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HeadOnAPike

8 Posts

1007925

January 31st, 2012 18:00

Optiplex 755 only turns on through power supply button, no video output.

So I can't turn on my Optiplex 755 through the regular power button.  I have to hold the power supply test button on the back, and then press the on button.  The computer then stays on, but I don't get any video output.  No BIOS beeps or anything.  Not sure what's going on.  The service tag is

rdunnill

6 Professor

 • 

8.8K Posts

January 31st, 2012 19:00

Power supply problem?

DELL-John C

5 Practitioner

 • 

353 Posts

February 1st, 2012 03:00

Hi HeadOnAPike,

It does sound like there is a problem with the power supply but I've got some steps that will help you determine exactly what is happening. Some of these steps require opening the system so please remove the power cord from the back of the system before doing these steps. If you can answer the following, it would be a great help:

1) Switch the system on. Can you tell me the colour of the power button and also whether the power button is flashing or not? Please also tell me if you notice any diagnostics LEDs staying lit - these are labelled 1,2,3 and 4 and are near the front headphone sockets.

2) Does the LED on the power supply stay lit if you hold the power supply test button in/

3) Please remove all peripherals at the back of the system and switch the system on. Does this affect the power button LED or diagnostic LEDs?

4) Have you added any components to the system e.g. video cards, sound cards etc...

5) Please open the system and remove the following components:

a) Power and data cables from hard drives and optical drives
b) Any PCI/PCI-Express expansion cards
c) All memory from the system
d) The system fan

6) With the above removed, please reconnect the power cord to the back of the system and switch the system on. Please make a note of what happens with the power button LED and the diagnostic LEDs.

7) If there are no changes to the power button LED or diagnostic LEDs, please remove the power cord from the back of the system and remove the following components:

a) I/O panel cable
b) CMOS battery

8) With the I/O panel cable and CMOS battery removed, please connect the power cord to the back of the system. The system should automatically try to switch on. Do you hear any beeps from the system? If so, can you tell us exactly what you hear?

If you need any assistance removing components, this manual will show you how to do so: <ADMIN NOTE: Broken link has been removed / replaced from this post by Dell>


Please let us know how you get on with the above steps.

speedstep

8 Wizard

 • 

47K Posts

February 1st, 2012 08:00

Contents: Dell Optiplex 755 - Documentation

Which Model?

Dell™ OptiPlex™ 755 User's Guide

 

 Mini Tower Computer <ADMIN NOTE: Broken link has been removed from this post by Dell>

 Desktop Computer <ADMIN NOTE: Broken link has been removed from this post by Dell>

 Small Form Factor Computer <ADMIN NOTE: Broken link has been removed from this post by Dell>

 Ultra Small Form Factor Computer <ADMIN NOTE: Broken link has been removed from this post by Dell>

Diagnostic Lights

CAUTION: Before you begin any of the procedures in this section, follow the safety instructions in the Product Information Guide.

To help troubleshoot a problem, your computer has four lights labeled 1, 2, 3, and 4 on the front panel. When the computer starts normally, the lights flash before turning off. If the computer malfunctions, the sequence of the lights help to identify the problem.

NOTE: After the computer completes POST, all four lights turn off before booting to the operating system.

Light Pattern 

Problem Description

Suggested Resolution

The computer is in a normal off condition or a possible pre-BIOS failure has occurred.

The diagnostic lights are not lit after the computer successfully boots to the operating system.

  • Plug the computer into a working electrical outlet (see Power Problems). <ADMIN NOTE: Broken link has been removed from this post by Dell>
  • If the problem persists, contact Dell (see Contacting Dell).

A possible processor failure has occurred.
  • Reseat the processor (see Processor information for your computer).
  • If the problem persists, contact Dell (see Contacting Dell <ADMIN NOTE: Broken link has been removed from this post by Dell> ).

Memory modules are detected, but a memory failure has occurred.

  • If two or more memory modules are installed, remove the modules (see Removing Memory), then reinstall one module (see Installing Memory) and restart the computer. If the computer starts normally, continue to install additional memory modules (one at a time) until you have identified a faulty module or reinstalled all modules without error.
  • If available, install working memory of the same type into your computer (see Installing Memory).
  • If the problem persists, contact Dell (see Contacting Dell <ADMIN NOTE: Broken link has been removed from this post by Dell> ).

A possible graphics card failure has occurred.
  • Reseat any installed graphics cards (see the "Cards" section for your computer).
  • If available, install a working graphics card into your computer.
  • If the problem persists, contact Dell (see Contacting Dell <ADMIN NOTE: Broken link has been removed from this post by Dell> ).

A possible floppy drive or hard drive failure has occurred.

Reseat all power and data cables.

A possible USB failure has occurred.

Reinstall all USB devices and check all cable connections.

No memory modules are detected.

  • If two or more memory modules are installed, remove the modules (see Removing Memory), then reinstall one module (see Installing Memory) and restart the computer. If the computer starts normally, continue to install additional memory modules (one at a time) until you have identified a faulty module or reinstalled all modules without error.
  • If available, install working memory of the same type into your computer (see Installing Memory).
  • If the problem persists, contact Dell (see Contacting Dell <ADMIN NOTE: Broken link has been removed from this post by Dell> ).

Memory modules are detected, but a memory configuration or compatibility error has occurred.

  • Ensure that no special requirements for memory module/connector placement exist (see Memory).
  • Ensure that the memory you are using is supported by your computer (see the "Specifications" section for your computer).
  • If the problem persists, contact Dell (see Contacting Dell <ADMIN NOTE: Broken link has been removed from this post by Dell> ).

A possible expansion card failure has occurred.

  1. Determine if a conflict exists by removing an expansion card (not a graphics card) and restarting the computer (see the "Cards" section for your computer).
  2. If the problem persists, reinstall the card you removed, then remove a different card and restart the computer.
  3. Repeat this process for each expansion card installed. If the computer starts normally, troubleshoot the last card removed from the computer for resource conflicts (see Troubleshooting Software and Hardware Problems in the Microsoft® Windows® XP and Microsoft Windows Vista® Operating Systems). <ADMIN NOTE: Broken link has been removed from this post by Dell>
  4. If the problem persists, contact Dell (see Contacting Dell <ADMIN NOTE: Broken link has been removed from this post by Dell> ).

Another failure has occurred.

  • Ensure that all hard drive and optical drive cables are properly connected to the system board (see the "System Board Components" section for your computer).
  • If there is an error message on the screen identifying a problem with a device (such as the floppy drive or hard drive), check the device to make sure it is functioning properly.
  • If the operating system is attempting to boot from a device (such as the floppy drive or optical drive), check system setup (see System Setup) to ensure the boot sequence is correct for the devices installed on your computer.
  • If the problem persists, contact Dell (see Contacting Dell <ADMIN NOTE: Broken link has been removed from this post by Dell> ).

Beep Codes

Your computer might emit a series of beeps during start-up if the monitor cannot display errors or problems. This series of beeps, called a beep code, identifies a problem. For example, beep code 1-3-1 (one possible beep code) consists of one beep, a burst of three beeps, and then one beep. This beep code tells you that the computer encountered a memory problem.

Reseating the memory modules may correct the following beep code errors. If the problem persists, contact Dell (see Contacting Dell <ADMIN NOTE: Broken link has been removed from this post by Dell> ) for instructions on obtaining technical assistance.

Code

Cause

1-3-1 through 2-4-4

Memory not being properly identified or used

4-3-1

Memory failure above address 0FFFFh

If you experience any of the following beep code errors, see Contacting Dell <ADMIN NOTE: Broken link has been removed from this post by Dell> for instructions on obtaining technical assistance.

Code

Cause

1-1-2

Microprocessor register failure

1-1-3

NVRAM read/write failure

1-1-4

ROM BIOS checksum failure

1-2-1

Programmable interval timer failure

1-2-2

DMA initialization failure

1-2-3

DMA page register read/write failure

1-3

Video Memory Test failure

1-3-1 through 2-4-4

Memory not being properly identified or used

3-1-1

Slave DMA register failure

3-1-2

Master DMA register failure

3-1-3

Master interrupt mask register failure

3-1-4

Slave interrupt mask register failure

3-2-2

Interrupt vector loading failure

3-2-4

Keyboard Controller Test failure

3-3-1

NVRAM power loss

3-3-2

Invalid NVRAM configuration

3-3-4

Video Memory Test failure

3-4-1

Screen initialization failure

3-4-2

Screen retrace failure

3-4-3

Search for video ROM failure

4-2-1

No timer tick

4-2-2

Shutdown failure

4-2-3

Gate A20 failure

4-2-4

Unexpected interrupt in protected mode

4-3-1

Memory failure above address 0FFFFh

4-3-3

Timer-chip counter 2 failure

4-3-4

Time-of-day clock stopped

4-4-1

Serial or parallel port test failure

4-4-2

Failure to decompress code to shadowed memory

4-4-3

Math-coprocessor test failure

4-4-4

Cache test failure

HeadOnAPike

8 Posts

February 1st, 2012 14:00

1. The power button LED is yellow.  Like I said, the power button only works if you hold the power supply button down first.  However, if you hold the power button down alone it flashes yellow.

2..  Yes, it stays lit.  It also stays lit after I turn it on the aforementioned way.

3.  The only peripheral I had attached was a VGA cable to monitor output.  Removing it does nothing.

4.  The system is stock as far as I know.

5&6.  Removing these still does not allow the computer to be turned on through the power button alone.  I must hold the power supply button first and then press the on button.  Still yellow LED power button, no diagnostic lights, and no video output.

7&8.  I removed the CMOS battery.  I wasn't sure what the I/O Panel Cable was, but I assumed it was component 8 described on page 5 of this link:

www.dell.com/.../opti_755_techspecs.pdf

I plugged the power cable in and it did not try to turn on by itself, there was no beeping either.  The power supply test button still works and turns the power supply LED green, however.

DELL-John C

5 Practitioner

 • 

353 Posts

February 2nd, 2012 03:00

Hi HeadOnAPike,

I think we've ruled it down to two components - either the motherboard itself or the PSU. Can I ask you to remove and reconnect all the power connections from the PSU to the motherboard? On some occasions, a loose connection can cause these problems.

I've also sent you a friend request so I can send you a private message - if you can add me as a friend and give me your service tag by private message, that would be a great help.

HeadOnAPike

8 Posts

February 6th, 2012 10:00

Tried reconnecting all motherboard connections, no dice.  I don't think it's the power supply, forgot to mention that when I press the power supply test button all the fans go on, but I could be wrong.

DELL-John C

5 Practitioner

 • 

353 Posts

February 7th, 2012 02:00

Hi HeadOnAPike,

In this situation, I think I would replace the motherboard. I would say, though, we haven't tried a different power cord. If you have one, I would try connecting the alternative power cord to the system, just to rule out that the power cord is causing this. Also, one other thing, are all the USB ports undamaged? I've seen damaged USB ports causing this issue.

Assuming that it's not the power cord and that there are no damaged USB ports, I think we can say that the motherboard has developed a fault here. Would you like me to find out the cost of a replacement motherboard for you? Please let me know.

HeadOnAPike

8 Posts

February 13th, 2012 15:00

I tried a different power cord, but same thing.  However, one of the USB ports on the front (not on the motherboard) appears to be damaged.  That's on the I/O panel, right?  Could that be the issue?

HeadOnAPike

8 Posts

February 13th, 2012 18:00

Tried a different I/O panel on a different Optiplex 755 on the broken one.  Same problems.  So I doubt the broken USB port on the bad 755 has anything to do with it.  So it looks like we're down to the motherboard here.

HeadOnAPike

8 Posts

February 13th, 2012 18:00

Also, yes, please find out the cost of a replacement motherboard.

speedstep

8 Wizard

 • 

47K Posts

February 14th, 2012 09:00

You didnt say what the diag lights said.

You didnt say you tried ram 1 stick at a time.

If the ram is bad a new motherboard will not help.

If the video card is bad the onboard should still work with vga when the video card is removed.

If the power light is blinking amber — The computer is receiving electrical power, but an internal power problem may exist.

  • Ensure that the voltage selection switch is set to match the AC power at your location (if applicable).
  • Ensure that all components and cables are properly installed and securely connected to the system board (see the "System Board Components" section for your computer).
  • Perform the power supply self-test, if applicable (see Power Supply Self-Test). <ADMIN NOTE: Broken link has been removed from this post by Dell>

If the power light is steady amber — A device may be malfunctioning or incorrectly installed.

  • Ensure that the processor power cable is securely connected to the system board power connector (POWER2) (see the "System Board Components" section for your computer).
  • Remove and then reinstall all memory modules (see Memory).
  • Remove and then reinstall any expansion cards, including graphics cards (see the "Cards" section for your computer).
  • Perform the power supply self-test, if applicable (see Power Supply Self-Test). <ADMIN NOTE: Broken link has been removed from this post by Dell>

DELL-John C

5 Practitioner

 • 

353 Posts

February 16th, 2012 06:00

Hi HeadOnAPike,

What I will say is that the broken USB port on the front I/O panel will require a replacement I/O panel for your system as well as a replacement motherboard - damaged USB ports can cause short circuits which can cause these problems.

I've sent you a private message - if you can reply, it would be very much appreciated.

HeadOnAPike

8 Posts

February 17th, 2012 16:00

Despite the working power supply test button, I tried replacing the power supply anyway just to see.  Lo and behold, it worked!  That button is a little liar.  However, it appears that SATA ports 0, 1 and 2 are broken, and the BIOS only recognizes SATA3.  So I need a new mobo anyway, on top of the power supply, and a new I/O panel it seems....yikes.

HeadOnAPike

8 Posts

March 15th, 2012 16:00

No one quoted my on the price for these parts that I need.

speedstep

8 Wizard

 • 

47K Posts

March 16th, 2012 16:00

This forum is not Sales and Support. There will be no quotes here.

Amazon, Microcenter etc have the entire computer for $200 or less.

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