G5 U3 Component failure. Any suggestions / POLL ?

Discussion in 'PowerPC Macs' started by spf2, Mar 15, 2017.


Have you had this issue before with one of your G5s ?

Poll closed Mar 15, 2018.
  1. Yes

  2. No

  1. spf2 macrumors regular


    Mar 3, 2015
    Looks like my G5 is experiencing the U3 Memory Controller failure.

    Here is a description of the issue.


    Has anyone had a good experience fixing this or is it just a LB replacement. This G5 has been through a lot but I'm wondering if it is worth continuing. I don't know if I want to invest any more into it. First off, it was a rescue from the recycling center. This G5 had a coolant leak and was stripped of many parts. I bought some cheap replacements from Ebay and it still didn't work. I replaced the 2.5 CPUs with 2.0 ones with heatsinks and made it air cooled. I got it working for a little while and then one of the CPUs died. So I swapped CPU0 and CPU1 and disabled the second processor. It worked for a little while longer. Now, this happens. When I turn it on, I get the 3 pulse power LED flash. I can push on the area to the right of the ram slots and get it to boot but when I remove my finger, the system hangs. Will this eventually happen to all G5's or are there just a few with the defect / issue? Just curious on how many have experienced this.
  2. d-oost macrumors 6502a

    Jan 10, 2016
    Reflowing works, but only temporarily. A LB replacement is the only real way to fix this permanently.

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