MDD G4s - need to unplug them *every time*?

[CJ_Miller]

Have any of you experienced this with MDDs, or maybe other Macs?

When I power them off after use, I cannot get them to start again until momentarily unplugging the power. This was the case with my old MDD, and my newer FW800. I have had lots of other Macs, but never experienced this problem with any others. Why it's really inconvenient for me is that I have so many old towers that I need to keep them under my desk/table to get them out of the way - it's crowded under there and a bit of a nuisance to need access to the back of the tower every time I use it.

Any ideas of possible causes and/or solutions?

 

[mitchW]

Reset PRAM and check PRAM battery. Also there might be caps inside the PSU going bad, causing erratic power-on/off behavior, but they were not problematic as, for example G5 iMacs.

 

[Hrududu]

Congrats, your power supply is failing.  I'm doing some looking at repairing the Samsung one in my dual 1.25 as we speak.  It used to come on using the button on an ADC display, but i transported it and now it won't boot at all anymore.  My dual 1.42 will still work most of the time, but I have to leave it plugged in all the time.

 

[trag]

Congrats, your power supply is failing.  I'm doing some looking at repairing the Samsung one in my dual 1.25 as we speak.  It used to come on using the button on an ADC display, but i transported it and now it won't boot at all anymore.  My dual 1.42 will still work most of the time, but I have to leave it plugged in all the time.

I've been considering replacing the guts with the guts of a good ATX supply and adding one of these to the 5V standby to supply the 28V circuit:

http://www.ebay.com/itm/351195147071?_trksid=p2060778.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

If one is actually going to use an ADC display, then adding one of these to the 12V circuit (plenty of excess 12V capacity in modern supplies) as well, and isolate each of them with a hefty (high current rating) rectifier:

http://www.ebay.com/itm/191383328623?_trksid=p2060778.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

I won't get to this idea any time soon, so I thought I'd throw it out here for others to try, if they like.

 

[CJ_Miller]

Reset PRAM and check PRAM battery. Also there might be caps inside the PSU going bad, causing erratic power-on/off behavior, but they were not problematic as, for example G5 iMacs.

Yep, this was one problem. I had never checked the battery since I bought this about three years ago, because it looked new. But the battery was in *backwards*! I'm lucky it didn't blow up or something. It didn't solve the problem I was posting about, but thanks for getting me to check something which could have caused a worse problem.

Congrats, your power supply is failing.  I'm doing some looking at repairing the Samsung one in my dual 1.25 as we speak.  It used to come on using the button on an ADC display, but i transported it and now it won't boot at all anymore.  My dual 1.42 will still work most of the time, but I have to leave it plugged in all the time.

Failing to do what, exactly? Mine is the opposite of your 1.42 symptom, I can't leave it plugged in. I suppose I should do a more general search about MDD PSU repair. Feel free to link any you care to recommend.

 

[Schmoburger]

My G3 Yosemite and Yikes G4 both have displayed similar symptoms when the PRAM battery has failed... unsure why, but changing the battery fixed the issue. New world Macs do some strange things when the PRAM battery is getting weak. The G3 also at one point refused to boot properly or even power on sometimes with a flat PRAM battery until i had hit the cuda button on the logic board a couple of times and even at one point had to hold in the interrupt or whatever it is button on the front as if to complete a firmware flash before it would boot after sitting for a while.

Not wanting to fill your head with excessive optimism, as MDD's are known to have issues with PSU's as well, however a PRAM battery is a cheap and easy thing to at least rule out, rather than going straight ahead and replacing or repairing a PSU. Best of luck!