CD, DVD, and FD Drive LEDs are OFF and drives won't open

[erndawg]

I am hoping someone will recognize the symptoms I described. Specifically, the fact that the CD, DVD, and FD drives are inop and their LEDs do not illuminate. Yet, there *is* correct +12 VDC and +5 VDC at the Molex connectors and of course the fans spin. No POST, but CMOS battery checks good at 3.1 VDC

I wonder if anyone knows what actually turns on the drive LEDs. I always thought that as long as you had the +12 and +5 volts at the Molex connector, the drive LEDs would be lit and you could open the drive trays. Anybody know this? MechBGone perhaps?

 

[imported_Phil]

If the drives detect a faulty IDE interface, they will usually shut themselves off. Unplug their data cables and they should start opening and closing their respective trays.

Any beeps from the motherboard? If not, check the motherboard, processor and power supply.

 

[FlyingPenguin]

Are you SURE the 5 and 12 volt rails are working? Have you put a digital multimeter on the rails on one of the drive power connectors to confirm and that the voltage is correct (within 5%)?

I doubt it's the IDE interface. You can pull the ribbon and the drive doors will still open and close as long as there's 5 and 12 volts.

If it doesn't open with the ribbon in and it does with the ribbon disconnected then the problem is that the mobo is locked in reset - it's sending a reset signal to all the drives and not releasing it.

Could be something as simple as a shorted reset switch. Pull the wire for the reset switch off the mobo and maybe you'll get lucky. Otherwise I would suspect a dead mobo. There's not much else that can hold the reset on.

This a new build? If so you sure there's no standoffs under the mobo in the wrong place shorting it out? Maybe a loose screw wedged unter it?

Hope this helps...

 

[erndawg]

Thanks Phil. No POST beeps. We built this PC 6 months ago, and it has been working well until now. I know the usual suspects for no POST beep, but I thought it unusual that the drive LEDs were OFF. I was sure they would be lit if +5 and +12 are good; which they are.

 

[erndawg]

Thanks FP. The +5 and +12 supplies are exactly the same as what they were when measured with a Fluke DMM 6 months ago when we completed the build. No standoff/ clearance problems for the MOBO backplane. And neither is the reset switch shorted closed (pulled it). We pulled one of the IDE cables and that drive *did* come to life. (That is, the LED lit and the drawers would open and close when commanded.)
So, what next? Any recommendations? I'm not afraid of getting into the problem; I'm an EE and know a few things. Thanks again for your input.

 

[FlyingPenguin]

We pulled one of the IDE cables and that drive *did* come to life

Dead mobo then, or could possibly be a nother device is shorting the reset circuit on. I'd pull the mobo out of the case, set it up on a bench. Connect only a video card and the PSU and turn it on (you can just short the power switch pins with a screw driver to turn it on).

If it POSTs then the mobo is fine and soemthing else is to blame. Start connecting things one by one until you find the culprit.

Hope this helps...

 

[daveybrat]

sounds like a dead motherboard to me too. You'll have to unplug all the ribbon cables from the motherboard and try again.....but it still sounds like a bad board.

 

[mechBgon]

Ooops, sorry not to notice my nickname in the title for a while, I was distracted by a huge pizza :Q But yeah, what the guys are suggesting, peel that thing apart and try an out-of-case benchtest.

The only other thing I can add is that if you list your full specs, that can help bring out the insights sometimes. Is the PSU a good-quality unit with adequate wattage for the load? Being an EE, I suspect you didn't skimp on that, but even good brands have their defect units, so if you have another good PSU around, you might try a swap also.

 

[erndawg]

Thanks mechBgon, flyingpenguin, and daveyrat. I looked a little more closely and made these observations: All voltages on the Antron PS look great (within a couple % of nominal) when everything was connected. I did not measure Vcore, which I believe? is developed on the MOBO. Now I have only the MOBO, PS, CPU and speaker connected. Still no POST beeps. (I start the PS with a screwdriver.)


So, how do I determine whether it is the CPU or the MOBO? Other than swapping a known good CPU or MOBO (which is not an option for me), what can be done to see if the CPU has a heartbeat?
I noted that the CPU Heat Sink is cool to the touch, but a large transisitor (Q15) on the MOBO is quite hot. BTW, the CPU is an AMD Athlon 64 3200+ and the MOBO is a Soltek K8AN2E. Any thoughts?? Thanks again for all your input.

 

[daveybrat]

When you aren't sure if it's the cpu or the motherboard, it's always best to assume the motherboard. The odds of it being a bad cpu are 1000 times less likely than the motherboard itself. In all my years of repairing pc's, i've only had like 2-3 legitimately bad cpu's and hundreds of bad motherboards.

 

[FlyingPenguin]

I'm with Davey. It's VERY hard to kill a CPU. You can safely assume the mobo is dead. Short of that the only way to be SURE is to put the CPU in another mobo.

The only time I've ever seen a dead CPU is when a client takes a power surge or the PSU blows and fries everything else with it.