Dimension 2350 blinking motherboard LED - bad power supply
Pretty old news - the machine dates from about 2001 - but I couldn't find exact matches to my situation.
Power switch was OK. Flea power LED on the motherboard was blinking green about 1x/second. No response from the power supply at all. I tried to jump/shunt the green and black wires in the 20-connector harness as described by Bev at http://en.community.dell.com/forums/t/19005769.aspx?c=us&l=en&cs=&s=gen ; no help.
Also walked through the troubleshooting proc at http://support.dell.com/support/topics/global.aspx/support/dsn/en/tree?c=us&l=en&s=gen&journalid=CCB494A12FA411DBA52B951C2F9C46BF&treeid=011360B8243248349C306481A954B356 ("No Power, No Post, No Video") to no avail.
I saw many other posts in here from 2007 about failing power supplies (PSU's). None of the posts described exactly my problem, so I rolled the dice and replaced the power supply. It was the Mitac X-200/12V, which I replaced with a RaidMax ATX12V, model RX-380K. $20-$30 at Fry's.
That solved the problem. This power supply is ATX-compatible. I read that somewhere in this forum, but I can't find the post anymore. Nevertheless, my successful repair substantiates the claim.
I think the PSU failed because of the cabinet in which my family is obliged to store the CPU. It has front closing doors, and my kids frequently leave the machine to go to standby, then somebody walks along and closes the doors. That, and the 1/4 pound of dust bunnies I vacuumed out of the box, probably did the PSU in.
Mind you, many of the complaints elsewhere in this forum are related to a failed motherboard; that was NOT my case, thank goodness. There are a couple of diags in the forum to determine whether it's a motherboard problem.