New very old person..Mac keeps switching off..

Hello,

I am an old, new Mac owner of an old Mac.

I have had a second hand Mac OS X 10.5.8 for about 3 months now and love it but because of my great age am not computer literate..in anyway.

My Mac keeps shutting itself down.

I leave it on sleep and return to find it completely shut down and no longer responding keenly to my mouse click.

I have to switch it on using the switch on the back RHS. The grey apple screen appears along with the circular timer thing, then the blue screen, then a tiny almost inaudible pop and it closes down. Sometimes it makes it through to my screen saver and then shuts down. Each time I have to restart it using the switch.

It usually manages to start completely after 3 attempts, screen saver, dock and assorted desktop stuff appears and then I can proceed as normal.

I have read many threads on this forum but my lack of knowledge is so comprehensive that i retreat into gibbering incomprehension and am almost too afraid to ask....

If someone could just point me in the right direction in language suitable for an elderly person to understand I would be most extraordinarily grateful.

Fond regards Ms M

First, Welcome to the Mac Forums.

From your description of the switch location, I assume you own an iMac? If that's not correct, let us know exactly which model Mac you own.

Before we attempt any kind of trouble shooting, lets do a SMC reset. It sounds complicated but really is not. Please follow the directions that are given in this Apple article from their knowledge base. Go to this LINK.

Read through the directions and steps. Note that the SMC reset instructions are different for a portable Mac so be sure to click on the right link to get instructions for your iMac. Let us know if that helped to solve the problem.

Can you describe your iMac a bit more? Is it an LCD screen with white case? When you DO get it to get to the desktop, click on the Apple in the Top Left corner and on About This Mac. Post everything you see there.

My 20" iMac G5 iSight did that very thing and it was a bad Capacitor in the power supply.

Please tell us the info I asked for so we can better help you.

Make sure that the AC power cord is fully pressed into its socket on the back of the iMac.

ron4mac's suggestion is a good one. If that doesn't turn out to be the problem, I believe the issue is a failing power supply.

You will want to take the machine to your local Apple-Authorized Service Provider if it's not the cord issue. On certain older iMacs, the power supply was prone to failure. If I'm correct about the issue any my suspicions about which model it is, it's a pretty easy and relatively inexpensive fix.

Agreed on power supply. I was shocked though that th iSight model I have had some of those bad caps in the supply.

Keep us posted! Try power cord as suggested above. Also more info would still help a bit.