Optiplex 740 Orange Light

Change the bios coin cell battery first. That keeps the bios settings when the computer is unplugged from power. Check your manual for directions. The coin cell battery can be purchased from any store for ~$2.

The 740 is really old now. Are you sure about the model number? The same advice applies but check the right manual for info.

Hi @Maspuadi,

Mary is right about the size 2032 battery, especially if it's 5 or more years old.  The 740 goes back to 2007 or earlier.  It can be often the first thing to check.  It's a cheap fix even if by chance it doesn't work.

Amber light on the MB (motherboard) means it has power.  That's normal.

Power switch blinking amber means bad PSU.

Power switch steady amber means bad MB.

Optiplex 740 Tech Specs 

Dell Diagnostic Indicators 

I agree. Rock stars are NEVER wrong, and they have massive brains, and know everything.

And you must admit, he has a very old computer that should have been thrown out many years ago.

@bradthetechnut is correct about the amber light.

statistically with these old pc, first thing to go is either psu or motherboard. besides changing cmos battery you can also reset cmos jumper on motherboard to clear cmos settings.

RTCRST - Clears NVRAM. The NVRAM will be cleared when the jumper is closed (use the jumper from the password bridge (PSWD)). To properly clear, AC power must be applied (not necessarily turned on) to the system for about 10 seconds while the jumper is closed. Pins 1-2 once shorted will clear NVRAM and reset all ESCD settings.

Note: You can use the RTCRST jumper procedure above to attempt recovery from a No POST, No Video situation.
The CMOS contains the current BIOS settings. To reset the CMOS and clear those settings:

• Turn off the computer and disconnect the power cable from the electrical outlet.
• Remove the computer cover.
• Locate the 2-pin password connector (PSWD) on the system board.
• Remove the 2-pin jumper plug.
• Locate the 2-pin CMOS jumper (RTCRST) on the system board.
• Move the 2-pin jumper plug from the password jumper to pins into the CMOS jumper.
• Plug in AC power to the system and wait ten seconds for the CMOS to clear.
• Move the 2-pin jumper plug back to the password jumper.

https://www.dell.com/downloads/global/products/optix/en/optix_740_techspecs.pdf

https://www.dell.com/support/article/en-us/sln284985/how-to-perform-a-bios-or-cmos-reset-and-clear-the-nvram-on-dell-systems?lang=en

Wow thank you everyone for the responses, i'm sorry for not replying quick enough. Yes i know that my computer is too old lol, kinda don't have the money to replace it, and i need it to work during the pandemic. I will try every suggestions here, i'll try to reset or change the CMOS battery. Thank you everyone.

You're welcome.