopped and the system seemed to have stopped.

As another test, I disconnected all fans. Several minutes later the CPU heat sink was warm to my touch. That is inconclusive, but seems to indicate the CPU is working. As I no longer have integrated video or BIOS beeping, I suspect the northbridge chip might be history. At this point I think the motherboard is the problem.

Yet after a few hours of this, I no longer could get any video signal or get the system to boot. No beeps. The fans would spin with the usual three to four shutdowns, but nothing else. Whereas earlier today the system seemed temperamental and intermittent, the system now seems broken.

I suppose the next question is whether to order the same model motherboard or something different. The Asus M3N78-EM seems highly rated as a HTPC motherboard, but perhaps I ought to consider a different model or brand.

It sounds like a lack of pwoer at boot time. The PSU may not have enough watts to power everything at full wattage. The servers I work on have a high power demand at iinitial turn on for about 5 to 10 seconds befor it kicks down to normal power usage. Those 5v+ that you have is what you could be lacking during the intial boot when you do a true cold boot. try kicking up to about 350 - 400 watt PSU and see if that fixes it.

I don't think the PSU rating was at fault or I would have seen the problems from the beginning. The Seasonic is 300W and the generic PSU is 350W. Both provide more than enough juice for this setup. I had the box connected to my Kill-A Watt many times and never saw a draw that exceeded the PSUs, even at initial power on. Not even close.

The troubleshooting I performed this afternoon was with nominal load --- the mobo, RAM, CPU, and fans. Same boot problems with both PSUs.

Everything was working fine for three months before the recent failures.

I still suspect RAM could be the problem. Are you sure you don't have a spare RAM stick to test it out with ? I always keep one around that I know works.

I don't have a spare stick, but I have two 2GB sticks installed in my office machine. I used one of those and saw the same results. I tried two different slots.

There no longer is any response at all. Just the triple restarting of the fans and then nothing. No beeps. No video. That would imply a bad northbridge chip or something associated therein.

I would have been tickled to report otherwise. I'm ordering a new motherboard this week.

I suppose there is a slim chance the problem is the CPU. I could swap CPUs between machines, but I prefer to leave sleeping dogs lie and not mess with my office box any more than necessary.

Well I guess you're right then, the only things left are CPU and mobo. I'm betting on mobo. The CPU is usually the last thing to go. The capacitors on the mobo are usually among the first.

It seems it is the power supply in the motherboard that is the problem since it has an issue with heat. If the MOSFET are warm or hot, the system boots up. If it is cold, it does not boot up. If this is your case, your motherboard is defective. You can test it if it is a temperature issue by using semiconductor cooler spray and spray the desire MOSFET. If the system is booted up, it should halt or power itself down when the devices are sprayed for a defective board. A normal board will keep on working.

Initially I might have thought the same. As I shared earlier, by the end of the afternoon I no longer had any video or BIOS display, even after many minutes. Only the fans spinning. Right now the motherboard is no longer functional to even get to the point I enjoyed earlier in the afternoon.

Have you tried booting from a Live CD? Based on what you've described, unfortunately it sounds like your mobo may be shot. (It's pretty much the same experience I had when mine died)

That said, you may want to consider a slightly heftier PSU. 300W seems a little on the small side.... personally I'd go with 450 or 500W.

IMHO its the mobo, and the ram is highly suspect. I would sell the ram and buy a new mobo and ram.

Would you believe that running pirated windows XP can cause the same symptoms? I didn't either until I saw it happen with my own eyes.

Hi,

You are sure that the HSF is mounted properly? Remove and reapply compound for the processor if not a manufacture original heatsink.

I would bump the PSU to a minimum of 450W for a rig in use today. You're not going to save much by using minimal design criteria for the PSU. Just looking at the rails will not indicate a problem when it's due to load as that load will vary. You won't be able to see the differences with a VOM/DVM unless you monitor the current and voltage across a period. A good DAS would be useful but most benches don't have one.

Look at the capacitors in the MB supply section for possible damage. Leaking, bulging or discoloration of the caps as another potential problem.