696      人物

A1200 iMac black screen fast fans problem

After fitting a known-good replacement hard drive, the iMac when switched on gives these symptoms (which I have read about elsewhere):

     Black screen

     Fans run at full speed

     Front LED bright, steady

     Diagnostic LEDS inside: only first 2 come on

     Pressing power button for several seconds shuts iMac down, leaving one diagnostic LED on

     Numerous SMC resets have had no effect

     Leaving battery out overnight has no effect

     Removing logic board and checking all plugs when reasembling has no effect

     Removing graphics card and refitting carefully has no effect

     All Mosfets near graphics card have likely-looking voltages on them

     There were no graphics irregularities before the failure

     Fitting a different hard drive has no effect

I know that a replacement graphics card or logic board will be recommended, but I hope to find out exactly what is likely to be wrong first. Is it definitely hardware, or can it be anything like firmware? Has anyone ever made a component level repair to put right this failure?

最后更新：2017-10-12 04:58:40

  上一篇： Books sync on Windows with iTunes 12.

  下一篇： create a new shortcut for hibernation