Previous 1 2 3 4 Next 75 Replies Latest reply: Nov 7, 2013 8:50 PM by marchthefirst Go to original post
  • MotleyPete Level 1 Level 1 (0 points)
    Sorry for the long post, but I've been reading posts/suggestions online and trying a lot of different things, so here are my thoughts/questions.

    This morning I again managed to get my Mac to startup by plugging/unplugging/plugging/unplugging etc. and now that it's running I can shut down and startup fine again (at least, for the rest of the day).

    I ran the Hardware test twice and no problems were flagged up, it told me everything was fine.

    One diagnostic technique I found in the service manual is to startup the Mac with the panel off, restart it by pressing the restart button on the logic board, shutdown using the power button after it's rebooted, then try turning the Mac on normally. The manual says, if you try to startup normally after that (as per the last step) and it doesn't work, you need to replace the power supply. However, it started up normally, so I guess that means I don't need to replace the power supply?

    The other thing suggested was to remove the internal backup battery, leave for about half a minute, then put it back in. I have done that too. Just in case that helps. The next thing I may try is replacing the battery with a new one.

    BTW, when I said "nights sleep" in the post above, I meant me sleeping, not the Mac. I shut my Mac down overnight. However, would it be better to let it sleep? It would certainly be a cheaper than replacing the Power unit or worse, the logic board (which frankly is expensive beyond my means right now). I have after all only had the thing for a couple of years. And this brings up another question, if the logic board and/or power supply is indeed wasted, how come they work fine all day once the Mac is finally running?

    Tonight I will shutdown the Mac and let it go cold, as usual, then see if my efforts so far have helped at all.

    Thanks to you all for your interest and patience. I'll post again tomorrow.
  • Dale Weisshaar Level 6 Level 6 (15,865 points)
    I sleep all three of my macs all the time.

  • MotleyPete Level 1 Level 1 (0 points)

    This morning after a cold startup I had the usual problem, it will try to start up for a second then switches off. I left the machine for about half an hour, it started up for longer, chimed, the grey screen appeared, then it switched itself off again. An hour later I tried again and it started up fine, it's now working for the day and can be shutdown and turned back on again at will. Tomorrow however when it 'cools down' I can safely predict that I will have startup woes again.

    Today I tried checking the Diagnostic LED's on the logic board (another trick from the service manual). Trickle power fine, regular power fine, no nasty red lights signalling failures on the Logic board. According to the logic board & the manual, everything is fine.

    Despite the trickle power being OK I checked to see if the Power Supply Unit was properly connected just in case. It seems to be connected fine.

    _Now for the theorising:_

    It feels almost as if the machine needs to 'warm up' for a little while before it will work. The yellow LED on the Logic Board shows it's correctly receiving trickle power from the PSU when the machine is plugged in (& not on), but obviously not when the power is switched off from the mains supply (which I usually do at night). I've only just found out today that Mac Pro's (& possibly most computers) are never truly turned OFF, unless they are physically disconnected from the mains supply. They still continue to draw a tiny amount of power and trickle it to the Logic board. This is all new to me.

    So, tonight I plan to turn the machine off, but leave the mains supply switched on, so that the PSU continues to supply trickle power to the logic board. Hopefully this will allow my machine to startup from a cold start. It's certainly worth a try anyway.

    Failing that, I could always try sleeping my computer instead of shutting down, but that will only temporarily help until I can afford to fix whatever ails my Mac. Seeing as the diagnostic LED's didn't flag anything up, can I then presume the problem is a failing Power Supply Unit?

    I'll eagerly await to see if the new PSU fixed it for Len. And of course, I'll report back tomorrow to see how tonights 'trickle test' went, If anything to help anone else with the same problem who stumbles across this thread. Of course I also appreciate any input anyone can give me on this. Thanks for reading.
  • jpgav Level 1 Level 1 (0 points)
    I've now bitten the bullet and ordered a new PSU and will get fitted asap once it arrives.

    Will post and let you know if it works!
  • MotleyPete Level 1 Level 1 (0 points)
    I appreciate that jpgav. Thanks

    This morning I haven't been able to get the Mac working yet, although interestingly it seems to start up for few seconds longer than it normally does, before it cuts out again.

    It's looking like I need a new power supply. I think.
  • MotleyPete Level 1 Level 1 (0 points)
    _New Symptom_

    Putting the Mac to sleep causes it to switch off...
  • The hatter Level 9 Level 9 (60,905 points)
    When the Early 2008 first came out, early models needed a EFI firmware update to fix a bug. Wake from sleep would result in freezing.

    It should of course have that update, or shipped with the newer firmware.

    Assume you tried SMC RESET.
  • MotleyPete Level 1 Level 1 (0 points)
    I tried resetting the SMC (unplug, push power button for 5 secs or more, plug back in) but it didn't help I'm afraid.
  • jpgav Level 1 Level 1 (0 points)
    Also have had this problem, in fact since just before the start up problem. Apparently it is common.

    Updated to Snow Leopard latest OX after being advised this would help the sleep did not!

    Not sure if the 2 things are related.

    Mine sleeps after quite a while even though it's set never to sleep!?

    Still waiting for new PSU!
  • MotleyPete Level 1 Level 1 (0 points)
    I managed to get the machine started up again today after a couple of hours of trying again and again. Now, apart from the sleep issue turning it off, it runs like a charm. That's the weird thing that I would love someone to explain. Once it has 'warmed/charged up' it seems quite happy. Why?

    The frustrating thing about this issue is that everywhere online where someone has posted on a message board about this same (or similar) problem the thread invariably goes dead and the person with the problem never reveals what the solution was. Hopefully this thread will rectify the situation.
  • Len Graves Level 1 Level 1 (15 points)
    It has been 5 days since they installed the new power supply, and it seems to have fixed the problem. Will let you know if it starts acting up again.

  • MotleyPete Level 1 Level 1 (0 points)
    Cool, thanks for the update Len. That sounds very encouraging.
  • jpgav Level 1 Level 1 (0 points)
    Got the MAC Pro back this morning after having new PSU fitted and all seems fine!
    Booted straight away and even sleeps/wakes up fine.
    Looks like that was the problem, faulty PSU.

    Have left on today and will keep testing but so far, so good.
  • MotleyPete Level 1 Level 1 (0 points)
    Great news guys, I'm glad your problems are fixed, mine seem to be too.

    I installed a brand new power supply unit myself a couple of days ago and I haven't had the startup problem since (also, sleep works fine too). Unless it crops up again, I guess I can call this one solved.

    Thanks for all your help. It's much appreciated.
  • Maro_jpn Level 1 Level 1 (0 points)
    Hi, looks like I have the same problem as you did. Many 2008s are having the same kind of trouble as I searched solutions on internet.
    I am planning to replace the power supply unit by myself. I have checked eBay and found 2 models for 2008. What is the difference between "614-0409" and "661-4677"? Are they same and interchangeable or should I disassemble mine and check the number on it?
    Thanks for your help.
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