PCI-6224 Dell Optiplex 755 PC Won't boot

[Keith B]

We are using the PCI-6224 DAQ in Dell Optiplex 755 PC's. With the PC turned off we turn on our instrument and the LED on the PC CD drive begins to flash. When we attempt to turn on the PC the power button LED just flashes and it will not boot. It appears we are trying to power the PC through the DAQ card. Some Optiplex 755's work OK. These are all new PCs just purchased from Dell. I have tried using other 6224 cards that work OK in other PC's and our instrument PCB that also works OK with other PC's. We have tried all cables and the Dell PCI slot adapter all from units that work and nothing seems to fix the problem except changing PC's. Has anyone had similar experiences and how did you resolve the problem? I have read some of the other posts about similar problems and they refered to BIOS updates but these PC's were all purchased at the same time.

[Neal M]

Hi Keith B,

I have a couple questions about what is going on:

• Does your system start up correctly with the instrument off? With it unplugged from the computer?
• Is the riser board seated well?  I have seen problems similar to this when the PCI riser board is not seated completely.
• What is your instrument providing to the PCI-6224?  e.g. digital signals cannot provide hardly any current to drive things.
• Have you tried a different PCI slot in the riser?  Does this have any effect?
  

I would also recommend upgrading the BIOS.  Even though the computers were all bought at the same time does not necessarily mean that they have the exact same version of the BIOS. 

Here is a KnowledgeBase that goes over some basic installation troubleshooting steps.  I realize this is kind of generic, but it gives some good advice, including some of the questions I have above.

[Keith B]

Neal thanks for the reply.

We are using 21 digital inputs being driven by HC244 chips on our PCB. We also use 2 analog channels. We do not us any power pins but do use the ground. When our instrument powers up the outputs are active. With the instrument off or disconnected the PC boots up OK and then will run fine with our instrument. If I disconnect either cable from the NI card the PC will boot. The problem is our equipment is used in an industrial environment and has heated dies. Having to turn off the instrument every time you turn on the PC is not a good solution to this issue.

I have tried multiple riser cards, slots, NI cards an PC's. The only thing that seems to fix it is the PC even if it is the same model. Because we ship all over the world we are concerned that even if it works OK here if the PC is ever replaced we will have the problem. Can you explain how we can be supplying power to the PC through the digital inputs on the NI card? I would have thought there would be some type of isolation so that could not happen.

Keith

[Keith B]

Neal,

We did some additional checking today and found that if we disconnect the chip selects on the three HC744 drivers the PC will boot. That is telling us that the PC is receiving power from our digital outputs through the NI card inputs. It seems like other people should be having the same problem. Do you know of any work arounds except having to redesign our PCB?  I did try reflashing the BIOS just to be sure that would not fix the problem. I also found out the problem occurs on both Dell Optiplex 745 & 755.

[AnalogKid2DigitalMan]

Just a thought- could the offending Dell have 3.3V PCI slots versus older 5V style slots?

Don't know that much about the PCI specs or the Dell, just aware that there are different PCI voltages out there.

Edit- upon reading your posts further, I see you bought them all at the same time, so I doubt my thoughts above are invalid.

-AK2DM

Message Edited by AnalogKid2DigitalMan on 03-28-2008 01:31 PM

[BrowningG]

Hello Keith B,

It looks like you are using the digital inputs of your DAQ card with your device under test.  Do you know the states of these digital lines when you try to turn on your computer?  If so, do you know the current draw or source of these lines during the startup state?  I think you might be trying to draw too much current from your computer and I would like to check out your startup state specifications. 

[Keith B]

When I am trying to start the PC the outputs on our card are active ttl outputs. We are driving them using an HC744 chip. We tried connecting an opto coupler on the +5VDC line coming from the card to turn off the outputs until the NI card came up and that worked once. Then it latches because when we turn off the PC the outputs on our card are still on and that keeps the +5VDC on the card high. Any idea why the digital inputs are powering the PCI bus? If we swap a power supply from a PC that works the problem goes away. These are new PC's so I do not think the power supply is bad as it happens on multiple PC's.

[Nick_F1]

Hi Keith,

This is a very strange issue.  Do you know if the card that you are using to provide the signal to the 6224 is a sinking or sourcing signal?  Basically does your card provide a path to ground to create a logical high or does it provide a voltage.  Are you using a TTL signal to provide the signal to our card?  It is possible that if your card is a sinking card, then it is providing a path to ground which is drawing power from the computer.  If that is the case then it is possible that a lower wattage power supply does not have enough power to start up the computer.  Can you tell me the difference between the two power supplies? 

Another possibility is that the setup is somehow affecting the ground plane of the computer.  Can you please let me know how exactly your board is connected to the 6224 and what the specs of the signal are? 

If you could answer these questions I think we'll have a better idea of what is going on and continue trouble shooting from there.

[Keith B]

Nick,

Our instrument output is TTL and does not use pull up/down resistors. We think the 6224 uses a pull down. The Dell 745 has a 280 watt power supply and some of them work OK. We can put up the same 6224 card and riser adapter in a Optiplex 520 with a 220 watt supply and it works fine so I don't think it is a loading issue. I also put the 220 watt supply from the 520 in the 745 and it works. I think that the power supply must have a sense line that is seeing the 3.5 VDC that is coming from the NI card which is keeping it from turning on.  Dell sent me a new power supply and it did not fix the problem so we have to come up with a different solution.

Thanks again for your time....Keith

[Nick_F1]

Hi Keith,

Thanks for the update.  If you have anymore questions, please let me know.