Optiplex GX300 Blinking Power Button Light

It's either a bad power supply or mainboard -- the former more likely than the latter.  Unfortunately, both the power supply and mainboard are both proprietary and obsolete on this model - you may have difficulty finding either.

Unless the system can't be replaced for some reason, that would be preferable than the seach for parts for this one (which is on the order of 15+ years old).

Thanks for the response. I'd like to get it up and running again. Are there other Dell models that share the same power supply and/or mother board?

There are very few. This is one of the few systems that used RDRAM (the "new" RAM Intel backed, which flopped mightily in the marketplace).  The power supply is proprietary but different from earlier Optiplexes (as well as later ones, which started to use standard ATX units for a time).

You can still find power supplies

www.ebay.com/.../320841547298

Unfortunately, boards are hard to come by -- and complete systems are expensive

www.ebay.com/.../192156530902

likely due to the fact that the vast majority of these were scrapped long ago.

My first Dell was a GX1 mini-tower, similar to the GX300. When I scrapped the GX1, I saved some of the components including the power supply. The GX1 power supply is DP/N 00055079 and the GX300 is DP/N 00055080.  The only difference in the Output Specs are  +5V---/22A for the GX1 and +5V---/29A for the GX300. I'm not sure if they can be swapped permanently but I did give it a try and the light still blinks.

So I am going to look for a mother-board as suggested. Will keep you posted.

DANGER WILL ROBINSON The GX1 has 200W proprietary NPS-200PB-73M 9228C power supply.  This is NOT Compatible with standard ATX and will blow up a standard unit and vice versa.  

Startech made a 300W replacement ATXPW300DELL

This 300 Watt Power Supply is designed as a replacement for specific proprietary Dell computers. It offers dual 12V power rails to deliver stable power to demanding components, and both 20 and 24-pin ATX motherboard power connectors for broad motherboard compatibility.This product is intended for the following systems:Dimension Series Models: 2100 / 4100 / B1000R / L Series / V350 / V400 / XPS B Series / XPS Dxxx / XPS Mxxx / XPS P133c MT / XPS Pro 180n / XPS Rxxx / XPS Txxx;Optiplex Series Models: G1 / GX1 / GX110 / GX115 / GX300 / Gxa / Gxi;Power Edge Series Models: 2100 / 2200;Precision Workstation Series Models: 210 / 400.

http://snpi.dell.com/sna/manuals/A2125383.pdf

It depends on the capacity of the power supply - the wiring is the same but the GX300 came with higher-wattage power supplies than the GX1 did (the boards draw quite a bit more power due to the RDRAM).

Thanks for the warning!

As far as I can tell, nothing "blew up". I am curious though, if the power supply you suggest is compatible with both the GX1 and GX300, why can't power supplies from those two be swapped?

The GX1 has 200W power supply the GX300 needs a 300W power supply.  The startech unit works with both because it has sufficient power.  

Does the GX300 have a standard ATX motherboard? If so, is that what I look for since the power supply seems to be o.k.?

O.K., thanks

The power supply is proprietary and will DESTROY and standard board its hooked up to.