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Re: G5: 3 blinks and no boot [message #33373] Tue, 15 January 2013 23:50 Go to next message
Cameron Kaiser is currently offline  Cameron Kaiser
Messages: 1622
Registered: December 2011
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Senior Member
>>> I think it was the memory controller, partly because it has always been

>>> really hot, between 70 and 75 degrees Celsius

>

>> Wow, that is VERY hot. This quad:

>>

>> Memory cntrlr 54.9 C

>

> Yes it is.

> Since I got it (couple of years ago) it has always been that way.

>

> I cleaned the G5 as best as I could, using a vacuum cleaner (both sucking

> and blowing), but it didn't change the memory controller temp much.

> I probably should disassemble it and check the logic board backside, but

> it's too much hassle for me - I'm not that good with hardware.

> Besides, I'm afraid I could make the LCS leak (this is a Delphi unit, the

> most likely to have leaking issues).

>

> Reading on the Net, lots of people have G5s with the same high temp I have.

> Maybe the Quad G5 had some improvements about airflow/heatsinks.

>

> Apart from disassembling the G5, have you got any suggestion about lowering

> that controller chip's temp?

> It's not getting any airflow there (on the inner side of the board), and I

> think its being so hot has something to do with the "memory error" I just

> got.


The memory controller is a hot part normally, but 70-75 C is searingly so.
The good news is that this is probably *not* the LCS; the LCS cools the CPUs,
not (directly) the rest of the machine.

Assuming this is not a quad, the northbridge for your unit is called U3. It
should be (it's been awhile since I've been inside my folks' dual 2.5, so I'm
going from memory here, ha ha) in the front of the unit under a heat sink
between the RAM DIMMs. The quad has a similar part called U4 in approximately
the same place. IIRC, it is labeled on the board (either U3 or CPC925). U3
and U4 are the parts that are reported as the memory controller.

U3 has a history of overheating (and I hope yours isn't permanently busted).
Check the heat sink and make sure it's not slipped off. Consider removing it,
reapplying thermal paste, reseating the heat sink and putting it through ASD
to make sure there is no permanent damage, assuming it boots.

U4 is a cooler-running part by comparison and on a smaller process size,
which probably accounts for its better longevity. Really, the quad is the
best G5 for so many reasons and here is another.

Here's a MacRumours thread on that, btw:

http://forums.macrumors.com/showthread.php?t=1091176

--
------------------------------------ personal: http://www.cameronkaiser.com/ --
Cameron Kaiser * Floodgap Systems * www.floodgap.com * ckaiser@floodgap.com
-- Traditionally, most of Australia's imports come from overseas. -K. Enderbery

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Re: G5: 3 blinks and no boot [message #33429 is a reply to message #33373] Wed, 16 January 2013 13:20 Go to previous messageGo to next message
Valter Prahlad is currently offline  Valter Prahlad
Messages: 87
Registered: September 2012
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Member
Il giorno 16/01/13 05:50, Cameron Kaiser ha scritto:

> Assuming this is not a quad, the northbridge for your unit is called U3.

Not a quad, it's the Early 2005 2.7 DP.

> U3 has a history of overheating (and I hope yours isn't permanently busted).

No it's not, because both last night and right now the G5 is working.

Thus I think the problem lies in the soldering; the lead-free BGA solder has
become flaky. Heating it with the hair dryer seems making it stable again
(for a while, at least).
Of course, the high temperature of the chip - and consequent stress - only
makes the problem worse.

> Check the heat sink and make sure it's not slipped off. Consider removing it,

> reapplying thermal paste, reseating the heat sink and putting it through ASD

> to make sure there is no permanent damage, assuming it boots.

Good advice but, as I said before, I consider disassembling the G5 my last
possible chance.
Since right now it's working (thanks to the "hair dryer trick"), I don't
want the burden and the risk to disassemble it and - maybe - break something
else. :-/

I was looking for an advice to improve the U3 temp, *without* disassembling
the whole shebang. :-)


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Re: G5: 3 blinks and no boot [message #33431 is a reply to message #33429] Wed, 16 January 2013 13:35 Go to previous messageGo to next message
Charles Lenington is currently offline  Charles Lenington
Messages: 45
Registered: September 2012
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Member
On 1/16/13 12:20 PM, Valter Prahlad wrote:
> Il giorno 16/01/13 05:50, Cameron Kaiser ha scritto:

>


snip-----

> I was looking for an advice to improve the U3 temp, *without* disassembling

> the whole shebang. :-)

>

>


Try tep fan either in bottom of case or on front inside frame. If bottom
use log crews and 2 nuts to hold off bottom for airflow. You will
probably need power cable extension or use a 12 VDC wall wart ran
through a card cover.

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Re: G5: 3 blinks and no boot [message #33464 is a reply to message #33431] Wed, 16 January 2013 14:44 Go to previous messageGo to next message
Charles Lenington is currently offline  Charles Lenington
Messages: 45
Registered: September 2012
Karma: 0
Member
On 1/16/13 12:35 PM, Charles Lenington wrote:
> On 1/16/13 12:20 PM, Valter Prahlad wrote:

>> Il giorno 16/01/13 05:50, Cameron Kaiser ha scritto:

>>

>

> snip-----

>

>> I was looking for an advice to improve the U3 temp, *without*

>> disassembling

>> the whole shebang. :-)

>>

>>

>

> Try tep fan either in bottom of case or on front inside frame. If bottom

> use log crews and 2 nuts to hold off bottom for airflow. You will

> probably need power cable extension or use a 12 VDC wall wart ran

> through a card cover.

>

What?........
tep - should be putting

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Re: G5: 3 blinks and no boot [message #33466 is a reply to message #33429] Wed, 16 January 2013 15:25 Go to previous message
Peter Devlin is currently offline  Peter Devlin
Messages: 13
Registered: December 2012
Karma: 0
Junior Member
On 16/01/2013 18:20, "Valter Prahlad" <valter.prahlad@fastwebnet.it> wrote:

> Of course, the high temperature of the chip - and consequent stress - only

> makes the problem worse.


The high temp of the chip may be due to a poor solder connection - I
have reflowed ball grid arrays on graphics card gpu chips which were faulty
due to heat problems caused by stressed solder joints - strangely enough the
stress was caused by high operating temps due to poor heat dissipation like
a faulty fan or heatsink contact - sometimes the fans and vents were
entirely blocked with dust bunnies and gunk.

Pete


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