> Date: Sun, 31 Oct 1999 20:47:25 -0800
> From: "Timothy A. Seufert" <[EMAIL PROTECTED]>
> Subject: Re: PMU on 2400
>
> At 3:12 PM +0100 10/31/99, Holger Marseille wrote:
>
> If you have a solid green sleep light, the PMU is probably alive, but
> it may have corrupted RAM contents or some such thing. The challenge
> is to reset it, and that can be quite difficult.
>
> >By the way, I tried all this resetting business in all possible
> >combinations, but to no success...
>
> Did you try it a lot? It took me more than 20 tries at resetting the
> PMU to get my 2400 alive once. (Where each try consisted of holding
> the reset button in continuously for 20 seconds or more... sigh.)
>
> >Also in other posts people hinted that even after having their 2400
> >repaired the problems came back. Is this an engineering flaw ?
>
> It's hard for me to tell what the problems people are having really
> are. I *suspect* a lot of the "dead 2400" problems are solvable by
> resetting the PMU. But since the symptoms look like a totally dead
> machine to most people, it usually goes to a repair shop.
When my 2400 died last (end of September, I think?), I spent over an hour
on the phone with Apple, resetting the PMU. FWIW, the Apple tech
recommended resetting with no AC, and with AC but no battery.
I also tried leaving it overnight with no AC or battery, then adding the
battery and resetting. Still no luck, so it went to Apple.
As an engineer, I suspect that the heat dissipation design on the 2400/180
isn't up to snuff, and that the repeated exposure to high temperature over
the course of months or years eventually harms some CPU or CPU daughtercard
components. I've seen hints of this on some Japanese sites, which seem to
say that the problem was fixed in the 2400/240 model.
If all this admitted conjecture is true, an aftermarket mod might help.
MCE, for example, could add a head-conducting shim between the daughtercard
and the chassis (on my unit, they aren't flush).
Possibly the Newer and Vimage daughtercards include this in their design -
but I haven't seen one. Comments from someone who has?
Also, there's the issue of the backup battery. If I understand the design
correctly, the machine won't boot with a dead backup battery. In that case,
does the green light come on? I wouldn't think so, but if it does, then how
can one tell the difference between a corrupt PMU state and a dead backup
battery?
--
Michael Blakeley [EMAIL PROTECTED] <http://www.blakeley.com/>
Performance Analysis for Internet Technologies
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