Question about Dell OPTIPLEX 960 MT Desktop Computer (Intel Core 2 Duo E8400 250GB2GB) (BO5SC306)

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My optiplex 960 does not turn on. the number 3 flashed for a second. I replaced the motherboard. Now the 3 flashes for a second or two, then turns off and then the 1 and 3 lights blink.

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  • Demetrius Mar 22, 2013

    the power supply is good. i used the on board diagnostic to check it

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Bad capacitors were the bad boys , i have replaced the starting capacitor valued 1000uF 10v just across the switching IC and it worked

Posted on Jun 18, 2016

  • joecoolvette
    joecoolvette Dec 20, 2016

    That's good, however I usually do Not recommend to folks to work on their Power Supply. Cap's hold voltage a LONG time....Yes, they could properly discharge the cap's, but I look towards their safety. (One's that filter the incoming voltage are usually 100 volts...)
    Regards,
    joecoolvette

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  • Dell Master
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Dell Support > Optiplex 960 > Manuals & Documentation tab > Service Manual (6460KB),

http://www.dell.com/support/troubleshooting/us/en/19/Product/optiplex-960

A) "Light Pattern,
Number 3 - Blinking Amber -
A possible motherboard failure has occurred"

This you must have known........however going on.........

"Number 1 and 3 blinking amber -
A possible motherboard, Power Supply, or peripheral failure has occurred"

The first thing to check with desktop computer failure, is the Power Supply.

If we are to agree that using the motherboard diagnostic LED's, and specifically the No.3 LED was blinking Amber; then we can agree it was motherboard failure in the first place.

However, me? I'm a skeptical computer geek.

I ALWAYS, test the Power Supply's 3 main voltage power rails FIRST, then I may go on to assume diagnoses has led to the motherboard, peripherals, etc.

From there, it's check the Radial Aluminum Electrolytic Capacitors on the motherboard, for visual capacitor failure.

The motherboard chipset going out, is a Rarity.
IF, it does fail; it's usually the Northbridge chip of the motherboard chipset; because it get's the hottest.

(That's why it has an aluminum finned Heatsink on it. Sometimes Southbridge chips do too)

Southbridge chip is next in line.

You don't know how many desktop computers, I have fixed over the years; that the problem was the Power Supply, and not the motherboard, as assumed by the owner.

Also it's all over the internet.

LED's light up, and fans spin; and people assume the Power Supply is OK.
This = No.

1) If ALL of the LED's were lit up at once, they would use less than 1 Watt of power.

2) EACH fan uses 2 to 3 Watts of power.

3) A typical Processor (CPU) uses 51 to 130 Watts of power.
Just depends on what Processor it is.

Therefore a Power Supply with a weak voltage power rail, will have PLENTY of power to operate those simpy little Light Emitting Diodes, and maybe spin fans; but will NOT have enough power to turn the Processor on.

Either test the 3 main voltage power rails, with a multimeter set to DC Voltage, (3.3 Volts, 5 Volts, and 12 Volts),
OR,
Use a KNOWN to be good, Compatible power supply; for a temporary test unit.

http://en.wikipedia.org/wiki/Computer_power_supply#Wiring_diagrams

http://www.playtool.com/pages/psuconnectors/connectors.html

Power Supply deemed to be good? Go on with the diagnoses.

Visually inspect the capacitors on the motherboard,

http://capacitorlab.com/visible-failures/index.htm

http://www.youtube.com/watch?v=Lut7MX5Dd_A

What? Are you cra-zy Joe? Did you not read I replaced the motherboard?

Ahem,

That motherboard you have, IF a direct replacement; is an NOS.
New/Old Stock.
Been sitting on a shelf for years.

Point?
Electrolytic Capacitors break down over time. It's the 'nature of the beast'.
They have Electrolytic Paste inside, which is a chemical.
It's known to break down over time.

Computer engineers know this, and use capacitors that are rated at TWICE what is needed. 200 percent.
So..........when the capacitor breaks down to 50 percent good, it is still 100 percent good for the application.

Point?
New purchase, or not IMHO it could be a bad motherboard.

Another point of interest; Electrolytic Capacitors do NOT always show outside visual signs of failure.
The Electrolytic Paste inside can just dry up, instead of developing a gas, (Hydrogen Gas), and not break the seals of the capacitor.

However, I would make sure the power is good, then disconnect all internal peripherals.

Peripherals are also the Harddrive, as well as the optical drive (CD/DVD drive), and Card Reader or Floppy drive.

(Outside peripherals; Keyboard, Mouse, Monitor, Printer, etc.
Leave Keyboard, Mouse, and Monitor of course; but disconnect any other outside peripheral)

That means disconnect the data cable from Harddrive to motherboard, and power cable to Harddrive.
Also same for optical drive/s.

Disconnect, the two cables from the USB header on the motherboard, for the Card Reader. (media)

Floppy Disk Drive data cable, and power cable, IF used.

LEAVE the front computer case fan connected, as it's cooling for the Processor. Ram Memory is installed also.

(NO graphics card if you have installed one. Connect monitor cable back to the motherboard. {Back of computer > I/O area)

So essentially we are talking just Processor, processor fan, and Ram Memory.

Turn the computer on.
Try to pull the BIOS Setup screen, up.

If no, you have a bad motherboard.

Now remember, this is AFTER the Power Supply has been deemed good.

BIOS Setup screen comes up?
Then reconnect the harddrive.
Good to go?

Then reconnect the optical drive. If drives, connect one at a time.
Check.
Then connect the second optical drive.

Good to go?
Then reconnect the card reader.

Had a post from someone on here not long ago; that we went through diagnosing; until he found out the Card Reader was the problem.

If memory serves it was one of the cables, coming from the card reader.

I'm guessing he ran a continuity test on the cable, with a multimeter set to OHM's, to check whether it was indeed the cable; or the USB header on the motherboard it plugged into.

He never stated.

Arranging all that prattle I stated above.......I mean Summation:

1) Test Power Supply voltage power rails, or use KNOWN to be good, Compatible power supply

2) Visually inspect Capacitors on motherboard.

3) Processor, processor fan, Ram Memory, ONLY; see if you can get BIOS Setup screen to come up.

For additional questions please post in a Comment.

Regards,
joecoolvette

Posted on Mar 23, 2013

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Posted on Jan 02, 2017

IB4G2008

Patrick Michaels

  • 3587 Answers

SOURCE: pover up trouble

sounds like something is drawing down on your 12 volt supply drives or on board regulators. Try it without the drives connectged, and see if you can get the system to boot up(you'll just get a notice that your drives are unavailable, but you'll already know that, right?

got backup for your Dell?

Posted on Feb 15, 2008

Anonymous

  • 60 Answers

SOURCE: Dell 5100 won't start... Power button blinks yellow.

hi disconnect pc and try to charge ups without anything connected

Posted on Dec 04, 2008

cpenzes

DEKR

  • 1102 Answers

SOURCE: Dell Optiplex GX150 will not boot - no beeps but has error lights

You first need to make sure your memory is secure.

Posted on Jan 12, 2009

Anonymous

  • 75 Answers

SOURCE: want turn on getting number 1 and 3 flashing

Your Power Supply has gone bad mate... known problem. You need to swap out the old power supply with a new one or maybe a working one (if you have another system)... the procedure is fairly clearly documented on the Dell Site n no Tags needed for that... :-)

Posted on Feb 11, 2009

Current009

Achalesh Prem P

  • 135 Answers

SOURCE: Dell optiplex 330 flashing orange on the power botton

Try to clean the RAM and place it again in the motherboard.

Posted on May 31, 2010

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