Confirm diognosis of bad motherboard

Working on a clients 1997 Dell tower running Win 95 that goes through a normal shutdown to the "It is now OK to shut down your computer" screen and when you push the power button the floppy starts a pronounced continual clicking which can only be stopped by pulling the power. Second symptom is the machine will turn itself on unattended at random time intervals with no outside input.
My first thought was a failing floppy as unplugging the floppy immediately stopped the noise, but a new floppy did nothing to change the pattern. Also noticed that with the floppy unplugged the shutdown symptoms changed slightly, all is normal to the "OK to shut yada, yada" except that when the button is pushed it seems to shut down for perhaps a second or two but then the fans resume spinning and both the green power and reset lights are dimly lit.
I swapped both the power supply and the power switch out of a known good Dell tower again with no change in symptoms. I then took a spare hard drive and installed it and reformatted and did a fresh install of Win 98 to eliminate any software issues. I also used the windows troubleshooting panel inside the system properties>file system properties to disable every option there again with no change.
At this point I feel I have exhausted most of the hardware & software issues except the motherboard and Dell tech support agreed with me and I the client has ordered a replacement tower for $500 as I advised him that I did not think the cost of replacing the motherboard was justified and he is OK with that.
Somehow however I keep looking at this tower and thinking that with the exception of the two symptoms (no reliable shutdown and unattended startups) the bloody thing runs just fine. I have this nagging feeling that there is something I am overlooking, can anyone offer any suggestions?

 

Howdy neighbor and welcome to the board

When you press the power button, have you been holding it in for 5 or 6 seconds? Some ATX systems will go into a sleep mode if the power button's just pressed once, holding it down for a while normally shuts the system off.

For the self-start problem, check around in the CMOS settings in the Power Management area. There may be a setting or two that tells the system to power on when the phone rings, power on at a certain time etc.

The clicking floppy drive may be caused by the sleep mode and/or a virus scanner that's set to scan the floppy drive at system shut down.

 

reply

Well Howdy back at you neighbor, wow American canyon that is close by. Thank you for the welcome and taking the time to reply.

Yup, I tried both the quick push and extended push of the power switch for soft power type affairs. No difference, when this thing goes into this clicking cycle nothing short of pulling the cord shuts it down. Interesting that this old of a unit is without question an ATX board, but there is no soft power feature that I can determine or else it is not working, my Dell just shuts down but I have Win 98 and I am not clear if the screen "it is now safe to yada, yada" is determined by his Win 95 or the power features of the hardware.

I did spend several hours poking around in CMOS and trying different combinations of settings none of which changed a thing. I never did find a setting specifically addressing power management in his CMOS, and I know what to look for because I have changed it in my Dell. His is an older model and I don't recognize the CMOS and right now can't even remember the name. I do plan on going back to the CMOS one more time since that is the only thing I have been unable to eliminate by swapping parts with my Dell.

As to the clicking floppy and a possible sleep issue or virus I think I pretty much eliminated that. The first thing I did was set the sleep parameters to never, and on the virus issue which I thought of and Dell also mentioned I think that putting in a different hard drive and reformatting it and doing a virgin install of Win 98 with no traces of virus protection that issue can be ruled out.
Again thank you for your response and if you have any further thoughts I will be appreciative.

 

Have you tried replacing the power switch itself, and checking the connection where it plugs into the MB? Could be bad contact or a sticking switch.

 

reply to orndog

Yup, as I said in first post I swapped both the power supply and the power switch from my Dell no change in symptoms. Thank you for the thought however.

 

Maybe clearing the CMOS or setting it to the default values?

There're a few ways to clear the CMOS, post back if you need some tips.

Probably the power features. If I remember correctly, with a correctly configured ATX system, Win95 will shut the system off just like Win98.

Just for the heck of it, you should be able to find a add-in card that has a floppy controller on it. Install that card, attach the floppy drive to it, disable the onboard floppy controller and see what happens. Might want to try another floppy cable too, if you haven't already.

 

Reply to Cliffh

Thanks Cliff I will try defaulting and/or clearing the CMOS, think I can find the info in CMOS or my M. Myers A+ book. Will look around for a controller card. Thanks for a new thought on this perplexing thing.

 

Just sent you an email regarding the floppy controller card.