Optiplex GX280 won't turn on

[Jackd]

I've got an Dell Optiplex GX280 which won't turn on. It did turn on a couple of days ago and worked perfectly. Since then I opened it up to add two more sticks of RAM and now it refuses to work with or without the new RAM. As soon as the power supply is plugged into the motherboard an amber light comes on the motherboard and the power button light flashes amber.
According to the dell documentation this means:

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

• Ensure that the voltage selection switch is set to match the AC power at your location (if applicable).
• Ensure that the processor power cable is securely connected to the system board

But i've checked both of those issues.

I've tried it with all the components removed and with a different power supply so does anyone know anything else I can try?

I'm not too bothered if I can't fix it, but it'd be nice.

Thanks

[FN-GM]

With the dells we have at work i have found a flashing orange flight often means a faulty board.

[DrCheese]

Check the capacitors, if any of them are bulging then they are likely causing the problem. Don't forget the ones under the HD tray (if it's the USFF model)
We have had so many of these die recently and flash orange that we ended up buying replacement caps and soldiering replacements on. It usually brings them back to life, but your usage may vary

[MatthewL]

Sounds like board has gone.

[synaesthesia]

I will second DrCheese. Manufacturing fault (of sorts) claimed many Optiplexes including the 280 series. They will either have bulged or "popped" leaving a brown residue.

[NikChillin]

We had this, it was the USB slots shorting out. Someone had bu@@ered up the slot by forcing in a stick the wrong way. Check that the metal teeth arn't touching each other.

[SneakyBeaky]

Try this:
Optiplex GX280 wont boot - Desktop General Hardware Forum - Desktop - Dell Community

[obijon]

Flashing amber is often a failed power supply - easy swap if you have a spare.

[GREED]

We had this, it was the USB slots shorting out. Someone had bu@@ered up the slot by forcing in a stick the wrong way. Check that the metal teeth arn't touching each other.

Absolutely check this, many a time this happened with me. Check front ports especially!!!

[waynebev]

Power supply has blown!! We have had loads of these break at our School!!