Replacement of logicboard Mac Pro


New Member
Dec 6, 2017
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Hi there,

So im fairly new to the hardware of older Mac's but got my hands in a old Mac Pro 1.1 which was working fine, but definitely lacking power (it was the 2 x dual core version with only 4GB ram). So when i stumbled across some spare parts from a 3.1 I did not hesitate to buy it.
So I took everything out, except the superdrives, harddrive, front panel board and the PSU and put in the following from the 3.1:

- Logic board with CPU's
- Ram risers with new dimms and 4 old dimms

I obviously also fitted heatsinks and so on and attached the wifi antenna to the wifi card (which the 1.1 did not have).

Now I made very sure I got all the cables right, so that should not be the problem.

However when I try to boot it nothing happens except for the following:

1. A VERY short click from somewhere near the front
2. A flash from a red led somewhere in the vicinity of the Wifi card, so at the front of the logicboard. I have tried multiple times to see exactly where but I simply cannot see it because it is so fast.

I have tried pressing the DIAG_LED when the computer having power and the only thing is that the STBY lights yellow which it as fasr as I can tell is supposed to do.

Anyone have any ideas about what could be wrong or suggestions to what I should try? Also, if I left out any important info let me know.


Cory Cooper

May 19, 2004
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Hello and welcome.

The logic board isn't really a user-servicable part. Also, normally they cannot be interchanged within the various models.

-Which exact model Mac Pro?
-Where did you source the replacement logic board and RAM riser?
-How did you attach the heatsinks?

My guess is either the replacement parts are damaged, the PSU isn't strong enough for the new parts, RAM isn't installed correctly, etc.


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